Drawing Sprites with Artemis

Question

I am trying to trace the StarWarrior code (the Artemis tutorial). I cannot figure out how these sprites are being drawn. This is the code where the player's ship is initialized:

/// <summary>The initialize player ship.</summary>
private void InitializePlayerShip()
{
    Entity entity = this.entityWorld.CreateEntity();
    entity.Group = "SHIPS";

    entity.AddComponentFromPool<TransformComponent>();
    entity.AddComponent(new SpatialFormComponent("PlayerShip"));
    entity.AddComponent(new HealthComponent(30));

    entity.GetComponent<TransformComponent>().X = this.GraphicsDevice.Viewport.Width * 0.5f;
    entity.GetComponent<TransformComponent>().Y = this.GraphicsDevice.Viewport.Height - 50;
    entity.Tag = "PLAYER";
}

Which line of code actually leads to the ship being drawn? The drawing takes place in PlayerShip.cs. Here is a commented version of the code with what I think is happening:

/// <summary>The initialize player ship.</summary>
private void InitializePlayerShip()
{
    Entity entity = this.entityWorld.CreateEntity(); //declare and initialize entity
    entity.Group = "SHIPS"; //Unused label

    entity.AddComponentFromPool<TransformComponent>(); //Add the component to store X and Y
    entity.AddComponent(new SpatialFormComponent("PlayerShip")); //Add a component which is just a String (perhaps this has something to do with PlayerShip.cs?)
    entity.AddComponent(new HealthComponent(30)); //Add a health component with 30 hp

    entity.GetComponent<TransformComponent>().X = this.GraphicsDevice.Viewport.Width * 0.5f; //Initialize the TransformComponent's X
    entity.GetComponent<TransformComponent>().Y = this.GraphicsDevice.Viewport.Height - 50; //Initialize the TransformComponent's Y
    entity.Tag = "PLAYER"; //Unused label
}

So how is the actual sprite being drawn? Because, I am not seeing it. :(

If it is being drawn by entityWorld.Draw() in the Draw() method, then which line(s) of code put it in the world to be drawn? Or what is actually happening in entityWorld.Draw()?

I believe the RenderSystem is the one that is doing the drawing, but I don't get how it is being called.

I am sorry for the uninformed question, but I have made no progress after about 12 hours, and I desperately need some guidance!

Answer 1

Each system in Artemis has a function called process, the process function in the RenderSystem looks like this:

@Override
protected void process(Entity e) {
    Spatial spatial = spatials.get(e.getId());
    Transform transform = transformMapper.get(e);

    if (transform.getX() >= 0 && transform.getY() >= 0 && transform.getX() < container.getWidth() && transform.getY() < container.getHeight() && spatial != null) {
        spatial.render(graphics);
    }
}

This is getting the Spatial component from each entity. The Spatial component defines the sprite to be rendered.

That sprite is then being drawn to screen with the render call you see above. Which looks like this:

@Override
public void render(Graphics g) {
    g.setColor(Color.green);
    g.setAntiAlias(true);
    ship.setLocation(transform.getX(), transform.getY());
    g.fill(ship);
}