Alpha blending issue

BlitzMax Forums/OpenGL Module/Alpha blending issue

_JIM	(Posted 2010) [#1]

Hi,

I'm having a little problem with alpha blending on a FBO.
I'll post some code later, but the here's the problem:

I direct the drawing to an FBO.
I draw a large quad (background) on the FBO.
I draw a smaller quad with glColor4f(1,1,1,0.5) on top of that.

I assign the FBO to an object and render it.

It seems that the secon quad "punches a hole" through the background, and by that I mean that it writes to the destination alpha chanel.

I'm using glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)

Any ideas on how to fix this?

_JIM	(Posted 2010) [#2]

Heh, looks like this fixed it:

glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_COLOR)