DirectX Tessellation Function for Triangles

Graphics and GPU Programming Programming DX11

Started by PhillipHamlyn November 25, 2016 08:55 PM

1 comment, last by PhillipHamlyn 7 years, 4 months ago

579

Author

November 25, 2016 08:55 PM

Hi - I have the following simple patch function in DX11, but I keep getting rips, and when I look at the wireframe its clear that adjacent edges are not getting the same tessellation factor. The CalcTessFactor() function just does a distance from the camera to the point passed, so should always give the same value for the same edge center that I pass in.

PatchTess patchFunction_Far(InputPatch<VertexToPixel_Far, 3> patch, uint patchID : SV_PrimitiveID)
{
PatchTess pt;

// Compute midpoint on edges, and patch center
float3 e0 = 0.5f*(patch[0].WorldPosition + patch[1].WorldPosition);
float3 e1 = 0.5f*(patch[1].WorldPosition + patch[2].WorldPosition);
float3 e2 = 0.5f*(patch[2].WorldPosition + patch[0].WorldPosition);
float3 c = (patch[0].WorldPosition + patch[1].WorldPosition + patch[2].WorldPosition) / 3.0f;

pt.EdgeTess[0] = CalcTessFactor(e0);
pt.EdgeTess[1] = CalcTessFactor(e1);
pt.EdgeTess[2] = CalcTessFactor(e2);

pt.InsideTess = CalcTessFactor(c);

return pt;
}

My patches are triangles.

Is there something I'm doing trivially wrong here (like assuming that EdgeTess[0] is correctly assumed to be edge 0-1, rather than edge 2->0 for instance ? - its a wild guess..

TeaTreeTim

512

November 26, 2016 12:23 AM

Should be opposite:

struct PatchOutputType

{

float edges[3] : SV_TessFactor;

float inside : SV_InsideTessFactor;

};

PatchOutputType ExamplePatchFunction(InputPatch<HullInputVertice, 3> input)

{

PatchOutputType output;

output.edges[2] = FactorFromPoints(input[0].pos.xy, input[1].pos.xy);

output.edges[0] = FactorFromPoints(input[1].pos.xy, input[2].pos.xy);

output.edges[1] = FactorFromPoints(input[0].pos.xy, input[2].pos.xy);

output.inside = FactorFromPoints((input[0].pos.xy + input[1].pos.xy + input[2].pos.xy) / 3.0f);

return output;

}

http://www.vrmmorpgordie.com/

PhillipHamlyn

579

Author

November 26, 2016 08:23 AM

Thanks TeaTreaTim - that works fine now.

Out of interest, how did you know which of the edge indexes were correct ? I couldn't find any docs on this.

DirectX Tessellation Function for Triangles

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DirectX Tessellation Function for Triangles

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