Implementing Fog of War for RTS games in Unity 2/2

As I said in the previous blog post, some time ago I started working on a new Fog of War / Vision System solution aiming the following features:

  • Being able to render the fog of war of each player at any time, for replays and debug.
  • Being able to combine multiple players' visions for alliances, spectator mode or watching replays.
  • Blocking vision by different terrain heights or other elements like bushes.
  • Optimized to support 50+ units at the same time in mobile devices at 60FPS.
  • It should look similar to modern games like Starcraft 2 and League of Legends (in fact, SC2 is already eight years old, not sure if that is consider a modern game or not :P).

This is an example of what I want:

Example: fog of war in Starcraft 2

To simplify a bit writing this article, when I write unit I mean not only units but also structures or anything that could affect the fog of war in the game.

Logic

First, there is a concept named UnitVision used to represent anything that reveals fog. Here is the data structure:

struct UnitVision
{
   // A bit mask representing a group of players inside 
   // the vision system.
   int players;

   // The range of the vision (in world coordinates)
   float range;
   
   // the position (in world coordinates)
   vector2 position;

   // used for blocking vision
   short terrainHeight;
}

Normally, a game will have one for each unit but there could be cases where a unit could have more (for example a large unit) or even none.

A bit mask is used to specify a group of players, so for example, if player 0 is 0001 and player1 is 0010, then 0011 means the group formed by player0 and player1. Since it is an int, it supports up to ~sizeof(int) players.

Most of the time the group would contain only one player but there might be some situations, like a general effect or cinematic, etc, that needs to be seen by all players and one possible solution is to use a unitVision with more than one player.

The terrainHeight field stores the current height of the unit and it is used for blocking vision or not. It normally will be the world terrain's height on that position if it is a ground unit but there are cases like flying units or special abilities that could change the unit height that should be consider when calculating blocked vision. It is the game's responsibility to update that field accordingly.

There is another concept named VisionGrid that represents the vision for all the players. Here is the data structure:

struct VisionGrid
{
    // the width and height of the grid (needed to access the arrays)
    int width, height;

    // array of size width * height, each entry has an int with the 
    // bits representing which players have this entry in vision.
    int[] values;

    // similar to the values but it just stores if a player visited
    // that entry at some point in time.
    int[] visited;

    void SetVisible(i, j, players) {
        values[i + j * width] |= players;
        visited[i + j * width] |= players;
    }

    void Clear() {
        values.clear(0);
    }

    bool IsVisible(i, j, players) {
        return (values[i + j * width] & players) > 0;
    }

    bool WasVisible(i, j, players) {
        return (visited[i + j * width] & players) > 0;
    }
}

Note: arrays have a size of width * height.

The bigger the grid is, the slower it gets to calculate vision but it also has more information which could be useful for units' behaviors or to get better fog rendering.The smaller the grid is, the opposite. A good balance must be defined from the beginning in order to build the game over that decision.

Here is an example of a grid over the game world:

World + Grid

Given a grid entry for a world position, the structure stores an int in the values array with the data of which players have that position inside vision. For example, if the entry has 0001 stored, it means only the player0 sees that point. If it has 0011, then both the player0 and player1.

This structure also stores when a player revealed fog in the past in the visited array which is used mainly for rendering purposes (gray fog) but could also be used by the game logic (to check if a player knows some information for example).

The method IsVisible(i, j, players) will return true if any of the players in the bit mask has the position visible. The method WasVisible(i, j, players) is similar but will check the visited array.

So, for example, if player1 and player2 (0010 and 0100 in bits) are in an alliance, then when player2 wants to know if an enemy is visible to perform an attack, it can call isVisible method with the bitmask for both players 0110.

Calculating vision

Each time the vision grid is updated, the values array is cleared and recalculated.

Here is a pseudo code of the algorithm:

void CalculateVision()
{
   visionGrid.Clear()
   
   for each unitVision in world {
      for each gridEntry inside unitVision.range {
         if (not IsBlocked(gridEntry)) {
            // where set visible updates both the values and the
            // visited arrays.
            grid.SetVisible(gridEntry.i, gridEntry.j, 
                            unitVision.players)
         }
      }
   }
}

To iterate over grid entries inside range, it first calculates vision's position and range in grid coordinates, named gridPosition and gridRange, and then it draws a filled circle of gridRange radius around gridPosition.

Blocked vision

In order to detect blocked vision, there is another grid of the same size with terrain's height information. Here is its data structure:

struct Terrain {
    // the width and height of the grid (needed to access the arrays) 
    int width, height;

    // array of size width * height, has the terrain level of the 
    // grid entry. 
    short[] height;

    int GetHeight(i, j) {
       return height[i + j * width];
    }
}

Here is an example of how the grid looks over the game:

Note: that image is handmade as an example, there might be some mistakes.

While iterating through the vision's grid entries around unitVision's range, to detect if the entry is visible or not, the system checks if there are no obstacles to the vision's center. To do that, it draws a line from the entry's position to the center's position.

If all the grid entries in the line are in the same height or below, then the entry is visible. Here is an example where the blue dot represents the entry being calculated and white dots the line to the center.

If there is at least one entry in the line that is in a greater height, then the line of sight is blocked. Here is an example where the blue dot represents the entry we want to know if it is visible or not, white dots represents entries in the line in the same height and red dots represents entries in a higher ground.

Once it detects one entry above the vision it doesn't need to continue drawing the line to the vision center.

Here is a pseudo algorithm:

public bool IsBlocked()
{
   for each entry in line to unitVision.position {
      height = terrain.GetHeight(entry.position)
      if (height > unitVision.height) {
         return true;
      }
   }
   return false;
}

Optimizations

  • If an entry was already marked as visible while iterating over all unit visions then there is no need to recalculate it.
  • Reduce the size of the grid.
  • Update the fog less frequently (In Starcraft there is a delay of about 1 second, I recently noticed while playing, it is an old game).

Rendering

To render the Fog of War, first I have a small texture of the same size of the grid, named FogTexture, where I write a Color array of the same size using the Texture2D.SetPixels() method.

Each frame, I iterate on each VisionGrid entry and set the corresponding Color to the array using the values and visited arrays. Here is a pseudo algorithm:

void Update()
{
   for i, j in grid {
       colors[i + j * width] = black
       if (visionGrid.IsVisible(i, j, activePlayers))
           colors[pixel] = white
       else if (visionGrid.WasVisible(i, j, activePlayers))
           colors[pixel] = grey // this is for previous vision
   }
   texture.SetPixels(colors)
}

The field activePlayers contains a bit mask of players and it is used to render the current fog of those players. It will normally contain just the main player during game but in situations like replay mode, for example, it can change at any time to render different player's vision.

In the case that two players are in an alliance, a bitmask for both players can be used to render their shared vision.

After filling the FogTexture, it is rendered in a RenderTexture using a Camera with a Post Processing filter used to apply some blur to make it look better. This RenderTexture is four times bigger in order to get a better result when applying the Post Processing effects.

Once I have the RenderTexture, I render it over the game with a custom shader that treats the image as an alpha mask (white is transparent and black is opaque, or red in this case since I don't need other color channels) similar to how we did with Iron Marines.

Here is how it looks like:

Fog texture over the world in game view.

And here is how it looks in the Unity's Scene View:

Fog texture over the world in scene view.

