Using unsigned byte textures with DirectX 10 / 11 - c++

Question

I am attempting to do some processing in the pixel shader on a texture. The data for the texture is coming from a memory chunk of 8 bit data. The problem I am facing is how to read the data in the shader.
Code to create the texture and ressource view:
In OnD3D11CreateDevice:
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));
D3D11_SHADER_RESOURCE_VIEW_DESC rvDesc;
g_pCurrentImage->GetDesc(&tDesc);
rvDesc.Format = DXGI_FORMAT_R8_UINT;
rvDesc.Texture2D.MipLevels = tDesc.MipLevels;
rvDesc.Texture2D.MostDetailedMip = tDesc.MipLevels - 1;
rvDesc.ViewDimension = D3D_SRV_DIMENSION_TEXTURE2D;
V_RETURN(pd3dDevice->CreateShaderResourceView(g_pCurrentImage, &rvDesc, &g_pImageRV)); </code>
in OnD3D11FrameRender:
HRESULT okay;
if( !g_updateDone ) {
D3D11_MAPPED_SUBRESOURCE resource;
resource.pData = mImage.GetData();
resource.RowPitch = 640;
resource.DepthPitch = 1;
okay = pd3dImmediateContext->Map(g_pCurrentImage, 0, D3D11_MAP_WRITE_DISCARD, 0, &resource);
g_updateDone = true;
}
pd3dImmediateContext->PSSetShaderResources(0, 1, &g_pImageRV);
This returns no errors so far, everything seems to work.
The HLSL Shader:
//-----
// Textures and Samplers
//-----
Texture2D <int> g_txDiffuse : register( t0 );
SamplerState g_samLinear : register( s0 );
//-----
// shader input/output structure
//-----
struct VS_INPUT
{
float4 Position : POSITION; // vertex position
float2 TextureUV : TEXCOORD0;// vertex texture coords
};
struct VS_OUTPUT
{
float4 Position : SV_POSITION; // vertex position
float2 TextureUV : TEXCOORD0; // vertex texture coords
};
//-----
// Vertex shader
//-----
VS_OUTPUT RenderSceneVS( VS_INPUT input )
{
VS_OUTPUT Output;
Output.Position = input.Position;
Output.TextureUV = input.TextureUV;
return Output;
}
//-----
// Pixel Shader
//-----
float4 RenderScenePS( VS_OUTPUT In ) : SV_TARGET
{
int3 loc;
loc.x = 0;
loc.y = 0;
loc.z = 1;
int r = g_txDiffuse.Load(loc);
//float fTest = (float) r;
return float4( In.TextureUV.x, In.TextureUV.y, In.TextureUV.x + In.TextureUV.y, 1);
}
The thing is, I can't even debug it in PIX to see what r results in, because even with Shader optimization disabled, the line int r = ... is never reached
I tested
float fTest = (float) r;
return float4( In.TextureUV.x, In.TextureUV.y, In.TextureUV.x + In.TextureUV.y, fTest);
but this would result in "cannot map expression to pixel shader instruction set", even though it's a float.
So how do I read and use 8bit integers from a texture, and if possible, with no sampling at all.
Thanks for any feedback.

Answer 1

Oh my this is a really old question, I thought it said 2012!
But anyway as it's still open:
Due to the nature of GPU's being optimised for floating point arithmetic, you probably wont get a great deal of performance advantage by using a Texture2D<int> over a Texture2D<float>.
You could attempt to use a Texture2D<float> and then try:
return float4( In.TextureUV.x, In.TextureUV.y, In.TextureUV.x + In.TextureUV.y, g_txDiffuse.Load(loc));

Answer 2

loc.z = 1;
Should be 0 here, because texture mip levels is 1 in your case, and mipmaps start at 0 in HLSL for Load intrinsic.