Sprites drawn in order into a target, one layer of a {:layers, [layer]} change.

• target — :frame (the default), the window's picture, or a canvas handle
• clear — {r, g, b, a} from 0 to 1 the target is filled with first; nil (the default) draws over what the target holds
• port — {x, y, width, height} in the target's pixels; the sprites are drawn only inside it. nil (the default) is the whole target
• view — {x, y, width, height}, the part of the sprites' space shown in the port, stretched to fill it. nil (the default) places sprites in pixels from the port's top-left corner
• sprites — CauldronGPU.Sprites, drawn first to last

The frame's layers are drawn over the 3D scene, a transparent picture laid over its display colours. A renderer that has never been sent a CauldronGPU.Camera draws its layers alone, on black, and skips the 3D passes.

%CauldronGPU.SpriteLayer{
  clear: {0.0, 0.0, 0.0, 1.0},
  view: {0, 0, 320, 200},
  sprites: [%CauldronGPU.Sprite{texture: ship, position: {160, 100}, origin: {8, 8}}]
}