Thank u for your help, mhagain.

By saying "it can't read the pixels correctly", I mean it gets zero for all the pixel value in the MFC program, which is not supposed. While in the glut based...

I am using to use glReadPixels() in Visual Studio. It works fine in the project which uses glut window, but in another project which uses MFC to display, it can't read the pixels correctly. Anyone...

I will appreciate it a lot if anyone could help me to understand the function build_object() below about glColor3ub, I have no idea how does glColor3ub work, especially about the bit operation, like ...