The canvas_item shader docs mention the built-in
POINT_COORD for both the
fragment and the
light processor function. The descriptions in the docs are:
in vec2 POINT_COORD Coordinate for drawing points.
in vec2 POINT_COORD UV for Point Sprite.
I don't get what is the purpose of this variable. I've done quite some experiments to find out what it could be doing, but it looks like the values are always zero.
What is the meaning of this variable? Are there any examples of how to make use of it?
What I have found out so far:
This question suggests that it has something to do with "point sprites" (which I can't find any documentation for either) and with the
POINT_SIZE built-in for the
vertex processor function (which I tried to set, but also no effect). The example of this related GitHub issue is unfortunately missing some files so that I could learn from it either.