A flat, convex polygon in the world, and how it is painted.

%Cauldron3D.Polygon{
  points: [{0.0, 0.0, 0.0}, {64.0, 0.0, 0.0}, {64.0, 0.0, 64.0}],
  uvs: [{0.0, 0.0}, {64.0, 0.0}, {64.0, 64.0}],
  paint: {:texture, texture, 128}
}

uvs give each point's place on the paint, in its pixels; lights each point's light, 0 to 255 with 128 as the picture's own colours, carried across the polygon for {:shaded, texture}. cull drops the polygon when its points run that way round on the screen: :clockwise, :counter_clockwise, or :none to keep both faces.

In a picture drawn in full colour, tints gives each point a {r, g, b, a} that its paint's colour and alpha are multiplied by (1.0 leaves them as they are), carried across the polygon with the perspective; blend mixes the polygon with what is behind it: {:alpha, amount} lays it over at amount (0.0 to 1.0) times its alpha, {:add, amount} adds amount times its alpha of its colour to what is there, {:premultiplied, amount} adds amount of its colour (already multiplied by its alpha) to what is there kept at one minus amount times its alpha, and {:darken, amount} multiplies what is there by one minus amount of its colour.

A polygon with a clear colour is see-through where its paint is that colour, and one with an alpha_test (0.0 to 1.0) where its paint's own alpha is below it; an unblended polygon that is see-through in places still hides what is behind it where it is not. depth: :always draws it over everything whatever its distance; depth: :near_third keeps its depth in the nearest third of the depth range, so that it is in front of everything else but what lies within half the near distance beyond the near plane, and is still in front or behind among its own kind.

Blended, see-through and always-on-top polygons are drawn after the others, the unblended first, then the blended in the order given.

The paints are those Cauldron3D.Paint draws.