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Asked: 2026-05-24T16:41:35+00:00

I’ve got a question about a PixelShader I am trying to implement, and what

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I’ve got a question about a PixelShader I am trying to implement, and what I currently do (this is just for debugging, and trying to figure stuff out):

    int3 loc;
    loc.x = (int)(In.TextureUV.x * resolution_XY.x);
    loc.y = (int)(In.TextureUV.x * resolution_XY.x);
    loc.z = 0;

    float4 r = g_txDiffuse.Load(loc);
    return float4(r.x, r.y, r.z, 1);

The point is, this is always 0,0,0,1

The texture buffer is created:

D3D11_TEXTURE2D_DESC tDesc;
tDesc.Height = 480;
tDesc.Width = 640;
tDesc.Usage = D3D11_USAGE_DYNAMIC;
tDesc.MipLevels = 1;
tDesc.ArraySize = 1;
tDesc.SampleDesc.Count = 1;
tDesc.SampleDesc.Quality = 0;
tDesc.Format = DXGI_FORMAT_R8_UINT;
tDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
tDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
tDesc.MiscFlags = 0;

V_RETURN(pd3dDevice->CreateTexture2D(&tDesc, NULL, &g_pCurrentImage));

I upload the texture (which should be a live display at the end) via:

    D3D11_MAPPED_SUBRESOURCE resource;
    pd3dImmediateContext->Map(g_pCurrentImage, 0, D3D11_MAP_WRITE_DISCARD, 0, &resource);
    memcpy( resource.pData, g_Images.GetData(), g_Images.GetDataSize() );
    pd3dImmediateContext->Unmap( g_pCurrentImage, 0 );

I’ve checked the resource.pData, the data in there is a valid 8bit monochrome image. I made sure the data coming from the camera is 8bit monochrome 640×480.

There’s a few things I don’t fully understand:

  • if I run the Map / memcpy / Unmap routine in every frame, the driver will ultimately crash, the system will be unresponsive. Is there a different way to update a complete texture every frame which should be done?
  • the texture I uploaded is 8bit, why is the Texture2D.load() a float4 return? Do I have to use a different method to access the texture data? I tried to .sample it, but that didn’t work either. Would I have to use a int buffer or something instead?
  • is there a way to debug the GPU memory, to check if the memcpy worked in the first place?
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1 Answer

  1. Editorial Team

    • The Map, memcpy, Unmap really ought not to crash unless2 you are trying to copy too much data into the texture. It would be interesting to know what “GetDataSize()” returns. Does it equal 307,200? If its more than that then there lies your problem.

    • Texture2D returns a float4 because thats what you’ve asked for. If you write float r = g_txDiffuse.Load( … ). The 8-bits get extended to a normalised float as part of the load process. Are you sure, btw, that your calculation of “loc” is correct because as you have it now loc.x and loc.y will always be the same.

    • You can debug whats going on with DirectX using PIX. Its a great tool and I highly recommend you familiarise yourself with it.

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