The render process is something like this:

Easing

There are some cases when the fog texture changed dramatically from one frame to the other, for example when a new unit appears or when a unit moves to a higher ground.

For those cases, I added easing on the colors array, so each entry in the array transitions in time from the previous state to the new one in order to minimize the change. It was really simple, it added a bit of performance cost when processing the texture pixels but in the end it was so much better than I preferred to pay that extra cost (it can be disabled at any time).

At first I wasn't sure about writing pixels directly to a texture since I thought it would be slow but, after testing on mobile devices, it is quite fast so it shouldn't be an issue.

Unit visibility

To know if a unit is visible or not, the system checks for all the entries where the unit is contained (big units could occupy multiple entries) and if at least one of them is visible then the unit is visible. This check is useful to know if a unit can be attacked for example.

Here is a pseudo code:

bool IsVisible(players, unit)
{ 
    // it is a unit from one of the players
    if ((unit.players & players) > 0)
        return true;

    // returns all the entries where the unit is contained
    entries = visionGrid.GetEntries(unit.position, unit.size)

    for (entry in entries) {
        if (visionGrid.IsVisible(entry, players)) 
            return true;
    }

    return false;
}

Which units are visible is related with the fog being rendered so we use the same activePlayers field to check whether to show or hide a unit.

To avoid rendering units I followed a similar approach to what we did for Iron Marines using the GameObject's layer, so if the unit is visible, the default layer is set to its GameObject and if the unit is not visible, a layer that is culled from the game camera is set.

void UpdateVisibles() { 
    for (unit in units) { 
        unit.gameObject.layer = IsVisible(activePlayers, unit) : 
                default ? hidden; 
    } 
}

Finally

This is how everything looks working together:

Conclusion

When simplifying the world in a grid and started thinking in terms of textures, it was easier to apply different kind of image algorithms like drawing a filled circle or a line which were really useful when optimizing. There are even more image operations that could be used for the game logic and rendering.

SC2 has a lot of information in terms of textures, not only the player's vision, and they provide an API to access it and it is being used for machine learning experiments.

I am still working on more features and I plan to try some optimization experiments like using c# job system. I am really excited about that one but I first have to transform my code to make it work. I would love to write about that experiment.

Using a blur effect for the fog texture has some drawbacks like revealing a bit of higher ground when it shouldn't. I want to research a bit of some other image effect to apply where black color is not modified when blurring but not sure if that is possible or if it is the proper solution. One thing that I want to try though is an upscale technique like the one used in League of Legends when creating the fog texture and then reduce the applied blur effect, all of this to try to minimize the issue.

After writing this blog post and having to create some images to explain concepts I believe it could be great to add more debug features like showing the vision or terrain grid itself at any time or showing a line from one point to another to show where the vision is blocked and why, among other stuff. That could be useful at some point.

This blog post was really hard to write since, even though I am familiarized with the logic, it was hard to define the proper concepts to be clear when explaining it. In the end, I feel like I forgot to explain some stuff but I can't realize exactly what.

As always, I really hope you enjoyed it and it would be great to hear your feedback to improve writing this kind of blog posts.

Thanks for reading!

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Implementing Fog of War for RTS games in Unity 1/2

For the last 3 years, I've been working on Iron Marines at Ironhide Game Studio, a Real time Strategy Game for mobile devices. During its development, we created a Fog of War solution that works pretty well for the game but it lacks some of the common features other RTS games have, and how to improve that is something I wanted to learn at some point in my life.

Recently, after reading a Riot Games Engineering blog post about Fog of War in League of Legends, I got motivated and started prototyping a new implementation.

In this blog post I will explain Iron Marines' Fog of War solution in detail and then I will write another blog post about the new solution and explain why I consider it is better than the first one.

Fog of War in Strategy Games

It normally represents the missing information about the battle, for example, not knowing how the terrain is yet, or outdated information, for example, the old position of an enemy base. Player units and buildings provide vision that removes Fog during the game revealing information about the terrain and the current location and state of the enemies.

Example: Dune 2 and its Fog of War representing the unknown territory (by the way, you can play Dune 2 online).

Example: Warcraft: Orcs and Humans' Fog of War (it seems you can play Warcraft online too).

The concept of Fog of War is being used in strategy games since more than 20 years now, which is a lot for video games.

Process

We started by researching other games and deciding what we wanted before start implementing anything.

After that, we decided to target a similar solution to Starcraft (by the way, it is free to play now, just download Battle.net and create an account). In that game, units and buildings have a range of vision that provide vision to the Player. Unexplored territory is covered with full opacity black fog while previously explored territory is covered by half opacity fog, revealing what the Player know about it, information that doesn't change during the game.

Enemy units and buildings are visible only if they are inside Player's vision but buildings leave over a last known location after they are not visible anymore. I believe the main reason for that they can't normally move (with the exception of some Terran buildings) so it is logical to assume they will stay in that position after losing vision and might be vital information about the battle.

Iron Marines

Given those rules, we created mock images to see how we wanted it to look in our game before started implementing anything.

Mock Image 1: Testing terrain with different kind of Fog in one of the stages of Iron Marines.

Mock Image 2: Testing now with enemy units to see when they should be visible or not.

Mock Image 3: Just explaining what each Fog color means for the Player's vision.

We started by prototyping the logic to see if it works for our game or not and how we should adapt it.

For that, we used an int matrix representing a discrete version of the game world where the Player's vision is. A matrix's entry with value 0 means the Player has no vision at that position and a value of 1 or greater means it has.

Image: in this matrix there are 3 visions, and one has greater range.

Units and buildings' visions will increment 1 to the value of all entries that represent world positions inside their vision range. Each time they move, we first decrease 1 from its previous position and then we increment 1 in the new position.

We have a matrix for each Player that is used for showing or hiding enemy units and buildings and for auto targeting abilities that can't fire outside Player's vision.

To determine if an enemy unit or building is visible or not, we first get the corresponding entry of the matrix by transforming its world position and check if the stored value is greater than 0 or not. If not, we change its GameObject layer to one that is culled from the main camera to avoid rendering it, we named that layer "hidden". If it is visible, we change it back to the default layer, so it starts being rendered again.

Image: shows how enemy units are not rendered in the Game view. I explain later why buildings are rendered even outside the Player's vision.

Visuals

We started by just rendering a black or grey color quad over the game world for each matrix's entry, here is an image showing how it looks like (it is the only one I found in the chest of memories):

This allowed us to prototype and decide some features we didn't want. In particular, we avoided blocking vision by obstacles like mountains or trees since we preferred to avoid the feeling of confinement and also we don't have multiple levels of terrain like other games do. I will talk more about that feature in the next blog post.

After we knew what we wanted, and tested in the game for a while, we decided to start improving the visual solution.

The improved version consists in rendering a texture with the Fog of War over the entire game world, similar to what we did when we created the visual mocks.

For that, we created a GameObject with a MeshRenderer and scaled it to cover the game world. That mesh renders a texture named FogTexture, which contains the Fog information, using a Shader that considers pixels' colors as an inverted alpha channel, from White color as full transparent to Black color as full opaque.

Now, in order to fill the FogTexture, we created a separated Camera, named FogCamera, that renders to the texture using a RenderTexture. For each object that provides vision in the game world, we created a corresponding GameObject inside the FogCamera by transforming its position accordingly and scaling it based on the vision's range. We use a separated Unity's Layer that is culled from other cameras to only render those GameObjects in the FogCamera.

