VBGamer

hi, could someone tell me how I can quickly reject geometry based on the projection matrix/clip planes? As in, I have a tile (of 4 vertices), how can I write a function CheckVisibility() that returns true if it'll be partly/completely on screen or false if it's not... In Dx7 we had ComputeSphereVisibility and stuff, but I cant find a way of getting the frustum clipping planes or any D3DX function to check visibility for me.... plz help, my Graphics engine is hugely inefficient without it :( Jack;