glslShader/crackFreePrimitiveGenerator.cpp

//-
// ==========================================================================
// Copyright 2015 Autodesk, Inc.  All rights reserved.
//
// Use of this software is subject to the terms of the Autodesk
// license agreement provided at the time of installation or download,
// or which otherwise accompanies this software in either electronic
// or hard copy form.
// ==========================================================================
//+

// Example plugin: crackFreePrimitiveGenerator.cpp
//
// This plug-in is an example of a custom MPxIndexBufferMutator.
// It provides custom primitives based on shader requirements coming from 
// an MPxShaderOverride.  The name() in the MIndexBufferDescriptor is used 
// to signify a unique identifier for a custom buffer.

#include "crackFreePrimitiveGenerator.h"
#include <maya/MStatus.h>
#include <maya/MFnMesh.h>
#include <maya/MIntArray.h>
#include <maya/MFloatArray.h>
#include <maya/MPxVertexBufferGenerator.h>
#include <maya/MHWGeometry.h>
#include <maya/MDrawRegistry.h>
#include <maya/MComponentDataIndexing.h>
#include <map>

namespace
{
    struct Edge
    {
        Edge(unsigned int v0_ = 0, unsigned int v1_ = 0) : v0(v0_), v1(v1_) {}

        Edge reversed() const
        {
            return Edge(v1, v0);
        }

        bool isEqual(const Edge &rhs) const
        {
            return (v0 == rhs.v0 && v1 == rhs.v1);
        }

        bool isReverse(const Edge &rhs) const
        {
            return (v0 == rhs.v1 && v1 == rhs.v0);
        }

        unsigned int v0;
        unsigned int v1;
    };

    bool operator< (const Edge& lhs, const Edge& rhs)
    {
        return (lhs.v0 < rhs.v0) || (lhs.v0 == rhs.v0 && lhs.v1 < rhs.v1);
    }

    class EdgeMapping
    {
    public:
        EdgeMapping();

        void addTriangle(unsigned int faceVertexId0, unsigned int faceVertexId1, unsigned int faceVertexId2, unsigned int polyVertexId0, unsigned int polyVertexId1, unsigned int polyVertexId2);
        void addEdge(const Edge& faceEdge, const Edge& polyEdge);

        void addPositionUV(unsigned int faceVertexId, unsigned int polyVertexId, float u, float v);

        bool adjacentEdge(const Edge& faceEdge, Edge& adjacentEdge) const;

        bool dominantEdge(const Edge& faceEdge, Edge& dominantEdge) const;

        bool dominantPosition(unsigned int faceVertexId, unsigned int& dominantVertexId) const;

    private:
        // Map each face edge to its polygon edge.
        typedef std::map< Edge, Edge > FaceEdge2PolyEdgeMap;
        FaceEdge2PolyEdgeMap fFaceEdge2PolyEdgeMap;

        // Map each poly edge to both face edges that match.
        typedef std::map< Edge, std::pair< Edge, Edge > > PolyEdge2FaceEdgeMap;
        PolyEdge2FaceEdgeMap fPolyEdge2FaceEdgesMap;

        // Map a single face vertex id to its polygon vertex id.
        typedef std::map< unsigned int, unsigned int > FaceVertex2PolyVertexMap;
        FaceVertex2PolyVertexMap fFaceVertex2PolyVertexMap;

        // Map dominant vertex position via lowest uv coords.
        typedef std::pair< unsigned int, std::pair< float, float > > VertexUVPair;
        typedef std::map< unsigned int, VertexUVPair > PolyVertex2FaceVertexUVMap;
        PolyVertex2FaceVertexUVMap fPolyVertex2FaceVertexUVMap;
    };

    EdgeMapping::EdgeMapping()
    {
    }

    void EdgeMapping::addTriangle(unsigned int faceVertexId0, unsigned int faceVertexId1, unsigned int faceVertexId2, unsigned int polyVertexId0, unsigned int polyVertexId1, unsigned int polyVertexId2)
    {
        addEdge( Edge(faceVertexId0, faceVertexId1), Edge(polyVertexId0, polyVertexId1) );
        addEdge( Edge(faceVertexId1, faceVertexId2), Edge(polyVertexId1, polyVertexId2) );
        addEdge( Edge(faceVertexId2, faceVertexId0), Edge(polyVertexId2, polyVertexId0) );
    }

