OPenGL related. 2007-6-5(Tue)

``There is a bit strange small road start with the station. It is parallel to the main street and almost tangential direction, but not normal.'' ... Robert explained how to reach his home.

• glRotate()'s angle is degree!
• One of the OpenGL's common pitfall is command order mistake. I write a scenegraph node to manipulate color material. But I wrote it as:

       glEnable(GL_COLOR_MATERIAL);
       glColorMaterial(GL_FRONT, GL_DIFFUSE);
       glColor4fv(base_color);
       

  But in this way, always next object is affected. Because glColorMaterial sets the material color from the current color. Therefore, the following code is correct.

       glColor4fv(base_color);  // set the current color first.
       glEnable(GL_COLOR_MATERIAL);
       glColorMaterial(GL_FRONT, GL_DIFFUSE); // use current color