frustum culling

The Opengl standard culling affect on vertices and no on single triangle?
But in game programming this is too cost,
and it’s for this reason that use algorithm
as pvs, bsp and so on?


To put it precisely, OpenGL does not do any frustum culling. It can only cull backfaces (or frontfaces). OpenGL does clip the polygons to the frustum however. That’s why it is imperative you implement your own frustum culling. OpenGL will happily transform and then clip any primitives that lie outside the frustum. You need to cull those primitives, so that OpenGL doesn’t waste any time dealing with primitives that you know are unseen.