    // Add a new edge
    // The edge is represented by two associated vertex ids pairs : one in face vertices array space and a second in polygon face vertices array space.
    void EdgeMapping::addEdge(const Edge& faceEdge, const Edge& polyEdge)
    {
        if(polyEdge.v1 < polyEdge.v0)
        {
            // Revert edges
            Edge faceEdgeR = faceEdge.reversed();
            Edge polyEdgeR = polyEdge.reversed();
            addEdge(faceEdgeR, polyEdgeR);
            return;
        }

        fFaceEdge2PolyEdgeMap[faceEdge] = polyEdge;
        
        PolyEdge2FaceEdgeMap::iterator itP2F = fPolyEdge2FaceEdgesMap.find( polyEdge );
        if(itP2F == fPolyEdge2FaceEdgesMap.end())
        {
            fPolyEdge2FaceEdgesMap[polyEdge] = std::make_pair( faceEdge, faceEdge );
        }
        else
        {
            itP2F->second.second = faceEdge;
        }
    }

    void EdgeMapping::addPositionUV(unsigned int faceVertexId, unsigned int polyVertexId, float u, float v)
    {
        fFaceVertex2PolyVertexMap[faceVertexId] = polyVertexId;

        PolyVertex2FaceVertexUVMap::iterator it = fPolyVertex2FaceVertexUVMap.find(polyVertexId);
        if(it == fPolyVertex2FaceVertexUVMap.end())
        {
            fPolyVertex2FaceVertexUVMap[polyVertexId] = std::make_pair( faceVertexId, std::make_pair(u,v) );
        }
        else
        {
            VertexUVPair& vertexUVPair = it->second;
            float lastU = vertexUVPair.second.first;
            float lastV = vertexUVPair.second.second;
            if( u < lastU || ( u == lastU && v < lastV ) )
            {
                vertexUVPair.first = faceVertexId;
                vertexUVPair.second = std::make_pair(u,v);
            }
        }
    }

    // Find the adjacent edge that is shared between two faces.
    // The matching is done through the polygon vertex ids.
    // The returning edge have vertices in face space.
    bool EdgeMapping::adjacentEdge(const Edge& faceEdge, Edge& adjacentEdge) const
    {
        FaceEdge2PolyEdgeMap::const_iterator itF2P = fFaceEdge2PolyEdgeMap.find( faceEdge );
        if(itF2P == fFaceEdge2PolyEdgeMap.end())
        {
            Edge faceEdgeR = faceEdge.reversed();
            itF2P = fFaceEdge2PolyEdgeMap.find( faceEdgeR );
            if(itF2P == fFaceEdge2PolyEdgeMap.end())
                return false;
        }

        const Edge& polyEdge = itF2P->second;

        PolyEdge2FaceEdgeMap::const_iterator itP2F = fPolyEdge2FaceEdgesMap.find( polyEdge );
        if(itP2F == fPolyEdge2FaceEdgesMap.end())
            return false;

        const Edge& faceEdge0 = itP2F->second.first;
        const Edge& faceEdge1 = itP2F->second.second;

        bool foundMatch = false;
        if(faceEdge.isEqual(faceEdge0))
        {
            adjacentEdge = faceEdge1;
            foundMatch = true;
        }
        else if(faceEdge.isReverse(faceEdge0))
        {
            adjacentEdge = faceEdge1.reversed();
            foundMatch = true;
        }
        else if(faceEdge.isEqual(faceEdge1))
        {
            adjacentEdge = faceEdge0;
            foundMatch = true;
        }
        else if(faceEdge.isReverse(faceEdge1))
        {
            adjacentEdge = faceEdge0.reversed();
            foundMatch = true;
        }

