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Fix animated model skinning precision issues

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#2460
This commit is contained in:
Wojtek Figat
2024-04-22 13:18:52 +02:00
parent 1072b90c5b
commit 568a69081d
5 changed files with 24 additions and 26 deletions
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33
Content/Editor/MaterialTemplates/Surface.shader
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@@ -430,7 +430,9 @@ float3x4 GetPrevBoneMatrix(int index)
float3 SkinPrevPosition(ModelInput_Skinned input)
{
float4 position = float4(input.Position.xyz, 1);
float3x4 boneMatrix = input.BlendWeights.x * GetPrevBoneMatrix(input.BlendIndices.x);
float weightsSum = input.BlendWeights.x + input.BlendWeights.y + input.BlendWeights.z + input.BlendWeights.w;
float mainWeight = input.BlendWeights.x + (1.0f - weightsSum); // Re-normalize to account for 16-bit weights encoding erros
float3x4 boneMatrix = mainWeight * GetPrevBoneMatrix(input.BlendIndices.x);
boneMatrix += input.BlendWeights.y * GetPrevBoneMatrix(input.BlendIndices.y);
boneMatrix += input.BlendWeights.z * GetPrevBoneMatrix(input.BlendIndices.z);
boneMatrix += input.BlendWeights.w * GetPrevBoneMatrix(input.BlendIndices.w);
@@ -439,12 +441,6 @@ float3 SkinPrevPosition(ModelInput_Skinned input)
#endif
// Cached skinning data to avoid multiple calculation
struct SkinningData
{
float3x4 BlendMatrix;
};
// Calculates the transposed transform matrix for the given bone index
float3x4 GetBoneMatrix(int index)
{
@@ -457,7 +453,9 @@ float3x4 GetBoneMatrix(int index)
// Calculates the transposed transform matrix for the given vertex (uses blending)
float3x4 GetBoneMatrix(ModelInput_Skinned input)
{
float3x4 boneMatrix = input.BlendWeights.x * GetBoneMatrix(input.BlendIndices.x);
float weightsSum = input.BlendWeights.x + input.BlendWeights.y + input.BlendWeights.z + input.BlendWeights.w;
float mainWeight = input.BlendWeights.x + (1.0f - weightsSum); // Re-normalize to account for 16-bit weights encoding erros
float3x4 boneMatrix = mainWeight * GetBoneMatrix(input.BlendIndices.x);
boneMatrix += input.BlendWeights.y * GetBoneMatrix(input.BlendIndices.y);
boneMatrix += input.BlendWeights.z * GetBoneMatrix(input.BlendIndices.z);
boneMatrix += input.BlendWeights.w * GetBoneMatrix(input.BlendIndices.w);
@@ -465,13 +463,13 @@ float3x4 GetBoneMatrix(ModelInput_Skinned input)
}
// Transforms the vertex position by weighted sum of the skinning matrices
float3 SkinPosition(ModelInput_Skinned input, SkinningData data)
float3 SkinPosition(ModelInput_Skinned input, float3x4 boneMatrix)
{
return mul(data.BlendMatrix, float4(input.Position.xyz, 1));
return mul(boneMatrix, float4(input.Position.xyz, 1));
}
// Transforms the vertex position by weighted sum of the skinning matrices
float3x3 SkinTangents(ModelInput_Skinned input, SkinningData data)
float3x3 SkinTangents(ModelInput_Skinned input, float3x4 boneMatrix)
{
// Unpack vertex tangent frame
float bitangentSign = input.Tangent.w ? -1.0f : +1.0f;
@@ -479,10 +477,10 @@ float3x3 SkinTangents(ModelInput_Skinned input, SkinningData data)
float3 tangent = input.Tangent.xyz * 2.0 - 1.0;
// Apply skinning
tangent = mul(data.BlendMatrix, float4(tangent, 0));
normal = mul(data.BlendMatrix, float4(normal, 0));
tangent = normalize(mul(boneMatrix, float4(tangent, 0)));
normal = normalize(mul(boneMatrix, float4(normal, 0)));
float3 bitangent = cross(normal, tangent) * bitangentSign;
float3 bitangent = normalize(cross(normal, tangent) * bitangentSign);
return float3x3(tangent, bitangent, normal);
}
@@ -501,10 +499,9 @@ VertexOutput VS_Skinned(ModelInput_Skinned input)
VertexOutput output;
// Perform skinning
SkinningData data;
data.BlendMatrix = GetBoneMatrix(input);
float3 position = SkinPosition(input, data);
float3x3 tangentToLocal = SkinTangents(input, data);
float3x4 boneMatrix = GetBoneMatrix(input);
float3 position = SkinPosition(input, boneMatrix);
float3x3 tangentToLocal = SkinTangents(input, boneMatrix);
// Compute world space vertex position
CalculateInstanceTransform(input);