To complete the process, each of those objects have a SpriteRenderer with a small white Ellipse texture to render white pixels inside the RenderTexture.

Note: we use an Ellipse instead of a Circle to simulate the game perspective.

Image: This is the texture used for each vision, it is a white Ellipse with transparency (I had to make the transparency opaque so the reader can see it).

Image: this is an example of the GameObjects and the FogCamera.

In order to make the FogTexture look smooth over the game, we applied a small blur to the FogCamera when rendering to the RenderTexture. We tested different blur shaders and different configurations until we found one that worked fine on multiple mobile devices. Here is how it looks like:

And here is how the Fog looks like in the game, without and with blur:

For the purpose of rendering previously revealed territory, we had to add a previous step to the process. In this step, we configured another camera, named PreviousFogCamera, using a RenderTexture too, named PreviousVisionTexture, and we first render the visions there (using the same procedure). The main difference is that the camera is configured to not clear the buffer by using the "Don't Clear" clear flag, so we can keep the data from previous frames.

After that, we render both the PreviousVisionTexture in gray color and the vision's GameObjects in the FogTexture using the FogCamera. The final result looks like this:

Image: it shows the revealed territory in the FogCamera.

Image: and here is an example of how the Fog with previous revealed territory looks in the game.

Buildings

Since buildings in Iron Marines are big and they don't move like Starcraft, we wanted to follow a similar solution.

In order to do that, we identified buildings we wanted to show below the Fog by adding a Component and configuring they were going to be rendered when not inside the Player's vision.

Then, there is a System that, when a GameObject with that Component enters the Player's vision for the first time, it creates another GameObject and configures it accordingly. That GameObject is automatically turned on when the building is not inside the Player's vision anymore and turned off when the building is inside vision. If, by some reason the building was destroyed while not in inside vision, the GameObject doesn't disappear until the Player discovers its new state.

We added a small easing when entering and leaving the Player's vision to make it look a bit smoother. Here is a video showing how it looks like:

Conclusion

Our solution lacks some of the common Fog of War features but it works perfectly for our game and looks really nice. It also performed pretty well on mobile devices, which is our main target, and if not done properly it could have affected the game negatively. We are really proud and happy with what we achieved developing Iron Marines.

That was, in great part, how we implemented Fog of War for Iron Marines. I hope you liked both the solution and the article. In the next blog post I will talk more about the new solution which includes more features.

Thanks for reading!

 

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How we used Entity Component System (ECS) approach at Gemserk - 2/2

So, after our first attempt on using ECS, when we started to develop mobile games and moved to the LibGDX framework, we decided to abandon our ComponentsEngine and start over.

We were still reading about ECS while we were creating our set of tools and code over LibGDX. At some point in time, some of the Java community developers started Artemis, a lightweight ECS, and we decided to give it a try.

Artemis

This is a simplified core architecture diagram:

Note: we used a modified version of Artemis with some additions like enable/disable an Entity.

In this pure approach, Entities and Components are just data, and they are related by identifiers, like these tables in a relational database:

Where we have two entities, both with a PositionComponent and only one of them with MovementComponent.

An example of this components in code:

public class PositionComponent : Component {
    public float x, y;
}

public class MovementComponent: Component {
    public float speed;
}

EntitySystems perform the game logic. They normally work on a subset of Components from an Entity but they could need it in order to enable/disable/destroy it (if it is part of its logic).

An example of a System is LimitLinearVelocitySystem, used in multiple of our games to limit the physics velocity of an Entity with PhysicsComponent and LimitVelocityLimitComponent:

public void process(Entity e) {
    PhysicsComponent physicsComponent = 
                     Components.getPhysicsComponent(e);
    Body body = physicsComponent.getPhysics().getBody();

    LinearVelocityLimitComponent limitComponent = 
             e.getComponent(LinearVelocityLimitComponent.class);
    Vector2 linearVelocity = body.getLinearVelocity();

    float speed = linearVelocity.len();
    float maxSpeed = limitComponent.getLimit();

    if (speed > maxSpeed) {
        float factor = maxSpeed / speed;
        linearVelocity.mul(factor);
        body.setLinearVelocity(linearVelocity);
    }
}

There are some extra classes like the TagManager which allows assigning a unique string identifier to an Entity in order to find it, and the GroupManager which allows adding entities to groups identified by a name, which is more like how tags are used everywhere else.

Even though it could look similar to our ComponentsEngine where the Properties in that engine correspond to the Components in this one, and Components to Systems, there is an important difference: Systems are not part of an Entity and work horizontally over all entities with specific Components (data). So, in this approach, changing only data from entities indeed change their behaviour in the game, so it is really data driven.

Since Entities and Components are just data, their instances in memory are easier to reuse. An Entity is just an id, so it is obvious. A Component is a set of data that doesn't care too much which Entity it belongs to. So, after the Entity doesn't need it anymore, it could be reused elsewhere, improving a lot memory usage and garbage collection.

Artemis, and other pure ECS implementations, are really lightweight and performant frameworks. The real power comes from the Systems and Components built over them. In our case, we created a lot of Systems that we started to reuse between games, from SuperFlyingThing to VampireRunner and even in Clash of the Olympians.

Scripting

One of the most interesting ones is the Scripting framework we created over Artemis. It was really useful and gave us a lot of power to overcome some of the limitations we were facing with the pure approach when we need to create a specific logic for a specific moment during the game and (probably) never again and we didn't want a System for that.

They work similar to Unity MonoBehaviours and our logic Components from ComponentsEngine, and they also belong to the Entity lifecycle. One difference, however, is that they try to avoid storing data in their instances as much as possible and instead try to store and read data from Components, like Systems do.

Here is an example Script from one of our games:

public class MovementScript extends ScriptJavaImpl {
	
  @Override
  public void update(World world, Entity e) {

    MovementComponent movementComponent = Components.getMovementComponent(e);
    SpatialComponent spatialComponent = Components.getSpatialComponent(e);
    ControllerComponent controllerComponent = Components.getControllerComponent(e);
		
    Controller controller = controllerComponent.controller;
    Movement movement = movementComponent.getMovement();
    Spatial spatial = spatialComponent.getSpatial();
		
    float rotationAngle = controllerComponent.rotationSpeed * GlobalTime.getDelta();
		
    Vector2 linearVelocity = movement.getLinearVelocity();
		
    if (controller.left) {
        spatial.setAngle(spatial.getAngle() + rotationAngle);
        linearVelocity.rotate(rotationAngle);
    } else if (controller.right) {
        spatial.setAngle(spatial.getAngle() - rotationAngle);
        linearVelocity.rotate(-rotationAngle);
    }
		
  }
	
}

Note: GlobalTime.getDelta() is similar to Unity's Time API.

One problem about the Scripting framework is that it is not always clear when some logic should be in a Script or a System, and that made reusability a bit harder. In the case of the example above, it is obvious it should be moved to a System.

Templates

Another useful thing we did over Artemis was using templates to build entities in a specific way, similar to what we had in ComponentsEngine.

We used also a concept of Parameters in templates in order to customize parts of them. Similar to ComponentsEngine, templates could apply other templates and different templates could be applied to the same Entity.

