3DTexture-based Volume Rendering - c++

Question

I've been trying to get a series of 2D images, all same in size and formatted as a raw data, loaded into a 3D texture and then render that 3D texture on the screen. As I'm still pretty new with DirectX, I'm not sure what I'm doing wrong. Here's the relevant code:
// Open the image and copy its contents into a buffer
std::ifstream image("head256x256x109", std::ifstream::binary);
int size;
char* buffer;
if (image.is_open()) {
image.seekg(0, image.end);
size = image.tellg();
image.seekg(0, image.beg);
buffer = new char[size];
image.read(buffer, size);
image.close();
} else {
return false;
}
// Convert the data to RGBA data
// Here we are simply putting the same value to R, G, B and A channels.
char* RGBABuffer = new char[ size*4 ];
for( int nIndx = 0; nIndx < size; ++nIndx )
{
RGBABuffer[nIndx*4] = buffer[nIndx];
RGBABuffer[nIndx*4+1] = buffer[nIndx];
RGBABuffer[nIndx*4+2] = buffer[nIndx];
RGBABuffer[nIndx*4+3] = buffer[nIndx];
}
// Create the texture
D3D11_TEXTURE3D_DESC texture_desc;
ZeroMemory(&texture_desc, sizeof(texture_desc));
texture_desc.Width = 256;
texture_desc.Height = 256;
texture_desc.Depth = 109;
texture_desc.MipLevels = 1;
texture_desc.Format = DXGI_FORMAT_R32G32B32A32_FLOAT;
texture_desc.Usage = D3D11_USAGE_DEFAULT;
texture_desc.BindFlags = D3D11_BIND_SHADER_RESOURCE;
D3D11_SUBRESOURCE_DATA image_data;
ZeroMemory(&image_data, sizeof(image_data));
image_data.pSysMem = RGBABuffer;
image_data.SysMemPitch = 256 * 4;
image_data.SysMemSlicePitch = 256 * 256 * 4;
d3dResult = d3dDevice_->CreateTexture3D(&texture_desc, &image_data, &texture_);
// Create a sampler
D3D11_SAMPLER_DESC colorMapDesc;
ZeroMemory( &colorMapDesc, sizeof( colorMapDesc ) );
colorMapDesc.AddressU = D3D11_TEXTURE_ADDRESS_WRAP;
colorMapDesc.AddressV = D3D11_TEXTURE_ADDRESS_WRAP;
colorMapDesc.AddressW = D3D11_TEXTURE_ADDRESS_WRAP;
colorMapDesc.ComparisonFunc = D3D11_COMPARISON_NEVER;
colorMapDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_LINEAR;
colorMapDesc.MaxLOD = D3D11_FLOAT32_MAX;
d3dResult = d3dDevice_->CreateSamplerState( &colorMapDesc, &colorMapSampler_ );
Shader code is as simple as possible:
Texture3D colorMap_ : register( t0 );
SamplerState colorSampler_ : register( s0 );
struct VS_Input
{
float4 pos : POSITION;
float4 tex0 : TEXCOORD0;
};
struct PS_Input
{
float4 pos : SV_POSITION;
float4 tex0 : TEXCOORD0;
};
PS_Input VS_Main( VS_Input vertex )
{
PS_Input vsOut = ( PS_Input )0;
vsOut.pos = vertex.pos;
vsOut.tex0 = vertex.tex0;
return vsOut;
}
float4 PS_Main( PS_Input frag ) : SV_TARGET
{
return colorMap_.Sample( colorSampler_, frag.tex0 );
}
Now I know that I would need to implement some sort of alpha blending for this to work properly, but I hoped I would at least get a first slice of the picture shown with this. However, all I get is the background color that I set in my Render function:
float clearColor[4] = { 0.0f, 0.0f, 0.0f, 1.0f };
d3dContext_->ClearRenderTargetView( backBufferTarget_, clearColor );
Any help on what I've might be doing wrong as well as any further tips that I would need to do to achieve this goal (making a 3D texture out of a series of images and render it on screen) would be hugely helpful as there is very little documentation about this on the web.