        return foundMatch;
    }

    bool EdgeMapping::dominantEdge(const Edge& faceEdge, Edge& dominantEdge) const
    {
        bool returnReversed = true;
        FaceEdge2PolyEdgeMap::const_iterator itF2P = fFaceEdge2PolyEdgeMap.find( faceEdge );
        if(itF2P == fFaceEdge2PolyEdgeMap.end())
        {
            Edge faceEdgeR = faceEdge.reversed();
            itF2P = fFaceEdge2PolyEdgeMap.find( faceEdgeR );
            if(itF2P == fFaceEdge2PolyEdgeMap.end())
                return false;
            returnReversed = false;
        }

        const Edge& polyEdge = itF2P->second;

        PolyEdge2FaceEdgeMap::const_iterator itP2F = fPolyEdge2FaceEdgesMap.find( polyEdge );
        if(itP2F == fPolyEdge2FaceEdgesMap.end())
            return false;

        const Edge& faceEdge0 = itP2F->second.first;
        const Edge& faceEdge1 = itP2F->second.second;

        if(faceEdge0 < faceEdge1)
        {
            dominantEdge = (returnReversed ? faceEdge0.reversed() : faceEdge0);
        }
        else
        {
            dominantEdge = (returnReversed ? faceEdge1.reversed() : faceEdge1);
        }

        return true;
    }

    bool EdgeMapping::dominantPosition(unsigned int faceVertexId, unsigned int& dominantVertexId) const
    {
        FaceVertex2PolyVertexMap::const_iterator itF2P = fFaceVertex2PolyVertexMap.find(faceVertexId);
        if(itF2P == fFaceVertex2PolyVertexMap.end())
            return false;

        unsigned polyVertexId = itF2P->second;

        PolyVertex2FaceVertexUVMap::const_iterator itP2FUV = fPolyVertex2FaceVertexUVMap.find(polyVertexId);
        if(itP2FUV == fPolyVertex2FaceVertexUVMap.end())
            return false;

        dominantVertexId = itP2FUV->second.first;
        return true;
    }

    struct VertexF
    {
        static const float kTolerance;
        VertexF(const float* buffer, unsigned int index)
        {
            unsigned int bufferPos = index * 3;
            x = buffer[bufferPos++];
            y = buffer[bufferPos++];
            z = buffer[bufferPos++];
        }

        bool isEqual(const VertexF &rhs) const
        {
            return (fabs(x - rhs.x) < kTolerance && fabs(y - rhs.y) < kTolerance && fabs(z - rhs.z) < kTolerance);
        }

        float x, y, z;
    };

    const float VertexF::kTolerance = 1e-5f;

    bool operator< (const VertexF& lhs, const VertexF& rhs)
    {
        return ((lhs.x - rhs.x) < -VertexF::kTolerance) || 
               (fabs(lhs.x - rhs.x) < VertexF::kTolerance && (lhs.y - rhs.y) < -VertexF::kTolerance) || 
               (fabs(lhs.x - rhs.x) < VertexF::kTolerance && fabs(lhs.y - rhs.y) < VertexF::kTolerance && (lhs.z - rhs.z) < -VertexF::kTolerance);
    }

    struct VertexFMap
    {
        unsigned int getVertexId( const VertexF& v );

        typedef std::map<VertexF, unsigned int> TVtxMap;
        TVtxMap vertexMap;
    };

    unsigned int VertexFMap::getVertexId( const VertexF& v )
    {
        VertexFMap::TVtxMap::const_iterator itVtx = vertexMap.find(v);
        if (itVtx != vertexMap.end())
            return itVtx->second;
        unsigned int nextId = (unsigned int)vertexMap.size();
        vertexMap.insert(TVtxMap::value_type(v,nextId));
        return nextId;
    }
}

// Mode 1 : PN Triangles; no divergent normals and no displacement crack fix
// Mode 2 : PN AEN, divergent normals crack fix; no displacement UV seam crack fix
// Mode 3 : PN AEN, crack fix for divergent normals and UV seam displacement


