Is there any way to keep the transparent parts of a sprite from
drawing in the depth buffer? I've got a field of sprites arranged
across the x-z plane and want to put another sprite in the middle
of the field, but it gets clipped by the transparent parts of the
sprites in front of it. Worst case, I can ditch the depth buffer
and draw everything in order, but that's not as convenient..
I don't think there's any solution to that problem as GL alpha-test
is not exposed in Quartz Composer. Usually, (simple) transparency in
GL can be handled by drawing opaque objects first with z-buffer in
read-write mode, then transparent objects with z-buffer in read-only
mode
Also, are billboards supposed to be independent of the current 3d
transformation? As I recall, billboards in OpenGL act just like
quads but "face forward", but as far as I can tell the only way to
position a QC billboard is in its properties--i.e., no z position.
Is that correct?
