blindDataShader/blindDataMeshVertexBufferGenerator.cpp

//-
// ==========================================================================
// Copyright 2018 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.
// ==========================================================================
//+
#include "blindDataMeshVertexBufferGenerator.h"
#include <maya/MFnMesh.h>
#include <maya/MIntArray.h>
#include <maya/MItMeshVertex.h>


bool blindDataMeshVertexBufferGenerator::getSourceIndexing(const MObject& object, MComponentDataIndexing& sourceIndexing) const
{
    // get the mesh from the current path
    // if it is not a mesh we do nothing.
    MStatus status;
    MFnMesh mesh(object, &status);
    if (!status) 
        return false;

    MIntArray vertexCount, vertexList;
    mesh.getVertices(vertexCount, vertexList);
    unsigned int vertCount = vertexList.length();

    MUintArray& vertices = sourceIndexing.indices();
    vertices.setLength(vertCount);

    for (unsigned int i = 0; i < vertCount; ++i)
        vertices[i] = (unsigned int)vertexList[i];

    // assign the source indexing
    sourceIndexing.setComponentType(MComponentDataIndexing::kFaceVertex);

    return true;
}



bool blindDataMeshVertexBufferGenerator::getSourceStreams(const MObject& object, MStringArray &sourceStreams) const
{
    return false;
}



void blindDataMeshVertexBufferGenerator::createVertexStream(const MObject& object, MVertexBuffer& vertexBuffer, const MComponentDataIndexing& targetIndexing, const MComponentDataIndexing& sharedIndexing, const MVertexBufferArray& sourceStreams) const
{
    const MVertexBufferDescriptor& descriptor = vertexBuffer.descriptor();
        
    // We are expected 4 floats with the color semantic 
    if ( (descriptor.dataType() != MGeometry::kFloat) || 
         (descriptor.dimension() != 4) || 
         (descriptor.semantic() != MGeometry::kColor))
         return;

    // object should be a mesh
    MStatus status;
    MFnMesh mesh(object, &status);
    if (!status) 
        return;

    const MUintArray& indices = targetIndexing.indices();

    const unsigned int vertexCount = indices.length();
    if (vertexCount <= 0)
        return;

    const unsigned vertexBufferSize = vertexCount * 4 * sizeof(float);
    float* customBuffer = (float*)vertexBuffer.acquire(vertexBufferSize, true /*writeOnly*/);

    if (customBuffer)
    {   
        //
        // Extract the mesh blind data and copy it into the vertex buffer.
        //

        // Constant use to extract the blind data. See blindDataMesh::setMeshBlindData()
        const int blindDataID = 60;

        MItMeshVertex itVertex((MObject&)object);
        for (; !itVertex.isDone(); itVertex.next())
        {
            double red, green, blue = 0;

            int vertexIndex = itVertex.index();

            mesh.getDoubleBlindData(vertexIndex, MFn::kMeshVertComponent, blindDataID, "red", red);
            mesh.getDoubleBlindData(vertexIndex, MFn::kMeshVertComponent, blindDataID, "green", green);
            mesh.getDoubleBlindData(vertexIndex, MFn::kMeshVertComponent, blindDataID, "blue", blue);

            customBuffer[vertexIndex * 4    ] = static_cast<float>(red);
            customBuffer[vertexIndex * 4 + 1] = static_cast<float>(green);
            customBuffer[vertexIndex * 4 + 2] = static_cast<float>(blue);
            customBuffer[vertexIndex * 4 + 3] = 1.0f;
        }
        
        vertexBuffer.commit(customBuffer);
    }
}