CrackFreePrimitiveGenerator::CrackFreePrimitiveGenerator(bool addAdjacentEdges, bool addDominantEdges, bool addDominantPosition)
: fAddAdjacentEdges(addAdjacentEdges)
, fAddDominantEdges(addDominantEdges)
, fAddDominantPosition(addDominantPosition)
{
}

CrackFreePrimitiveGenerator::~CrackFreePrimitiveGenerator() {}

unsigned int CrackFreePrimitiveGenerator::computeTriangleSize(bool bAddAdjacentEdges,
                        bool bAddDominantEdges,
                        bool bAddDominantPosition)
{
    return 3                                /* triangles vertices */
        + (bAddAdjacentEdges ? 3 * 2 : 0)   /* adjacent edges */
        + (bAddDominantEdges ? 3 * 2 : 0)   /* dominant edges */
        + (bAddDominantPosition ? 3 : 0);   /* dominant position */
}

void CrackFreePrimitiveGenerator::mutateIndexBuffer( const MUintArray& originalBufferIndices, 
                        const float* positionBufferFloat, 
                        const float* uvBufferFloat, 
                        bool bAddAdjacentEdges,
                        bool bAddDominantEdges,
                        bool bAddDominantPosition,
                        MHWRender::MGeometry::DataType indexBufferDataType,
                        void* indexData )
{
    unsigned int numTriVerts = originalBufferIndices.length();

    EdgeMapping edges;
    {
        VertexFMap vertexMap;

        // Iterate all triangles found in the old index buffer:
        unsigned int vertexIndex = 0;

        while (vertexIndex < numTriVerts)
        {
            unsigned int faceVertexId0 = originalBufferIndices[vertexIndex++];
            unsigned int polyVertexId0 = vertexMap.getVertexId(VertexF(positionBufferFloat, faceVertexId0));

            unsigned int faceVertexId1 = originalBufferIndices[vertexIndex++];
            unsigned int polyVertexId1 = vertexMap.getVertexId(VertexF(positionBufferFloat, faceVertexId1));

            unsigned int faceVertexId2 = originalBufferIndices[vertexIndex++];
            unsigned int polyVertexId2 = vertexMap.getVertexId(VertexF(positionBufferFloat, faceVertexId2));

            edges.addTriangle(faceVertexId0, faceVertexId1, faceVertexId2, polyVertexId0, polyVertexId1, polyVertexId2);

            if(bAddDominantPosition && uvBufferFloat)
            {
                unsigned int uvIndex;
                uvIndex = faceVertexId0 * 2;
                edges.addPositionUV(faceVertexId0, polyVertexId0, uvBufferFloat[uvIndex], uvBufferFloat[uvIndex+1]);

                uvIndex = faceVertexId1 * 2;
                edges.addPositionUV(faceVertexId1, polyVertexId1, uvBufferFloat[uvIndex], uvBufferFloat[uvIndex+1]);

                uvIndex = faceVertexId2 * 2;
                edges.addPositionUV(faceVertexId2, polyVertexId2, uvBufferFloat[uvIndex], uvBufferFloat[uvIndex+1]);
            }
        }
    }

    unsigned int newTriId = 0;
    for(unsigned int triId = 0; triId < numTriVerts; )
    {
        unsigned int vertexId0 = originalBufferIndices[triId++];
        unsigned int vertexId1 = originalBufferIndices[triId++];
        unsigned int vertexId2 = originalBufferIndices[triId++];

        if (indexBufferDataType == MHWRender::MGeometry::kUnsignedInt32) {
            // Triangle vertices
            ((unsigned int*)indexData)[newTriId++] = vertexId0;
            ((unsigned int*)indexData)[newTriId++] = vertexId1;
            ((unsigned int*)indexData)[newTriId++] = vertexId2;

            // Adjacent edges
            if(bAddAdjacentEdges)
            {
                Edge adjacentEdge;

                // Edge0 : vertexId0 - vertexId1
                edges.adjacentEdge(Edge(vertexId0, vertexId1), adjacentEdge);
                ((unsigned int*)indexData)[newTriId++] = adjacentEdge.v0;
                ((unsigned int*)indexData)[newTriId++] = adjacentEdge.v1;