Here is an example of an Entity template:

public void apply(Entity entity) {

    String id = parameters.get("id");
    String targetPortalId = parameters.get("targetPortalId");
    String spriteId = parameters.get("sprite", "PortalSprite");
    Spatial spatial = parameters.get("spatial");
    Script script = parameters.get("script", new PortalScript());

    Sprite sprite = resourceManager.getResourceValue(spriteId);

    entity.addComponent(new TagComponent(id));
    entity.addComponent(new SpriteComponent(sprite, Colors.darkBlue));
    entity.addComponent(new Components.PortalComponent(targetPortalId, spatial.getAngle()));
    entity.addComponent(new RenderableComponent(-5));
    entity.addComponent(new SpatialComponent(spatial));
    entity.addComponent(new ScriptComponent(script));

    Body body = bodyBuilder //
            .fixture(bodyBuilder.fixtureDefBuilder() //
                    .circleShape(spatial.getWidth() * 0.35f) //
                    .categoryBits(CategoryBits.ObstacleCategoryBits) //
                    .maskBits((short) (CategoryBits.AllCategoryBits & ~CategoryBits.ObstacleCategoryBits)) //
                    .sensor()) //
            .position(spatial.getX(), spatial.getY()) //
            .mass(1f) //
            .type(BodyType.StaticBody) //
            .userData(entity) //
            .build();

    entity.addComponent(new PhysicsComponent(new PhysicsImpl(body)));

}

That template configures a Portal entity in SuperFlyingThing which teleports the main ship from one place to another. Click here for the list of templates used in that game.

Interacting with other systems

Sometimes you already have a solution for something, like the physics engine, and you want to integrate it with the ECS. The way we found was to create a way to synchronize data from that system to the ECS and vice versa, sometimes having to replicate a bit of data in order to have it easier for the game to use it.

Finally

Even though we had to do some modifications and we know it could still be improved, we loved using a pure ECS in the way we did.

It was used to build different kind of games/prototypes and even a full game like the Clash of the Olympians for mobile devices, and it worked pretty well.

What about now?

Right now we are not using any of this in Unity. However we never lost interest nor feith in ECS, and there are starting to appear new solutions over Unity in the last years that caught our attention. Entitas is one of them. The Unity team is working towards this path too as shown in this video. Someone who din't want to wait started implementing that solution in his own way. We've also watched some Unite and GDC talks about using this approach in big games and some of them even have a Scripting layer too, which is awesome since, in some way, it validates we weren't so wrong ;).

I am exited to try ECS approach again in the near future. I believe it could be a really good foundation for multiplayer games and that is something I'm really interested in doing at some point in my life.

Thanks for reading.

References

 

 

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How we used Entity Component System (ECS) approach at Gemserk - 1/2

When we started Gemserk eight years ago, we didn't know which was the best way to make games. So before starting, we did some research. After reading some articles and presentations we were really interested in trying an Entity Component System (ECS) approach for our games. However, since we didn't find a clear guide or implementation at that point we had to create our own solution while exploring and understanding it. We named our engine ComponentsEngine.

Components Engine

The following image shows a simplified core architecture diagram:

Note: part of the design was inspired by a Flash ECS engine named PushButtonEngine.

An Entity is just a holder of state and logic. In an ECS, anything can be an Entity, from an enemy ship to the concept of a player or even a file path to a level definition. It depends a lot on the game you are making and how you want to structure it.

A Property is part of the state of an Entity, like the health or the position in the world, anything that means something for the state of the game. It can be accessed and modified from outside.

Components perform logic updating one or more Properties to change the Entity state. A component could for example change the position of an Entity given a speed and a moving direction.

They normally communicate with each other either by modifying common Properties (when on the same Entity) or by sending and receiving Messages through a MessageDispatcher (when on the same or on different Entities). They just have to register a method to handle a message. In some way, this is pretty similar to using SendMessage() method in Unity and having the proper methods in the MonoBehaviours that need to react to those messages.

EntityTemplates are an easy way to define and build specific game entities, they just add Properties and Components (and more stuff) to make an Entity behave in one way or another.

For example, a ShipTemplate could add position, velocity and health properties and some components to perform movement and to process damage from bullet hits:

public void build() {
        // ... more stuff 
        property("position", new Vector2f(0, 0));
        property("direction", new Vector2f(1, 0));

        property("speed", 5.0f);

        property("currentHealth", 100.0f);
        property("maxHealth", 100.0f);

        component(new MovementComponent());
        component(new HealthComponent());
}

An example of the MovementComponent:

public class MovementComponent() {

   @EntityProperty
   Vector2f position;

   @EntityProperty
   Vector2f direction;

   @EntityProperty
   Float speed;

   @Handles
   public void update(Message message) {
      Property<Float> dt = message.getProperty("deltaTime");
      position += direction * speed * dt.get();
   }

}

In some way, EntityTemplates are similar to Unity Prefabs or Unreal Engine Blueprints, represeting in some way a (not pure) Prototype pattern.

Some interesting stuff of our engine:

  • Since templates are applied to Entities, we can apply multiple templates to the same one. In this way, we could have common templates to add generic features like motion for example. So we could do something like OrcTemplate.apply(e) to add the orc properties and components and then MovableTemplate.apply(e), so now we have an Orc that moves.
  • Templates can apply other templates inside them. So we could do the same as before but inside OrcTemplate, we could apply MovableTemplate there. Or even use this to create specific templates, like OrcBossTemplate which is an Orc with a special ability.
  • Entities have also tags which are defined when applying a template too and are used to quickly identify entities of interest. For example, if we want to identify all bullets in the game, we could add the tag "Bullet" during the Entity creation and then, when processing a special power, we get all the bullets in the scene and make them explode. Note: in some ECS a "flag" component is used for this purpose.
  • The Property abstraction is really powerful, it can be implemented in any way, for example, an expression property like "my current health is my speed * 2". We used that while prototyping.

Some bad stuff:

  • Execution speed wasn't good, we had a lot of layers in the middle, a lot of reflection, send and receive messages (even for the update method), a lot of boxing and unboxing, etc. It worked ok in desktop but wasn't a viable solution for mobile devices.
  • The logic started to be distributed all around and it wasn't easy to reuse, and we started to have tons of special cases, when we couldn't reuse something we simply copy-pasted and changed it.
  • There was a lot of code in the Components to get/set properties instead of just doing the important logic.
  • Indirection in Properties code was powerful but we end up with stuff like this (and we didn't like it since it was too much code overhead):
e.getProperty("key").value = e.getProperty("key").value + 1.
  • We didn't manage to have a good data driven approach which is one of the best points of ECS. In order to have different behaviours we were forced to add both properties, components and even tags instead of just changing data.

Note: Some of these points can be improved but we never worked on that.

Even though we don't think the achitecture is bad, it guided us to do stuff in a way we didn't like it and didn't scale. We feel that Unity does the same thing with its GameObjects and MonoBehaviours, all the examples in their documentation go in that direction.

That was our first try to the ECS approach. In case you are interested, ComponentsEngine and all the games we did with it are on Github and even though they are probably not compiling, they could be used as reference.

This post will continue with how we later transitioned to use a more pure approach with Artemis, when we were more dedicated to mobile games.

References

Evolve your hierarchy - Classic article about Entity Component System.

PushButtonEngine - Flash Entity Component System we used as reference when developing our ComponentsEngine.

