Question

I am trying to implement deferred shading using MRTs. For that, I need to accumulate the color and the normals in two rendering targets. I defined two R32G32B32A32 textures for that end.

The pixel buffer outputs to both rendering targets. However, how do I instruct it to accumulate the values, rather than replace or blend them?

I tried defining the following blending state:

blendState.RenderTarget[0].BlendEnable =            TRUE;
blendState.RenderTarget[0].RenderTargetWriteMask =  D3D11_COLOR_WRITE_ENABLE_ALL;
blendState.RenderTarget[0].SrcBlend =               D3D11_BLEND_ONE;
blendState.RenderTarget[0].DestBlend =              D3D11_BLEND_ONE;
blendState.RenderTarget[0].BlendOp =                D3D11_BLEND_OP_ADD;
blendState.RenderTarget[0].SrcBlendAlpha =          D3D11_BLEND_ONE;
blendState.RenderTarget[0].DestBlendAlpha =         D3D11_BLEND_ONE;
blendState.RenderTarget[0].BlendOpAlpha =           D3D11_BLEND_OP_ADD;
blendState.RenderTarget[1].BlendEnable =            TRUE;
blendState.RenderTarget[1].RenderTargetWriteMask =  D3D11_COLOR_WRITE_ENABLE_ALL;
blendState.RenderTarget[1].SrcBlend =               D3D11_BLEND_ONE;
blendState.RenderTarget[1].DestBlend =              D3D11_BLEND_ONE;
blendState.RenderTarget[1].BlendOp =                D3D11_BLEND_OP_ADD;
blendState.RenderTarget[1].SrcBlendAlpha =          D3D11_BLEND_ONE;
blendState.RenderTarget[1].DestBlendAlpha =         D3D11_BLEND_ONE;
blendState.RenderTarget[1].BlendOpAlpha =           D3D11_BLEND_OP_ADD;

But the values I’m getting are weird.

Please help! How do I accumulate values?

Answer 1

To implement deferred shading you technically should not accumulate either normals or color, since when you will do the deferred processing (light calculations/occlusion/depth of field…), each MRT texture pixel(color/depth/normals), need to represent the closest object from the view point.

So only setting a depth state to read/write and comparison function to either less/lessequal, with no blend at all should be the way to go.