Rendering multiple overlapping non-opaque textures to a framebuffer

Question

I'm trying to render a set of textured geometry to a single FBO, and then render that FBO to the scene. The problem is that overlapping semi-transparent areas of that geometry are not rendered correctly. They end up too opaque and dark. If I render the geometry directly to the scene it renders correctly, but I need to render it first to the FBO.

By the way, I'm using the following for blending (according to opengl - blending with previous contents of framebuffer):

• rendering geometry to the FBO: glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE)
• rendering the FBO to the scene: glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA)

I'm doing this for OpenGL ES 2.0.

Answer 1

Actually, I found that the problem was the blending function used to render the geometry to the FBO.

Instead of:

glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE)

I have to use:

glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA)

And now it works as good as if I was rendering the geometry directly to the scene.