Mix multisample and non multisample rendering in Directx11

Question

is there a way to mix multisample and non multisample rendering in Directx11? It seems that when I create a multisampled render target I always get a multisampled rendering, regardless of the value of the MultisampleEnabled flag of the RasterizerDescription.

Microsoft says:

"To use multisampling, set the enable field in the rasterization description, create a multisampled render target, and either read the render target with a shader to resolve the samples into a single pixel color or call ID3D11DeviceContext::ResolveSubresource to resolve the samples using the video card."

and also

"There are no restrictions for mixing multisampled and non-multisampled rendering within a single render target."

But then in the rasterizer description page it says:

" For feature levels 10.1 and higher, the setting of MultisampleEnable has no effect on points and triangles with regard to MSAA and impacts only the selection of the line-rendering algorithm as shown in this table...

"

So, how can I temporarily turn multisampling off on a multisampled render target, in order to draw part of the scene without multisampling?

Answer 1

As far as I know you cant.

You will have to create another render target without MSAA and do one of two things:

• Copy the MSAA target into the non-MSAA, resolving the subsamples, and keep rendering in the non-MSAA for your alpha geometry (wild guess that this is why you need MSAA off)
• Render non-MSAA to the non-MSAA target and merge the two render targets, that only works for opaque passes unless you use depth peeling (http://en.wikipedia.org/wiki/Depth_peeling).

In theory you could use the pixel shader and render a 1-pixel larger triangle and kill pixels outside of the intended triangle boundaries but in reality rounding errors will likely create a mess and discarding fragments in the shader has a small performance impact compared to non-discarding shaders on some hardware.

(If anyone knows a better solution that would be very much welcome.)