A rectangle of a texture placed in a CauldronGPU.SpriteLayer.

• texture — the handle of a texture or canvas
• source — {x, y, width, height} in the texture's pixels, the part drawn; nil (the default) draws the whole texture
• position — {x, y} in the layer's view, where the sprite's origin lands
• origin — {x, y} in the source's pixels, the point placed at position and turned about; default {0, 0}
• scale — {x, y}; negative mirrors, zero draws nothing; default {1, 1}
• angle — degrees, counter-clockwise as seen; exact at whole quarter turns
• colour — {r, g, b} from 0 to 1, multiplied into the texture's colours
• alpha — 0 to 1, multiplied into the texture's alpha
• mode — :over (the default), :add or :subtract

Colours are display values: they are blended as stored, with no conversion to linear light. A pixel is drawn when its centre lies inside the turned and scaled rectangle; it takes the texture's sample at that point, by the texture's own filter.

:over lays the colour over what is there by its alpha. :add adds the colour times its alpha, each channel at most 1, and adds the alpha. :subtract multiplies each channel by one less the colour times its alpha, keeping the alpha.