GL_BLEND vs gl_TexEnv(...gl_MODULATE)

OpenGL OpenGL: Basic Coding
1

Is it possible to use gl_TexEnv(…gl_MODULATE) instead of using alpha blending, when I make a second pass for my spheremap ? Is it better in term of performance ?

2

I believe the answer is no. Something to do with glTexEnv only working from input from the primary/secondary color, and outputs of previous texture units. It does not modulate with the frame buffer.

You need to blend modes for that.

Nutty

3

Thanks.

4

possibly you have multitexture_arb supported with 2 textures, then you can boost it up by doing just one pass…

glActiveTextureARB( GL_TEXTURE0_ARB );
glBind texture from first pass…
glActiveTextureARB( GL_TEXTURE1_ARB );
glBind second one and enable spheremapping here in
glTexEnv GL_MODULATE
glActiveTextureARB( GL_TEXTURE0_ARB );
just set back to the first stage…