I’m writing a basic planet viewer OpenGL application, just for fun. I have the basics working, with the glorious planet, implemented through a gluSphere(), rotating with the classic earth texture map applied.
Now, what if I want to apply a second texture map through OpenGL (say, the “earth clouds”)?
The earth texture is a color image and the cloud texture is a grey-level image. I want the final result to be like cloud floating above the earth.
I tried use different texture environment, but the earth texture is always hidden by the cloud. Which environment parameter should I choose?