How to implement a "render-to-texture" pipeline in Direct3D 11?

Question

I am trying to some GPGPU calculations using HLSL and Direct3D 11. My goal is to calculate several images sequentially (one rendering per image), then sum them.

To achive this I created three textures: one is an input, two are for summarizing the results. The method I am trying: first I render to texture2 (and I use the texture and texture3 textures as input), then I render to texture3 with a slightly modified pixel shader (and I use the texture and texture2 textures as input). After this, I dump the textures to a PNG file. My problem is that somehow the second pixel shader doesn't get the result of the first shader (texture2), but the original, empty texture. I defined both texture, texture2, and texture3 with usage D3D11_USAGE_DEFAULT, and D3D11_BIND_RENDER_TARGET | D3D11_BIND_SHADER_RESOURCE binding flags.

My HLSL shader (shader1):

float4 main(PS_INPUT input) : SV_TARGET
{
...
float4 val5 = 0.25F * (val + val2 + val3 + val4) + tex3.Sample(sam, input.Tex4);
return val5;
}

The other shader (shader2):

float4 main(PS_INPUT input) : SV_TARGET
{
...
float4 val5 = 0.25F * (val + val2 + val3 + val4) + tex2.Sample(sam, input.Tex4);
return val5;
}

The code that performns the rendering and the dumping of textures:

context->OMSetRenderTargets(1, &targetViewTexture2, NULL);

float z = 280.0F;
GenMatrix(z);
context->VSSetShader(vs, NULL, 0);
context->PSSetShader(ps, NULL, 0);
context->PSSetSamplers(0, 1, &state);
context->VSSetConstantBuffers(0, 1, &cbuf);
context->Draw(6, 0);
swapChain->Present(0, 0);

context->OMSetRenderTargets(1, &targetViewTexture3, NULL);
z = 0.0F;
GenMatrix(z);
context->VSSetShader(vs, NULL, 0);
context->PSSetShader(ps2, NULL, 0);
context->PSSetSamplers(0, 1, &state);
context->VSSetConstantBuffers(0, 1, &cbuf);
context->Draw(6, 0);
swapChain->Present(0, 0);
DirectX::ScratchImage im;
DirectX::CaptureTexture(device, context, texture3, im);
const DirectX::Image *realImage = im.GetImage(0, 0, 0);
HRESULT hr2 = DirectX::SaveToWICFile(*realImage, DirectX::WIC_FLAGS_NONE, GUID_ContainerFormatPng, L"output_tex3.png", NULL);
DirectX::CaptureTexture(device, context, texture2, im);
realImage = im.GetImage(0, 0, 0);
hr2 = DirectX::SaveToWICFile(*realImage, DirectX::WIC_FLAGS_NONE, GUID_ContainerFormatPng, L"output_tex2.png", NULL);

The ouput of the first pass (ps) is correct, but the second is not. If I only leave the shader code:

    float4 val5 = tex2.Sample(sam, input.Tex4);

I get an empty image. Am I missing something? Do I have to call some methods to use the texture in the second pixel shader? I think I pinpointed the relevant sections of my large code base, but if you need more information just ask for it in the comment section.

Are you using Visual Studio 2012? Because it has very powerful Graphics debugging Tools. — Cédric Bignon
I had swapChain->Present before, because I used the screen to look at the result of each step (I commented it out now). I use VS2012 but I don't know how to start; as the texture seems to be filled after the first Draw call, but seems to be empty in the second. — WebMonster
Have you tried to use the Visual Studio 2012 Graphics debugging Tools? In Debug->Graphics->Start Diagnostics. — Cédric Bignon
I've got an interesting result: using the debugging tools you mentioned I looked at the input texture and it is in fact not empty, but contains the correct value. The output might be incorrect because of other problem. — WebMonster

WebMonster WebMonster · Accepted Answer · 2013-07-30T15:34:33

The problem was that I used the texture both as input and output. You could use a texture either as input or render target in one pass.

How to implement a "render-to-texture" pipeline in Direct3D 11?

1 Answers