Hi Im wondering if anyone could give me any tips on what shadow techniques would be recommended in a game with a large world, for example a car racing game taking place in a big city. I can assume that the game is played on the newest graphics hardware avalible. Im willing to sacrifice some visuell apperance for performance The technique must be implementable in OpenGL I really appreciate any imputs Pål- Arve Nilsen

You could take a look at stencil volume shadows and shadow maps. There are a lot of examples on the internet for both techniques.

The first one extrudes object edges (as seen from the light) and uses these volumes and the stencil buffer to determine which pixels are lit and which are not.

With shadow maps you draw the depth of the scene as seen from the light to a texture and use it check wether a fragment on a polygon is lit or not. There are other methods.

The advantage of volume shadows is that you don't need to render extra textures and it's easy to use for spot lights and omni directional lights (point lights), omnidirectional shadow maps are possible but it requires rendering more depth textures.

I dont have much experience with shadow maps myself so someone else will have to tell you the advantages of it.