Game architecture is different - A quick transformation from normal game architecture to ECS.

Slick2D - The game library we were using during ComponentsEngine development.

 

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Assigning interface dependencies to MonoBehaviour fields in Unity Editor

In Unity, Object's public fields of type interface are not serialized, so that means it is not possible to configure them using the editor like you do with other stuff like dependencies to MonoBehaviours.

One possible way to deflect this problem is to create an abstract MonoBehaviour and depend on that instead:

 public abstract class ServiceBase : MonoBehaviour
 {
     public abstract void DoStuff();    
 }
 
 public class ServiceUser : MonoBehaviour
 {
     public ServiceBase service;
 
     void Update()
     {
         service.DoStuff ();
     }
 }

This solution has some limitations. One of them is you can't create a sub class of multiple base classes like you do when implementing interfaces. Another limitation is that you can't easily switch between a MonoBehaviour implementation to a ScriptableObject implementation (or any other).

Working on Iron Marines and Dashy Ninja, I normally end up referencing a UnityEngine.Object and then in runtime I try to get the specific interface, like this:

 public interface IService 
 {
      void DoStuff();
 }
 
 public class CharacterExample : MonoBehaviour
 {
     public UnityEngine.Object objectWithInterface;
     IService _service;
 
     void Start ()
     {
         var referenceGameObject = objectWithInterface as GameObject;
         if (referenceGameObject != null) {
             _service = referenceGameObject.GetComponentInChildren<IService> ();
         } else {
             _service = objectWithInterface as IService;
         }
     }

     void Update()
     {
         _service.DoStuff ();
     }
 }
 

Then, in Unity Editor I can assign both GameObjects and ScriptableObjects (or any other Object):

That works pretty well but I end up having the code of how to get the interface duplicated all around.

To avoid that, I made up two helper classes with the code to retrieve the interface from the proper location. These are InterfaceReference and InterfaceObject<T>.

InterfaceReference

 [Serializable]
 public class InterfaceReference
 {
     public UnityEngine.Object _object; 
     object _cachedGameObject;
 
     public T Get<T>() where T : class
     {
         if (_object == null)
             return _cachedGameObject as T;

         var go = _object as GameObject;
 
         if (go != null) {
             _cachedGameObject = go.GetComponentInChildren<T> ();
         } else {
             _cachedGameObject = _object;
         }
 
         return _cachedGameObject as T;
     }

     public void Set<T>(T t) where T : class
     {
         _cachedGameObject = t;
         _object = t as UnityEngine.Object;
     }
 }

Usage example:

 public class CharacterExample : MonoBehaviour
 {
     public InterfaceReference service;
 
     void Update()
     {
         // some logic
         service.Get<IService>().DoStuff();
     }
 }

The advantage of this class is that it could be simply used anywhere and it is already serialized by Unity. But the disadvantage is having to ask for specific interface when calling the Get() method. If that is only in one place, great, but if you have to do it a lot in the code it doesn't look so good. In that case, it could be better to have another field and assign it once in Awake() or Start() methods.

InterfaceObject

 public class InterfaceObject<T> where T : class
 {
     public UnityEngine.Object _object;
     T _instance;
 
     public T Get() {
         if (_instance == null) {
             var go = _object as GameObject;
             if (go != null) {
                 _instance = go.GetComponentInChildren<T> ();
             } else {
                 _instance = _object as T;
             }
         }
         return _instance;
     }
 
     public void Set(T t) {
         _instance = t;
         _object = t as UnityEngine.Object;
     }
 }

Note: the Get() and Set() methods could be a C# Property also, which would be useful to allow the debugger to evaluate the property when inspecting it.

Usage example:

 [Serializable]
 public class IServiceObject : InterfaceObject<IService>
 {
     
 }
 
 public class CharacterExample : MonoBehaviour
 {
     public IServiceObject service;
 
     void Update()
     {
         // some logic
         service.Get().DoStuff();
     }
 }

The advantage of this class is that you can use the Get() method without having to cast to the specific interface. The disadvantage, however, is that it is not serializable because it is a generic class. In order to solve that, an empty implementation with a specific type must be created to allow Unity to serialize it, like it is shown in the previous example. If you don't have a lot of interfaces you want to configure, then I believe this could be a good solution.

All of this is simple but useful code to help configuring stuff in the Unity Editor.

I am working on different experiments on how to improve Unity's usage for me. Here is a link to the project in case you are interested in taking a look.

Thanks for reading

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We are working on a new Game for mobile devices named Dashy Ninja

After the last Ludum Dare#38 we were really excited about what we accomplished and decided to work on something together in our spare time. So, we started working on a new Unity game for mobile devices currently named Dashy Ninja.

This game is about a Cat facing the most difficult and challenging trials to achieve the unachievable and go where no other Cat has gone before to become the ultimate Ninja Cat.

The mechanics of the game are simple, by making quick drag gestures the cute cat dashes through the level attaching itself to platforms on the way. If a trap gets the character, it is "magically teleported back" (no animals were harmed in the making this blog post) and starts over again. The player has to feel as Ninja as possible.

We wanted to make a proper introduction of the game so we can start sharing dev stuff of the most awesome Ninja Cat in the Universe.

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Our tips to improve Unity UI performance when making games for mobile devices

There is a Unity Unite talk named "Unite Europe 2017 - Squeezing Unity: Tips for raising performance" by Ian Dundore about things you can do in your game to improve Unity performance by explaining how Unity works behind the scenes.

Update: I just noted (when I was about to complete the post) there is another talk by Ian from Unite 2016 named "Unite 2016 - Let's Talk (Content) Optimization", which has other good tips as well.

There are two techniques to improve Unity UI performance we use at work they didn’t mention in the video and we want to share them in this blog post. One of them is using CanvasGroup component and the other one is using RectMask2D.

CanvasGroup

CanvasGroup component controls the alpha value of all the elements inside in its RectTransform hierarchy and whether that hierarchy handle input or not. The first one is mainly used for render purposes while the second one for user interaction.

What is awesome about CanvasGroup is, if you want to avoid rendering a hierarchy of elements, you can just put alpha in 0 and that will avoid sending it to render queue improving gpu usage, or at least that is what the FrameDebugger and our performance tests say. If you also want to avoid that hierarchy to consume events from the EventSystem, you can turn off the block raycast property and that will avoid all the raycast checks for its children, improving cpu usage. The combination of those two is important. It is also easier and more designer friendly than iterating over all the children with CanvasRender and disable them. Same thing to disable/enable all objects handling raycasts.

In our case, at work, we are using multiple Canvas objects and have all of them “disabled” (not being rendered nor handling input) using CanvasGroup alpha and block raycasts properties. That improves a lot the speed of activating and deactivating our metagame screens since it avoids regenerating the mesh and calculating layout again which GameObject SetActive() does.

RectMask2D

The idea when using masks it to hide part of the screen in some way, even using particular shapes. We use masks a lot at work in the metagame screens, mainly to show stuff in a ScrollRect in a nice way.

We started using just Mask component, with an Image without Sprite set, to crop what we wanted. Even though it worked ok, it wasn’t performing well on mobile devices. After investigating a bit with FrameDebugger we discovered we had tons of render calls of stuff that was outside the ScrollRect (and the mask).

