Loading Texture2D data in DirectX 11 Compute Shader - directx

Question

I am trying to read some data from a texture2d in DirectX11 compute shader, however, the 'Load' function of a texture2D object keeps returning 0 even though the texture object is filled with the same float number.
This is a 160 * 120 texture2d with DXGI_FORMAT_R32G32B32A32_FLOAT. The following code is how I created this resource:
HRESULT TestResources(ID3D11Device* pd3dDevice, ID3D11DeviceContext* pImmediateContext) {
float *test = new float[4 * 80 * 60 * 4]; // 80 * 60, 4 channels, 1 big texture contains 4 80 * 60 subimage
for (int i = 0; i < 4 * 80 * 60 * 4; i++) test[i] = 0.7f;
HRESULT hr = S_OK;
D3D11_TEXTURE2D_DESC RTtextureDesc;
ZeroMemory(&RTtextureDesc, sizeof(D3D11_TEXTURE2D_DESC));
RTtextureDesc.Width = 160;
RTtextureDesc.Height = 120;
RTtextureDesc.MipLevels = 1;
RTtextureDesc.ArraySize = 1;
RTtextureDesc.Format = DXGI_FORMAT_R32G32B32A32_FLOAT;
RTtextureDesc.SampleDesc.Count = 1;
RTtextureDesc.SampleDesc.Quality = 0;
RTtextureDesc.Usage = D3D11_USAGE_DYNAMIC;
RTtextureDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
RTtextureDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
RTtextureDesc.MiscFlags = 0;
D3D11_SUBRESOURCE_DATA InitData;
InitData.pSysMem = test;
InitData.SysMemPitch = sizeof(float) * 4;
V_RETURN(pd3dDevice->CreateTexture2D(&RTtextureDesc, &InitData, &m_pInputTex2Ds));
//V_RETURN(pd3dDevice->CreateTexture2D(&RTtextureDesc, NULL, &m_pInputTex2Ds));
D3D11_SHADER_RESOURCE_VIEW_DESC SRViewDesc;
ZeroMemory(&SRViewDesc, sizeof(SRViewDesc));
SRViewDesc.Format = RTtextureDesc.Format;
SRViewDesc.ViewDimension = D3D11_SRV_DIMENSION_TEXTURE2D;
SRViewDesc.Texture2D.MostDetailedMip = 0;
SRViewDesc.Texture2D.MipLevels = 1;
V_RETURN(pd3dDevice->CreateShaderResourceView(m_pInputTex2Ds, &SRViewDesc, &m_pInputTexSRV));
delete[] test;
return hr;
}
And then I try to run dispatch with X = Y = 2 and Z = 1 like the following:
void ComputeShaderReduction::ExecuteComputeShader(ID3D11DeviceContext* pd3dImmediateContext, UINT uInputNum, ID3D11UnorderedAccessView** ppUAVInputs, UINT X, UINT Y, UINT Z) {
pd3dImmediateContext->CSSetShader(m_pComputeShader, nullptr, 0);
pd3dImmediateContext->CSSetShaderResources(0, 1, &m_pInputTexSRV); // test code
pd3dImmediateContext->CSSetUnorderedAccessViews(0, uInputNum, ppUAVInputs, nullptr);
//pd3dImmediateContext->CSSetUnorderedAccessViews(0, 1, &m_pGPUOutUAVs, nullptr);
pd3dImmediateContext->UpdateSubresource(m_pConstBuf, 0, nullptr, &m_ConstBuf, 0, 0);
pd3dImmediateContext->CSSetConstantBuffers(0, 1, &m_pConstBuf);
pd3dImmediateContext->Dispatch(X, Y, Z);
pd3dImmediateContext->CSSetShader(nullptr, nullptr, 0);
ID3D11UnorderedAccessView* ppUAViewnullptr[1] = { nullptr };
pd3dImmediateContext->CSSetUnorderedAccessViews(0, 1, ppUAViewnullptr, nullptr);
ID3D11ShaderResourceView* ppSRVnullptr[1] = { nullptr };
pd3dImmediateContext->CSSetShaderResources(0, 1, ppSRVnullptr);
ID3D11Buffer* ppCBnullptr[1] = { nullptr };
pd3dImmediateContext->CSSetConstantBuffers(0, 1, ppCBnullptr);
}
And I wrote a very simple CS shader to try to get the data in the texture2d and out it. So, the compute shader looks like this:
#define subimg_dim_x 80
#define subimg_dim_y 60
Texture2D<float4> BufferIn : register(t0);
StructuredBuffer<float> Test: register(t1);
RWStructuredBuffer<float> BufferOut : register(u0);
groupshared float sdata[subimg_dim_x];
[numthreads(subimg_dim_x, 1, 1)]
void CSMain(uint3 DTid : SV_DispatchThreadID,
uint3 threadIdx : SV_GroupThreadID,
uint3 groupIdx : SV_GroupID) {
sdata[threadIdx.x] = 0.0;
GroupMemoryBarrierWithGroupSync();
if (threadIdx.x == 0) {
float4 num = BufferIn.Load(uint3(groupIdx.x, groupIdx.y, 1));
//BufferOut[groupIdx.y * 2 + groupIdx.x] = 2.0; //This one gives me 2.0 as output in the console
BufferOut[groupIdx.y * 2 + groupIdx.x] = num.x; //This one keeps giving me 0.0 and in the texture, r = g = b = a = 0.7 or x = y = z = w = 0.7, so it suppose to print 0.7 in the console.
}
GroupMemoryBarrierWithGroupSync();
}
I think the way I print the CS shader result on CPU end is correct.
void ComputeShaderReduction::CopyToCPUBuffer(ID3D11Device* pdevice, ID3D11DeviceContext* pd3dImmediateContext, ID3D11Buffer* pGPUOutBufs) {
D3D11_BUFFER_DESC desc;
ZeroMemory(&desc, sizeof(desc));
pGPUOutBufs->GetDesc(&desc);
desc.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
desc.Usage = D3D11_USAGE_STAGING;
desc.BindFlags = 0;
desc.MiscFlags = 0;
if (!m_pCPUOutBufs && SUCCEEDED(pdevice->CreateBuffer(&desc, nullptr, &m_pCPUOutBufs))) {
pd3dImmediateContext->CopyResource(m_pCPUOutBufs, pGPUOutBufs);
}
else pd3dImmediateContext->CopyResource(m_pCPUOutBufs, pGPUOutBufs);
D3D11_MAPPED_SUBRESOURCE MappedResource;
float *p;
pd3dImmediateContext->Map(m_pCPUOutBufs, 0, D3D11_MAP_READ, 0, &MappedResource);
p = (float*)MappedResource.pData;
for (int i = 0; i < 4; i++) printf("%d %f\n", i, p[i]);
pd3dImmediateContext->Unmap(m_pCPUOutBufs, 0);
printf("\n");
}
The buffer that bind to UAV has only 4 elements. So, if all the float numbers in my texture2d are 0.7, I should have 4 0.7s get printed in CopyToCPUBuffer function instead of 0.0s.
Is anyone know what could be wrong in my code or can someone provide me an entire example or a tutorial that shows how to read DirectX 11 texture2d's data in compute shader correctly?
Thanks in advance.

Answer 1

The following is wrong for a start. The Pitch of your input data is the number of bytes per row of the texture, not per pixel.
InitData.SysMemPitch = sizeof(float) * 4;
Secondly:
float4 num = BufferIn.Load(uint3(groupIdx.x, groupIdx.y, 1));
You're trying to load data from the 2nd mip of the texture, it only has 1 mip level.