Tessellation Texture Coordinates
- by Stuart Martin
Firstly some info - I'm using DirectX 11 , C++ and I'm a fairly good programmer but new to tessellation and not a master graphics programmer.
I'm currently implementing a tessellation system for a terrain model, but i have reached a snag. My current system produces a terrain model from a height map complete with multiple texture coordinates, normals, binormals and tangents for rendering. Now when i was using a simple vertex and pixel shader combination everything worked perfectly but since moving to include a hull and domain shader I'm slightly confused and getting strange results. My terrain is a high detail model but the textured results are very large patches of solid colour.
My current setup passes the model data into the vertex shader then through the hull into the domain and then finally into the pixel shader for use in rendering. My only thought is that in my hull shader i pass the information into the domain shader per patch and this is producing the large areas of solid colour because each patch has identical information. Lighting and normal data are also slightly off but not as visibly as texturing.
Below is a copy of my hull shader that does not work correctly because i think the way that i am passing the data through is incorrect. If anyone can help me out but suggesting an alternative way to get the required data into the pixel shader? or by showing me the correct way to handle the data in the hull shader id be very thankful!
cbuffer TessellationBuffer
{
float tessellationAmount;
float3 padding;
};
struct HullInputType
{
float3 position : POSITION;
float2 tex : TEXCOORD0;
float3 normal : NORMAL;
float3 tangent : TANGENT;
float3 binormal : BINORMAL;
float2 tex2 : TEXCOORD1;
};
struct ConstantOutputType
{
float edges[3] : SV_TessFactor;
float inside : SV_InsideTessFactor;
};
struct HullOutputType
{
float3 position : POSITION;
float2 tex : TEXCOORD0;
float3 normal : NORMAL;
float3 tangent : TANGENT;
float3 binormal : BINORMAL;
float2 tex2 : TEXCOORD1;
float4 depthPosition : TEXCOORD2;
};
ConstantOutputType ColorPatchConstantFunction(InputPatch<HullInputType, 3> inputPatch, uint patchId : SV_PrimitiveID)
{
ConstantOutputType output;
output.edges[0] = tessellationAmount;
output.edges[1] = tessellationAmount;
output.edges[2] = tessellationAmount;
output.inside = tessellationAmount;
return output;
}
[domain("tri")]
[partitioning("integer")]
[outputtopology("triangle_cw")]
[outputcontrolpoints(3)]
[patchconstantfunc("ColorPatchConstantFunction")]
HullOutputType ColorHullShader(InputPatch<HullInputType, 3> patch, uint pointId : SV_OutputControlPointID, uint patchId : SV_PrimitiveID)
{
HullOutputType output;
output.position = patch[pointId].position;
output.tex = patch[pointId].tex;
output.tex2 = patch[pointId].tex2;
output.normal = patch[pointId].normal;
output.tangent = patch[pointId].tangent;
output.binormal = patch[pointId].binormal;
return output;
}
Edited to include the domain shader:-
[domain("tri")]
PixelInputType ColorDomainShader(ConstantOutputType input, float3 uvwCoord : SV_DomainLocation, const OutputPatch<HullOutputType, 3> patch)
{
float3 vertexPosition;
PixelInputType output;
// Determine the position of the new vertex.
vertexPosition = uvwCoord.x * patch[0].position + uvwCoord.y * patch[1].position + uvwCoord.z * patch[2].position;
output.position = mul(float4(vertexPosition, 1.0f), worldMatrix);
output.position = mul(output.position, viewMatrix);
output.position = mul(output.position, projectionMatrix);
output.depthPosition = output.position;
output.tex = patch[0].tex;
output.tex2 = patch[0].tex2;
output.normal = patch[0].normal;
output.tangent = patch[0].tangent;
output.binormal = patch[0].binormal;
return output;
}
