Imagine we have a triangle ABC with normals a, b, c.
glShadeModel is set to GL_SMOOTH.
The question is:
from OpenGL point of view, what is the normal to a point p inside a triangle?
Why do I need this:
I slice a triangle in two, but I want the picture to look exactly the same way as before slicing. This extra tesselation is required for sophisticated coloring, we develop 3D graphs plotter. =)