                // Edge1 : vertexId1 - vertexId2
                edges.adjacentEdge(Edge(vertexId1, vertexId2), adjacentEdge);
                ((unsigned int*)indexData)[newTriId++] = adjacentEdge.v0;
                ((unsigned int*)indexData)[newTriId++] = adjacentEdge.v1;

                // Edge2 : vertexId2 - vertexId0
                edges.adjacentEdge(Edge(vertexId2, vertexId0), adjacentEdge);
                ((unsigned int*)indexData)[newTriId++] = adjacentEdge.v0;
                ((unsigned int*)indexData)[newTriId++] = adjacentEdge.v1;
            }

            // Dominant edges
            if(bAddDominantEdges)
            {
                Edge dominantEdge;

                // Edge0 : vertexId0 - vertexId1
                edges.dominantEdge(Edge(vertexId0, vertexId1), dominantEdge);
                ((unsigned int*)indexData)[newTriId++] = dominantEdge.v0;
                ((unsigned int*)indexData)[newTriId++] = dominantEdge.v1;

                // Edge1 : vertexId1 - vertexId2
                edges.dominantEdge(Edge(vertexId1, vertexId2), dominantEdge);
                ((unsigned int*)indexData)[newTriId++] = dominantEdge.v0;
                ((unsigned int*)indexData)[newTriId++] = dominantEdge.v1;

                // Edge2 : vertexId2 - vertexId0
                edges.dominantEdge(Edge(vertexId2, vertexId0), dominantEdge);
                ((unsigned int*)indexData)[newTriId++] = dominantEdge.v0;
                ((unsigned int*)indexData)[newTriId++] = dominantEdge.v1;
            }

            // Dominant position
            if(bAddDominantPosition)
            {
                unsigned int dominantVertexId;

                edges.dominantPosition(vertexId0, dominantVertexId);
                ((unsigned int*)indexData)[newTriId++] = dominantVertexId;

                edges.dominantPosition(vertexId1, dominantVertexId);
                ((unsigned int*)indexData)[newTriId++] = dominantVertexId;

                edges.dominantPosition(vertexId2, dominantVertexId);
                ((unsigned int*)indexData)[newTriId++] = dominantVertexId;
            }
        }
        else if (indexBufferDataType == MHWRender::MGeometry::kUnsignedChar) {
            ((unsigned short*)indexData)[newTriId++] = (unsigned short)vertexId0;
            ((unsigned short*)indexData)[newTriId++] = (unsigned short)vertexId1;
            ((unsigned short*)indexData)[newTriId++] = (unsigned short)vertexId2;

            // Adjacent edges
            if(bAddAdjacentEdges)
            {
                Edge adjacentEdge;

                // Edge0 : vertexId0 - vertexId1
                edges.adjacentEdge(Edge(vertexId0, vertexId1), adjacentEdge);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)adjacentEdge.v0;
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)adjacentEdge.v1;

                // Edge1 : vertexId1 - vertexId2
                edges.adjacentEdge(Edge(vertexId1, vertexId2), adjacentEdge);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)adjacentEdge.v0;
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)adjacentEdge.v1;

                // Edge2 : vertexId2 - vertexId0
                edges.adjacentEdge(Edge(vertexId2, vertexId0), adjacentEdge);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)adjacentEdge.v0;
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)adjacentEdge.v1;
            }

            // Dominant edges
            if(bAddDominantEdges)
            {
                Edge dominantEdge;

                // Edge0 : vertexId0 - vertexId1
                edges.dominantEdge(Edge(vertexId0, vertexId1), dominantEdge);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantEdge.v0;
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantEdge.v1;

                // Edge1 : vertexId1 - vertexId2
                edges.dominantEdge(Edge(vertexId1, vertexId2), dominantEdge);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantEdge.v0;
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantEdge.v1;

                // Edge2 : vertexId2 - vertexId0
                edges.dominantEdge(Edge(vertexId2, vertexId0), dominantEdge);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantEdge.v0;
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantEdge.v1;
            }

