Hi,

I want to expand maximum lights capability in my 3D engine. The DX9, forward rendering is used there. The lights pass to shader as array of corresponding shader structs, located in registers memory. So, registers memory is restriction for max lights.

Could anybody tell me tell whether the performance will be good enough when i will hold lights array in Volume Texture? I mean in compare to registers memory..

Thanks for your help!

I think that the bandwidth usage and overhead of transferring a few kilobytes to the GPU is no problem. You can use Vertex Texture Fetch in the vertex shader to lookup your lights array.

Only when you want each light to cast shadows will you notice performance issues.

thank you for reply, Tispe.

Only direct lighting calculations are there..

It might also be good to define what you mean with 'many lights'. Does this mean many lights in total in the scene, or many lights affecting a single renderable?

If it's the first, you could optimize by having relative small renderables ('submeshes') and then take for example the 8 lights that most affect that renderable. In most situations having more then 8 lights affecting one renderable, the difference in result is quite small.

With Vertex texture fetch, one can render the same mesh using instancing.

As for D3D9, I think it's for people with new graphic card but stuck with Windows XP.

One can also fall back to Doom3 style rendering,which use additive blending with multiple pass.