Shadows from multiple light sources (DX11)

Question

I'm currently trying to extend my current basic shadow mapping system to allow objects to have shadows cast from multiple lights. At the moment I have generated both shadow maps correctly but the problem is getting them both to be rendered on the scene.

My draw function currently goes like this:

for (int iLight = 0; iLight < mNumLights; iLight++)
{
    mShadowMap[iLight]->SetNullRenderTarget(md3dImmediateContext);

    DrawSceneToShadowMap(iLight);

    RestoreRenderTarget();

    SetShadowMap(iLight);
    SetShadowTransform(iLight);

    DrawScene();

}

mSwapChain->Present(0, 0)

Only the second shadow map is used and drawn, what am I missing here?

Answer 1

The two standard ways of combining shadow maps in a forward renderer are either to do multi-pass lighting with additive blending where each pass adds in the light contribution from a different light or single-pass lighting where the shader loops over lights in the scenes and accumulates their light contributions. MIN blending isn't really the right way to combine contributions from multiple lights in a multi-pass lighting approach. I'd suggest trying additive blending instead.