Mixing colors with standard openGL

OpenGL OpenGL: Basic Coding
1

Hi,

I want to put a texture with BLEND mode on an object, so that the color can be seen through. I already did this, but I would like to set the strength of the effect. This is my initialisation code:

  glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_BLEND);
  GLfloat c[4] = {1.0, 1.0, 1.0, 0.0};
  glTexEnvfv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, c);
  glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
  glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
  glEnable(GL_TEXTURE_GEN_S);
  glEnable(GL_TEXTURE_GEN_T);

  glBindTexture(GL_TEXTURE_2D, texNrMetalImg);
  glEnable(GL_TEXTURE_2D);

I would like to mix the colors like e.g. 20% reflection and 80% base color of the faces. Is this possible without extensions?

Thanks,

Kilam.

2

glTexEnvi(GL_TEXTURE_2D, GL_TEXTURE_ENV_MODE, GL_COMBINE);
glTexEnvi(GL_TEXTURE_2D, GL_SOURCE0, GL_TEXTURE);
glTexEnvi(GL_TEXTURE_2D, GL_SOURCE1, GL_PRIMARY_COLOR);
glTexEnvi(GL_TEXTURE_2D, GL_SOURCE2, GL_CONSTANT);
glTexEnvi(GL_TEXTURE_2D, GL_COMBINE_RGB, GL_INTERPOLATE);

You can now use the constant color to control the amount of base color and reflection texture. If constant color is 1.0, you have 100% reflection texture, and if it’s 0.0, you have 100% base color.

3

Bob,

GL_COMBINE is unknown on my system. Do you have a newer OpenGL? I only know GL_COMBINE_EXT, but I don’t want to use extensions if I don’t have to.

Kilam.

4

GL_COMBINE_EXT is from the extension EXT_texture_env_combine, which is a part of the standard since OpenGL 1.3. When it became standard, the EXT-suffix was removed. Get the latest glext.h from here for the missing constants.