Since we are just using rectangle containers for those ScrollRects, we changed to use RectMask2D instead. For ScrollRects with a lot of elements, that change improved enormously the performance since it was like the elements outside the mask weren’t there anymore in terms of render calls.

This was a great change but only works if you are using rectangle containers, doesn’t work with other shapes. Note that the Unity UI Mask tutorial only shows image masks and doesn't say anything about performance cost at all (it should).

Note: when working with masks there is a common technique of adding something over the mask to hide possible ugly mask borders, we normally do that on all our ScrollRect that doesn't cover all the screen.

Bonus track: The touch hack

There is another one, a hack, we call it the Touch Hack. It is a way to handle touch all over the screen without render penalty, not sure it is a great tip but it helped us.

The first thing we thought when handling touch all over the screen (to do popup logic and/or block all the other canvases) was to use an Image, without Sprite set, expanded to all the screen with raycast enabled. That worked ok but it was not only breaking the batch but also rendering a big empty transparent quad to all the screen which is really bad on mobile devices.

Our solution was to change to use a Text instead, also expanded to all the screen but without Font nor text set. It doesn’t consume render time (tested on mobile devices) and handles the raycasts as expected, I suppose it is because it doesn’t generate the mesh (since it doesn’t have text nor font set) and at the same time still has the bounding box for raycasts configured.

Conclusion

It is really important to have good tools to detect where the problems are and a way to know if you are improving or not. We use a lot the FrameDebugger (to see what was being drawn, how many render calls, etc), the overdraw Scene view and the Profiler (to see the Unity UI CPU cost).

Hope these tips could help when using Unity UI to improve even more the performance of your games.

More

Optimizing Unity UI - http://www.tantzygames.com/blog/optimizing-unity-ui/

A guide to optimizing Unity UI - https://unity3d.com/es/learn/tutorials/temas/best-practices/guide-optimizing-unity-ui

Implementing Multiple Canvas Groups In Unity 5 - http://www.israel-smith.com/thoughts/implementing-multiple-canvas-groups-in-unity-5/

 

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Pigs Mayhem in Space, our Ludum Dare Jam #38 entry

After some years of Ludum Dare (LD from now on) inactivity, we decided to participate in LD #38 Jam. And when I say we I mean Rubén and I! Of course, since we are great artists, we joined forces with Thony, a young artist who is really really good (just open the link and see it by yourself).

The theme of this LD was "A small world" and our game was Pigs Mayhem in Space:

After iterating over a thousand ideas (yeah, I like to exaggerate, they were only 999) the first day, we ended up with a 3d, turn by turn game where you have to use projectiles and physics to kill the other players (like Worms). This is one of the first concept:

And this is the how the game looked at the end:

Play the game!

Small post mortem

The bad

  • It took us a lot of time to define the game, and that means we did a lot of work on stuff we didn't use.
  • We didn't spend time polishing the controls and when we wanted it was already too late. That affected a lot the game experience.

The good

  • We were aligned with the game we wanted to do and with almost every decision.
  • The art style was quickly defined and without setbacks. It helped a lot to visualize the final game.
  • Working together was really smooth, the game was first and all decisions were to make the game better.

Conclusion

Even though Rubén and I work together at Ironhide, we are not in the same team and even though we share stuff between projects, I missed a lot working directly with him in the same project, since, you know, we fight discuss a lot but the results are always better 🙂

This was my first time working with Thony (Rubén and Thony work in the same team at Ironhide) and it was prety awesome. He has good control on 3d tools and Unity and does great 2d art (the game proves it!).

As always, it was a great experience, it helped on exercising the creative process of developing games and learning how different kind of games are made.

Links

The game at itchio

Thony's ArtStation page

Some visual references

 

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Playing with Starcraft 2 Editor to understand how a good RTS is made

When working on Iron Marines engine at work we did some research on other RTS games in order to have more knowledge on how they did some stuff and why. In this post, in particular, I want to share a bit of my research on the SC2 Editor which helped a lot when making our own editor.

The objective was to see what a Game Designer could do or not with the SC2 Editor in order to understand some decisions about the editor and the engine itself.

Obviously, by taking a look at the game mods/maps available it is clear that you could build entire games over the SC2 engine, but I wanted to see the basics, how to define and control the game logic.

As a side note, I love RTS games since I was a child, I played a lot of Dune 2 and Warcraft 1. I remember playing with the editors of Command & Conquer and Warcraft 2 also, it was really cool, so much power 😉 and fun. With one of my brothers, each one had to make a map and the other had to play and beat it (we did the same with Doom and Duke Nukem 3d editors).

SC2 Editor

SC2 maps are built with Triggers which are composed by Events, Conditions and Actions to define parts of the game logic. There are a lot of other elements as well that I will talk a bit after explaining the basics.

Here is an image of the SC2 Editor with an advanced map:

Trigger logic

The Triggers are where the general map logic is defined. They are triggered by Events and say which Actions should be performed if given Conditions are met. Even though behind the scenes the logic is C/C++ code and it is calling functions with similar names, the Editor shows it in a natural language like “Is Any Unit of Player1 Alive?” which helps for quick reading and understanding.

This is an example of a Trigger logic of a SC2 campaign map:

Events

Events are a way to Trigger the Trigger logic, in other words, when an event happens the logic is executed. Here is an example of an event triggered when the unit "SpecialMarine" enters the region "Region 001":

Conditions

Conditions are evaluated in order to execute the actions or not. Here is an example of a condition checking if unit "BadGuy" is alive or not:

Actions

Actions are executed when the event happened and the conditions are met. They could be anything supported by the editor, from ordering a structure to build a unit to showing a mission objective update on screen, among other things.

This example shows an action that enqueues to unit "BadGuy" an attack order with unit "SpecialMarine" as target, replacing existing enqueued orders in that unit. There is another action after that which turns off the Trigger in order to avoid processing its logic again.

The idea with this approach is to build the logic in a descriptive way, the Game Designer has tools to fulfill what he needs in terms of game experience. For example, he needs to make it hard to save a special unit when you reach its location, then he sends a wave of enemies to that point.

I said before that the editor generates C/C++ code behind the scenes, so, for my example:

The code generated behind the scenes is this one:

Here is a screenshot of the example I did, the red guy is the SpecialMarine (controlled by the player) and the blue one is the BadGuy (controlled by the map logic), if you move your unit inside the blue region, BadGuy comes in and attack SpecialMarine:

Even though it is really basic, download my example if you want to test it 😛 .

Parameters

In order to make the Triggers work, they need some values to check against, for example, Region1, is a region previously defined, or “Any Unit of Player1”. Most of the functions for Events, Conditions and Actions have parameters of a given Type, and the Editor allow the user to pick an object of that Type from different sources: a function, a preset, a variable, a value or even custom code:

It shows picking a Unit from units in the map (created instances).

It shows Unit picking from different functions that return a Unit.

This allows the Game Designer to adapt, in part, the logic to what is happening in the game while keeping the main structure of the logic. For example, I need to make the structures of Player2 explode when any Unit of Player1 is in Region1, I don’t care which unit I only care it is from Player1.

Game design helper elements

There are different elements that help the Game Designer when creating the map: Regions, Points, Paths and Unit Groups, among others. These elements are normally not visible by the Player but are really useful to the Game Designer to have more control over the logic.