            // Dominant position
            if(bAddDominantPosition)
            {
                unsigned int dominantVertexId;

                edges.dominantPosition(vertexId0, dominantVertexId);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantVertexId;

                edges.dominantPosition(vertexId1, dominantVertexId);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantVertexId;

                edges.dominantPosition(vertexId2, dominantVertexId);
                ((unsigned short*)indexData)[newTriId++] = (unsigned short)dominantVertexId;
            }
        }
    }
}


MHWRender::MGeometry::Primitive CrackFreePrimitiveGenerator::mutateIndexing(const MHWRender::MComponentDataIndexingList& sourceIndexBuffers, 
        const MHWRender::MVertexBufferArray& vertexBuffers,
        MHWRender::MIndexBuffer& indexBuffer,
        int& primitiveStride) const
{
    MHWRender::MVertexBuffer *positionBuffer = NULL;
    MHWRender::MVertexBuffer *uvBuffer = NULL;
    
    for (unsigned int ivb = 0; ivb < vertexBuffers.count() && (positionBuffer == NULL || uvBuffer == NULL); ++ivb)
    {
        MHWRender::MVertexBuffer *currBuffer = vertexBuffers.getBuffer(ivb);

        if (positionBuffer == NULL && currBuffer->descriptor().semantic() == MHWRender::MGeometry::kPosition)
            positionBuffer = currBuffer;

        if (uvBuffer == NULL && currBuffer->descriptor().semantic() == MHWRender::MGeometry::kTexture)
            uvBuffer = currBuffer;
    }

    if (positionBuffer == NULL)
        // We need at least the positions:
        return MHWRender::MGeometry::kInvalidPrimitive;

    float* positionBufferFloat = (float*)positionBuffer->map();
    float* uvBufferFloat = NULL;
    if (uvBuffer)
        uvBufferFloat = (float*)uvBuffer->map();

    for (int x = 0; x < sourceIndexBuffers.length(); ++x)
    {
        if (sourceIndexBuffers[x]->componentType() != MHWRender::MComponentDataIndexing::kFaceVertex)
            continue;

        const MUintArray& originalBufferIndices = sourceIndexBuffers[x]->indices();
        unsigned int numTriVerts = originalBufferIndices.length();

        unsigned int numTri = numTriVerts / 3;
        unsigned int triSize = computeTriangleSize(fAddAdjacentEdges, fAddDominantEdges, fAddDominantPosition);
        unsigned int bufferSize = numTri * triSize;

        void* indexData = indexBuffer.acquire(bufferSize, true /*writeOnly - we don't need the current buffer values*/);
        if (indexData != NULL)
        {
            mutateIndexBuffer( originalBufferIndices, positionBufferFloat, uvBufferFloat, 
                               fAddAdjacentEdges, fAddDominantEdges, fAddDominantPosition,
                               indexBuffer.dataType(), indexData );
        }

        if (positionBuffer) positionBuffer->unmap();
        if (uvBuffer) uvBuffer->unmap();
        indexBuffer.commit(indexData);
        primitiveStride = triSize;
        return MHWRender::MGeometry::kPatch;
    }

    if (positionBuffer) positionBuffer->unmap();
    if (uvBuffer) uvBuffer->unmap();
    return MHWRender::MGeometry::kInvalidPrimitive;
}

// This is the primitive generator creation function registered with the DrawRegistry.
// Used to initialize a custom primitive generator.
MHWRender::MPxIndexBufferMutator* CrackFreePrimitiveGenerator::createCrackFreePrimitiveGenerator18()
{
    return new CrackFreePrimitiveGenerator(true /*addAdjacentEdges*/, true /*addDominantEdges*/, true /*addDominantPosition*/);
}

MHWRender::MPxIndexBufferMutator* CrackFreePrimitiveGenerator::createCrackFreePrimitiveGenerator9()
{
    return new CrackFreePrimitiveGenerator(true /*addAdjacentEdges*/, false /*addDominantEdges*/, false /*addDominantPosition*/);
}