This may be something well known, but I'm just now bumping into it. I've searched the reference and forum however, and am not seeing it. Will happily delete the question if it's a duplicate.

Why does P3D not allow for an alpha channel when using point()? Or is it supposed to, but doesn't on some systems? Is it a Processing thing, or a hardware thing, or what?

All other modes work as expected. Test code below confirms P3D shows a black point over the white one, when it should be invisible (as it indeed is in all other modes).

1. import processing.opengl.*;
2. //size(100, 100);
3. //size(100, 100, JAVA2D);
4. //size(100, 100, P2D);
5. size(100, 100, P3D);
6. //size(100, 100, OPENGL);
7. stroke(255);
8. point(width/2, height/2);
9. stroke(0, 0);
10. point(width/2, height/2);