siege-song/Data/Assets/FluffyGroomingTool/Shaders/Resources/MeshBaker.compute

#pragma kernel BakeMeshKernel
#pragma kernel RayCastKernel

#pragma multi_compile __  IS_SKINNED_MESH
#include "../NormalHelperInclude.cginc"
#include "Thread.hlsl"

struct MeshProperties
{
    float3 sourceVertex;
    float3 sourceNormal;
    float4 sourceTangent;
};

uniform RWByteAddressBuffer sourceMeshData;
uniform uint vertexBufferStride;
uniform RWStructuredBuffer<MeshProperties> bakedMesh;

#define SIZEOF_FLOAT3 12
uniform float4x4 transformMatrix;
uniform float4x4 rotationMatrix;
uniform uint verticesCount;

float3 loadSourceVertex(uint index)
{
    return asfloat(sourceMeshData.Load3(index * vertexBufferStride));
}

float3 loadSourceNormal(uint index)
{
    return mul(rotationMatrix, float4(asfloat(sourceMeshData.Load3(index * vertexBufferStride + SIZEOF_FLOAT3)), 1)).xyz;
}

float4 loadSourceTangent(uint index)
{
    return mul(rotationMatrix, asfloat(sourceMeshData.Load4(index * vertexBufferStride + SIZEOF_FLOAT3 * 2)));
}


THREAD_SIZE
void BakeMeshKernel(uint3 id : SV_DispatchThreadID)
{
    uint index = id.x;
    if (index < verticesCount)
    {
        MeshProperties baked;
        float3 vertex = loadSourceVertex(index);

        baked.sourceVertex = mul(transformMatrix, float4(vertex, 1)).xyz;
        baked.sourceNormal = loadSourceNormal(index);
        baked.sourceTangent = loadSourceTangent(index);
        bakedMesh[index] = baked;
    }
}

float3 origin;
float3 direction;
RWByteAddressBuffer meshIndexBuffer;
AppendStructuredBuffer<MeshProperties> rayCastHits;

bool intersectTriangle(float3 a, float3 b, float3 c, out float3 barycentricCoordinate)
{
    barycentricCoordinate = float3(0, 0, 0);
    bool returnValue = true;
    float3 ro = origin;
    float3 rd = direction;

    float3 ab = b - a;
    float3 ac = c - a;
    float3 n = cross(rd, ac);
    float det = dot(ab, n);
    if (abs(det) < 1e-5)
    {
        returnValue = false;
    }
    else
    {
        float invDet = 1.0 / det;
        float3 k = ro - a;
        float u = dot(k, n) * invDet;
        if (u < 0.0 || u > 1.0)
        {
            returnValue = false;
        }
        else
        {
            float v = dot(rd, cross(k, ab)) * invDet;
            if (v < 0.0 || u + v > 1.0)
            {
                returnValue = false;
            }
            else
            {
                float w = 1.0f - u - v;
                barycentricCoordinate = float3(u, v, w);
            }
        }
    }


    return returnValue;
}

MeshProperties getBarycentricMeshData(MeshProperties mp1, MeshProperties mp2, MeshProperties mp3, float3 barycentricCoord)
{
    MeshProperties interpolated;
    interpolated.sourceVertex = Interpolate3(mp1.sourceVertex, mp2.sourceVertex, mp3.sourceVertex, barycentricCoord);
    interpolated.sourceNormal = Interpolate3(mp1.sourceNormal, mp2.sourceNormal, mp3.sourceNormal, barycentricCoord);
    interpolated.sourceTangent = Interpolate4(mp1.sourceTangent, mp2.sourceTangent, mp3.sourceTangent, barycentricCoord);
    return interpolated;
}

MeshProperties createWorldPosMeshProperty(float3 worldVertex, MeshProperties mp)
{
    MeshProperties meshProperty;
    meshProperty.sourceVertex = worldVertex;
    meshProperty.sourceNormal = mp.sourceNormal;
    meshProperty.sourceTangent = mp.sourceTangent;
    return meshProperty;
}

THREAD_SIZE_EDITOR
void RayCastKernel(uint3 id : SV_DispatchThreadID)
{
    uint triangle1Index1 = id.x * 3;
    uint triangle1Index2 = triangle1Index1 + 1;
    uint triangle1Index3 = triangle1Index1 + 2;

    triangle1Index1 = meshIndexBuffer.Load(triangle1Index1 * 4);
    triangle1Index2 = meshIndexBuffer.Load(triangle1Index2 * 4);
    triangle1Index3 = meshIndexBuffer.Load(triangle1Index3 * 4);
    MeshProperties mp1 = bakedMesh[triangle1Index1];
    MeshProperties mp2 = bakedMesh[triangle1Index2];
    MeshProperties mp3 = bakedMesh[triangle1Index3];

    float3 worldVertex1 = mul(transformMatrix, float4(mp1.sourceVertex, 1)).xyz;
    float3 worldVertex2 = mul(transformMatrix, float4(mp2.sourceVertex, 1)).xyz;
    float3 worldVertex3 = mul(transformMatrix, float4(mp3.sourceVertex, 1)).xyz;

    float3 baryCentricCoordinate;

    if (intersectTriangle(worldVertex3, worldVertex1, worldVertex2, baryCentricCoordinate))
    {
        MeshProperties meshData = getBarycentricMeshData(
            createWorldPosMeshProperty(worldVertex1, mp1),
            createWorldPosMeshProperty(worldVertex2, mp2),
            createWorldPosMeshProperty(worldVertex3, mp3)
            , baryCentricCoordinate
        );
        meshData.sourceNormal = mul(rotationMatrix, float4(meshData.sourceNormal, 1)).xyz;
        meshData.sourceTangent = mul(rotationMatrix, meshData.sourceTangent);
        rayCastHits.Append(
            meshData
        );
    }
}