I need to render a scene in an FBO : (some 2D image with alpha blending mode [glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA)]
this FBO is rendered and blended with the same blending mode with other images....
if I draw in my FBO some image with glcolor4f(1,1,1,0.5); when the fbo is rendered it seeems that the the image is not at half the luminance, but 1/4 of the luminance.... it seems that RGB value are premultiplied by alpha. Is it normal ?
what can I do ? Is it a bug ?