Question

I want to write a GLSL Fragment Shader that can do texture mapping and vertex coloring. Is it possible to do both in the one shader?

At the moment, I can do this:

gl_FragColor = texture2D(tex, gl_TexCoord[0].st);

Which causes textured verts to be drawn, but not colored verts.
(which looks like this: http://www.tiikoni.com/tis/view/?id=124eb69)

I can also do this:

gl_FragColor = gl_Color;

Which causes colored verts to be drawn but not textured verts.
(Which looks like this: http://www.tiikoni.com/tis/view/?id=5bcd838)

If I do this:

gl_FragColor = texture2D(tex, gl_TexCoord[0].st) * gl_Color; (which looks like the first code snippet)

Only textured verts get drawn… which is my problem.

Answer 1

What I expect to see is the textured and non-textured verts to all show up, in the last code snippet.

You shouldn’t expect that.

There’s no such thing as a “textured vert” or a “non-textured vert”. There is only a color, whatever that color may be. That’s the whole point of shaders: to use arbitrary code to compute a color however you want.

You are computing the color by multiplying the result of a texture fetch with a per-vertex interpolated color. The result will be a combination of the two colors. Namely, the product of them. Therefore, the resultant color will look somewhat like the original texture.