when to use flat or smooth shading ???

i have a question …
when i have a mesh that has smooth surface and edge and flat surface together , how do i render the mesh so that only the smooth surface will appears smooth and not the flat surface ???

Hi !

You have to split up the rendering into multiple glBegin/glEnd block one for flat and one for smooth, then you can change between flat/smooth any where you want as long as you are not inside a glBegin/glEnd block.