Henrik Poulsen's Website

I recently got the idea to try to create a procedural shader system for DirectX 11. This basically entails that one simply throws a mesh at the shader generator and it generates a customized shader for this mesh that suits it perfectly.
I knew it is being done in high-end game engines but I had no idea how one actually does it. I spent quite a lot of time on google trying to find this, but it basically looks like some universal secret even though it actually is quite simple. So I played around with it a bit and I managed to get it to work in the end. So the follow code snippet is the procedure I used for getting it to work, probably a whole load of other ones out there.
Just hope this saves other people the same frustrations I had for a while.

void GenerateShader()
{
        ostringstream shader;

        // Basic Vertex Shader
	shader << "float4 BasicVS( float4 Pos : POSITION ) : SV_POSITION" << endl;
	shader << "{" << endl;
	shader << "	return Pos;" << endl;
	shader << "}" << endl;

        // Basic Pixel Shader
	shader << "float4 BasicPS( float4 Pos : SV_POSITION ) : SV_Target" << endl;
	shader <<"{" << endl;
	shader <<"	return float4( 1.0f, 1.0f, 1.0f, 1.0f );" << endl;
	shader <<"}" << endl;

        // A standard DirectX 10 technique
	shader << "technique10 DefaultTechnique" << endl;
	shader << "{" << endl;
	shader << "	pass p0" << endl;
	shader << "	{" << endl;
	shader << "		SetGeometryShader(NULL);" << endl;
	shader << "		SetVertexShader(CompileShader(vs_4_0, BasicVS()));" << endl;
	shader << "		SetPixelShader(CompileShader(ps_4_0, BasicPS()));" << endl;
	shader << "	}" << endl;
	shader << "}" << endl;         

        // This is where the "magic" is at. Grab the char* from your stringstream
        // and feed it into D3DCompile() along with whatever other parameters you usually send it.
        ID3DBlob* errorBlob;
        unsigned int shaderSize = shader.str().size() * sizeof(char);
        HRESULT hr = D3DCompile(shader.str().c_str(), shaderSize, "none", 0, 0, "DefaultTechnique",
                                          "fx_4_0", D3D10_SHADER_ENABLE_STRICTNESS, 0, &blob_, &errorBlob);
	if( FAILED(hr) )
        {
                OutputDebugStringA( (char*)errorBlob->GetBufferPointer() );
	}
	SAFE_RELEASE( errorBlob );
}

So now all that is left is 99.9% of the work to actually switch case together a shader that supports all the things your different meshes might need.
Maybe I will post something on that later when I manage to make a dent in that daunting task :p

Tags: 3D, 3D Engine, Bad excuse for not blogging more often, char*, D3DCompile, DirectX, DirectX 10, DirectX 11, DirectX 9, game, Game Programming, generate, generate shader, generation, HLSL, mesh, model, pixel, pixel shader, procedural, procedural shader, Programming, shader, shader generation, shader generator, stringstream, vertex, vertex shader