For some reason, only the first texture unit is referenced by my samplers. For setting the samplers, I do this after having created, compiled, and linked the shader program:
int unit0Loc, unit1Loc;
unit0Loc = glGetUniformLocationARB(program, "unit0");
unit1Loc = glGetUniformLocationARB(program, "unit1");
glUniform1iARB(unit0Loc, 0);
glUniform1iARB(unit1Loc, 1);
For specifying the textures for each unit in the program, I use this:
int maxUnits = TextureManager::getMaxTextureUnits();
for(register int i=0; i<maxUnits; ++i) {
glActiveTextureARB(GL_TEXTURE0_ARB + i);
glBindTexture(GL_TEXTURE_2D, textures);
printf("Texture '%i' bound to unit '%i'\n", textures, i);
}
For drawing the primitive I use this:
glBegin(GL_POLYGON);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0, 0); glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0, 0); glVertex2f(-1, -1);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1, 0); glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1, 0); glVertex2f(1, -1);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1, 1); glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1, 1); glVertex2f(1, 1);
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0, 1); glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0, 1); glVertex2f(-1, 1);
glEnd();
And, finally, in the vertex shader I use:
void main(void)
{
gl_TexCoord[0] = gl_MultiTexCoord0;
gl_TexCoord[1] = gl_MultiTexCoord1;
gl_Position = ftransform();
}
And in the fragment shader:
uniform sampler2D unit0, unit1;
void main(void)
{
gl_FragColor = texture2D(unit0, gl_TexCoord[0].st) * texture2D(unit1, gl_TexCoord[1].st);
}
