I have a 3D Model which is built up from quad elements. OGL makes with the depth buffer a culling of hidden faces. Can i speed up with my own hidden surface method and how?
Well, first of all you can try and sort your faces front to back, as that will not rasterize most of the fragments (because the depth test fails).
Then, if you don’t always see everything of your model (for example, it’s a house and you can walk through it), you could use BSP trees, octrees or other space partitioning algorithms and cull away most of the unseen geometry before even sending it to the graphics card. There’s heaps of info on the web on these algorithms.
Hidden surface removal, back face culling and frustum culling are 3 (quite) different tasks.
Back face culling it’s easily done by calculating the angle between the face normal and the camera view direction.