As said before, the SC2 Editor is pretty complete, it allows you to do a lot of stuff, from creating custom cutscenes to override game data to create new units, abilities, and more but that's food for another post.

Our Editor v0.1

The first try of creating some kind of editor for our game wasn't so successful. Without the core of the game clearly defined we tried to create an editor with a lot of the SC2 Editor features. We spent some days defining a lot of stuff in abstract but in the end we aimed too far for a first iteration.

So, after that, we decided to start small. We starting by making a way to detect events over the "being defined core" at that point. An event could be for example: "when units enter an area" or "when a resource spot was captured by a player".

Here are some of the events of one of our maps:

Note: Even though they are Events we named them Triggers (dunno why), so AreaTrigger is an empty Trigger in terms of SC2 Editor with just an Event.

Events were the only thing in the editor, all the corresponding logic was done in code in one class, corresponding to that map, which captures all events and checks conditions for taking some actions, normally, sending enemies to attack some area.

Here is an example code for some of the previous defined events:

It wasn't a bad solution but had some problems:

  • The actions were separated from the level design which played against the iteration cycle (at some point our project needed between 10 and 15 seconds to compile in the Unity Editor).
  • Since it needs code to work, it requires programming knowledge and our team Game Designers aren't so good with code.

Our Editor v0.2

The second (and current) version is more Game Designer friendly, and tends to be more similar to SC2 Editor. Most of the logic is defined in the editor within multiple triggers. Each Trigger is defined as a hierarchy of GameObjects with specific components to define the Events, Conditions and Actions.

Here is an example of a map using the new system:

This declares for example a trigger logic that is activated by time, it has no conditions (so it executes always given the event) and it sends some enemies in sequence and deactivates itself at the end.

We also created a custom Editor window in order to help creating the trigger hierarchy and to simplify looking for the engine Events, Conditions and Actions. Here is part of the editor showing some of the elements we have:

All those buttons automatically create the corresponding GameObject hierarchy with the proper Components in order to make everything work according to plan. Since most of them need parameters, we are using the Unity built-in feature of linking elements given a type (a Component), so for example, for the action of forcing capture a Capturable element by team Soldiers, we have:

Unity allow us to pick a Capturable element (CapturableScript in this case) from the scene. This simplifies a lot the job of configuring the map logic.

Some common conditions could be to check if a resource spot is controlled by a given player or if a structure is alive. Common actions could be, send a wave of enemy units to a given area or deactivate a trigger.

The base code is pretty simple, it mainly defines the API while the real value of this solution is in the custom Events, Conditions and Actions.

Pros

  • Visual, and more Game Designer friendly (it is easier for Programmers too).
  • Faster iteration speed, now we can change things in Editor directly, even in runtime!
  • Easily extensible by adding more Events, Conditions and Actions, and transparent to the Game Designers since they are automatically shown in our Custom Editor.
  • Take advantage of Unity Editor for configuring stuff.
  • Easy to disable/enable some logic by turning on/off the corresponding GameObject, which is good for testing something or disable one logic for a while (for example, during ingame cinematics).
  • More control to the Game Designer, they can test and prototype stuff without asking programming team.
  • Simplified workflow for our ingame cinematics.
  • Compatible with our first version, both can run at the same time.

Cons

  • Merge the stage is harder now that it is serialized with the Unity scene, with code we didn’t have merge problems or at least it was easier to fix. One of the ideas to simplify this is to break the logic in parts and use prefabs for those parts, but it breaks when having links with scene instances (which is a common case).
  • A lot of programming responsibility is transferred to the scripting team which in this case is the Game Design team, that means possibly bad code (for example, duplicated logic), bugs (forget to turn off a trigger after processing the actions) and even performance.

Conclusion

When designing (and coding) a game, it is really important to have a good iteration cycle in each aspect of the game. Having switched to a more visual solution with all the elements at hand and avoiding code as much as we could, helped a lot with that goal.

Since what we end up doing looks similar to a scripting engine, why didn't we go with a solution like uScript or similar in the first place? the real answer is I didn't try in depth other Unity scripting solutions out there (not so happy with that), each time I tried them a bit they gave me the feeling it was too much for what we needed and I was unsure how they perform on mobile devices (never tested that). Also, I wasn't aware we would end up need a scripting layer, so I prefered to evolve over our needs, from small to big.

Taking some time to research other games and play with the SC2 Editor helped me a lot when defining how our engine should work and/or why we should go in some direction. There are more aspects of our game that were influenced in some way by how other RTS games do it, which I may share or not in the future, who knows.

I love RTS games, did I mention that before?

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Using Unity Text to show numbers without garbage generation

The idea of this post is to show different ideas and analysis on how to use Unity UI Text to show numbers without garbage generation. I need this for a framerate counter and other debug values.

Test case

Shows a fixed digit length number in screen, regenerated each frame with a new random value.

Shows how the test scene used for all test cases work.

Using Strings

Since strings are immutable in c#, common operations on strings generates new strings and hence allocates new heap memory. If you are using strings as temporary values like showing a changing number in a UI text then that memory becomes garbage. In PC that garbage could go unnoticed but not in mobile devices since that could derive in a hiccup when the garbage collector decides to collect it.

The idea with these tests is to try to use make the label work with strings without garbage generation. To detect generated garbage I am using the Unity profiler and avoiding ToString() of int, float, etc, to just calculate the cost of the string manipulation for now.

String concatenation

String concatenation generates 30 Bytes per frame since internally String.Concat() calls String.InternallyAllocateStr().

It is not as bad as expected, it is just creating a new string with the length of the first string plus the second and then it copies their values. Obviously it becomes worse when multiple concatenations are done in secuence.

Test code:

Text text;
 
static readonly string[] numbers = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
 
void Start () {
    text = GetComponent<Text> ();
}
 
void Update () {
     
    string a = numbers[UnityEngine.Random.Range(0, numbers.Length)];
    string b = numbers[UnityEngine.Random.Range(0, numbers.Length)];
 
    text.text = a + b;
}

String format

Using string.Format() generates 176 Bytes per frame, internally is using String.FormatHelper + StringBuilder.ToString().  The first one creates a new StringBuilder and the second is the transform from StringBuilder to string.

Test code:

 Text text;
 
 static readonly string[] numbers = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
 
 void Start () {
     text = GetComponent<Text> ();
 }
 
 void Update () {
     string a = numbers[UnityEngine.Random.Range(0, numbers.Length)];
     string b = numbers[UnityEngine.Random.Range(0, numbers.Length)];
 
     text.text = string.Format ("{0}{1}", a, b);        
     
 }

String Builder Format

Using cached StringBuilder improves the previous one a bit, it generates 86 Bytes per frame, the AppendFormat is generating garbage and then the set_Length() (used to clear the StringBuilder).

Test code:

 Text text;
 StringBuilder stringBuilder = new StringBuilder(20, 20);
 
 static readonly string[] numbers = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
 
 void Start () {
     text = GetComponent<Text> ();
     stringBuilder.Length = 3;
 }
 -j
 void Update () {
     string a = numbers[UnityEngine.Random.Range(0, numbers.Length)];
     string b = numbers[UnityEngine.Random.Range(0, numbers.Length)];
 
     stringBuilder.Length = 0;
     stringBuilder.AppendFormat ("{0}{1}", a, b);
 
     text.text = stringBuilder.ToString();
 }

Note: If I change the StringBuilder starting capacity and max capacity, the cost is the same but goes to ToString() method instead, but internally to the same method String.InternallyAllocateStr().

String Builder only Append

Instead of using StringBuilder.AppendFormat, change to use only String.Append. This reduces the cost to only 30 Bytes per frame (the same of the first one), the only cost here is the set_Length() which internally calls String.InternallyAllocateStr().

Test code:

 Text text;
 StringBuilder stringBuilder = new StringBuilder(20, 20);
 
 static readonly string[] numbers = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
 
 void Start () {
     text = GetComponent<Text> ();
     stringBuilder.Length = 3;
 }
 
 void Update () {
     string a = numbers[UnityEngine.Random.Range(0, numbers.Length)];
     string b = numbers[UnityEngine.Random.Range(0, numbers.Length)];
 
     stringBuilder.Length = 0;
     stringBuilder.Append (a);
     stringBuilder.Append (b);
 
     text.text = stringBuilder.ToString();
 }

Note: Does the same behaviour if I change starting and max capacity, the cost is the same but is on ToString() instead of set_Length().

String Builder by replacing chars

If instead of Append I replace chars directly by using [] and avoid the set_Length(), the cost is the same, 30 Bytes per frame, since the String.InternallyAllocateStr() goes to set_Chars().

Test code:

 Text text;
 StringBuilder stringBuilder = new StringBuilder(20, 20);
 
 static readonly char[] numbers = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
 
 void Start () {
     text = GetComponent<Text> ();
     stringBuilder.Length = 3;
 }

 void Update () {
     char a = numbers[UnityEngine.Random.Range(0, numbers.Length)];
     char b = numbers[UnityEngine.Random.Range(0, numbers.Length)];
 
     stringBuilder [0] = a;
     stringBuilder [1] = b;
 
     text.text = stringBuilder.ToString();
 }

Note: Again, does the same behaviour if I change starting and max capacity, instead of set_Chars(), the cost is in ToString() method.

String Builder, access internal string by reflection

There is a suggestion at in this post to access by refleciton to _str field from StringBuilder class to avoid the cost of ToString() method.

Test code:

 Text text;
 StringBuilder stringBuilder = new StringBuilder(20, 20);

 static System.Reflection.FieldInfo _sb_str_info = 
        typeof(StringBuilder).GetField("_str", 
        System.Reflection.BindingFlags.NonPublic | 
        System.Reflection.BindingFlags.Instance);
 
 static readonly char[] numbers = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
 
 void Start () {
     stringBuilder.Length = 3;
 
     text = GetComponent<Text> ();
 }
 
 void Update () {
     stringBuilder[0] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
     stringBuilder[1] = numbers[UnityEngine.Random.Range(0, numbers.Length)];
     stringBuilder[2] = (char) 0;
 
     var internalValue = _sb_str_info.GetValue (stringBuilder) as string;
     text.text = internalValue;
 }

In this case, there is no garbage at all. However, I see no change in the UI Text even though the editor shows the text field value is changing, like it is not being redrawn in screen. I suppose that could be because the string pointer is not changing and by taking a look at the Text code from the Unity UI it is comparing with != instead of Equals... not sure here.

 public virtual string text
 {
     get
     {
         return m_Text;
     }
     set
     {
         if (String.IsNullOrEmpty(value))
         {
             if (String.IsNullOrEmpty(m_Text))
                 return;
             m_Text = "";
             SetVerticesDirty();
         }
         else if (m_Text != value)
         {
             m_Text = value;
             SetVerticesDirty();
             SetLayoutDirty();
         }
     }
 }

I tried by forcing layout and vertices dirty after updating internal string, just in case, but had no luck (sad face).

Caching strings

Another option suggested in this blog post is to precache strings for different numbers but that is only reasonable for a small amount of digits. I like it because it is simple and could be generated at runtime, and works well for debug numbers like FPS where the number is normally between 0 and 60.

I tried it and it works really well and generates 0 Bytes per frame.

Test code:

 Text text;
 
 string[] generated;
 
 // Use this for initialization
 void Start () {
     text = GetComponent<Text> ();
 
     generated = new string[100];
 
     // should go from 0 to 99.
     for (int i = 0; i < 100; i++) {
         generated [i] = string.Format ("{0:00}", i);
     }
 }
 
 // Update is called once per frame
 void Update () {
     int random = UnityEngine.Random.Range (0, generated.Length);
     text.text = generated [random];
 }
 

Rendering numbers directly

One possible way to avoid all this garbage (I mean both the code and the unused memory) is to not use strings at all but to just render to the screen images for each number digit, where each digit is a different sprite.

When making TinyWarriors prototype I did a basic number rendering where I could specify the number of digits and it just created multiple Unity UI Images inside a horizontal layout.

Shows a test using images for each digit instead of a text.

Test code:

 public Image[] numbers;
 
 // in order, like 0, 1, 2, ..., 9
 public Sprite[] numberSprites;
 
 public bool fillZero = true;
 
 void Start()
 {
     SetNumber (0);
 }
 
 public void SetNumber(int number)
 {
     int tens = (number % 100) / 10;
     int ones = (number % 10);
 
     var tensActive = fillZero || tens != 0;
     var onesActive = fillZero || number > 0;
 
     numbers [0].gameObject.SetActive (tensActive);
     numbers [1].gameObject.SetActive (onesActive);
 
     if (tensActive)
         numbers [0].sprite = numberSprites [tens];
 
     if (onesActive)
         numbers [1].sprite = numberSprites [ones];
 }
 
 public void Update()
 {
     int random = UnityEngine.Random.Range (0, 100);
     SetNumber (random);
 }

The code could be adapted to support more digits. When profiling it in editor there is a lot of garbage generation, around 1KB per frame, in Canvas.SendWillRendereCanvases() because it is forcing a material rebuild each time a sprite is changed. However, I tested it on devices and it doesn’t so it must be something related with the Unity editor.

Other strategies

Other strategies include minimizing the garbage generation by reducing the text update frequency, for example, by avoiding updating the text if the number didn't change and/or updating the text from time to time and not every frame.

Conclusion

Since I just wanted a solution for a framerate counter (and other debug numbers) the last solutions are perfect and I believe those could even be extrapolated for other game needs, like showing the player points in an arcade game, with a bit of extra thinking.

References

Here is a list of some articles, forum and blog posts I took a look during the tests and the post writing.

Unity memory optimizations article - https://unity3d.com/es/learn/tutorials/temas/performance-optimization/optimizing-garbage-collection-unity-games

Memory management reference - http://www.memorymanagement.org/

FPS implementation caching strings - http://catlikecoding.com/unity/tutorials/frames-per-second/

Using reflection to set StringBuilder string to avoid garbage - http://www.defectivestudios.com/devblog/garbage-free-string-unity/

FPS Asset - http://blog.codestage.ru/unity-plugins/fps/

Another FPS Asset - https://www.assetstore.unity3d.com/en/#!/content/6513

StringBuilder API - https://msdn.microsoft.com/en-us/library/system.text.stringbuilder(v=vs.110).aspx

Performance tips for Unity for mobile - https://divillysausages.com/2016/01/21/performance-tips-for-unity-2d-mobile/

Unity UI Source code - https://bitbucket.org/Unity-Technologies/ui

Untiy Community Library - https://github.com/UnityCommunity/UnityLibrary

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