geometryOverrideExample2/geometryOverrideExample2.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.
// ==========================================================================
//+

//
// This plug-in shows how to use MPxGeometryOverride to render geometry with Maya shader network.
// It will register a new type of node "geometryOverrideExample2_shape" that will generate 
// the geometry and connect it to a MPxGeometryOverride.
// 
// The GeometryOverrideExample2_shape class derives from MPxSurfaceShape and it is responsible 
// to generate the geometry data (Cube) and also enable the shape to be selectable in
// Viewport 2.0.
//
// The GeometryOverrideExample2 class derives from MPxGeometryOverride and shows how to
// create / update different render items and fill vertex / index buffers to render the geometry 
// of geometryOverrideExample2_shape.
//
//
// To use this plugin run the following mel or python commands once the plugin is loaded
//
//      Mel script:
//          
//          $shapeNodeName = `createNode geometryOverrideExample2_shape`;
//          sets -add initialShadingGroup $shapeNodeName;
//  
//      Python script:
//
//          shapeNodeName = maya.cmds.createNode('geometryOverrideExample2_shape')
//          maya.cmds.sets(shapeNodeName, add = 'initialShadingGroup')
//
//
// Once the mel/python commands are executed, a lambert shader will be attached to the shading group
// of the shape. Of course, you can change the lambert shader to a different one.
//
#include <maya/MFnPlugin.h>
#include <maya/MDrawRegistry.h>
#include "geometryOverrideExample2.h"
#include <maya/MShaderManager.h>
#include <maya/MSelectionMask.h>
#include <maya/MFnDependencyNode.h>
#include <maya/MFloatVector.h>
#include <maya/MGlobal.h>
#include <iostream>

static void instancingChangedCallback(MDagPath& child, MDagPath& parent, void* clientData)
{
    MGlobal::displayWarning("GeometryOverrideExample2 does't support instancing !");
}



//===========================================================================
//
//              geometryOverrideExample2_shape implementation
//
//===========================================================================

MTypeId GeometryOverrideExample2_shape::id = MTypeId(0x8003D);



GeometryOverrideExample2_shape::GeometryOverrideExample2_shape()
{
    const float cubeWidth = 1.0f;
    const float cubeHeight= 1.0f;
    const float cubeDepth = 1.0f;

    //
    // Define the cube's vertices data
    //
    fPositions.emplace_back(-cubeWidth, -cubeHeight, -cubeDepth);
    fPositions.emplace_back(-cubeWidth,  cubeHeight, -cubeDepth);
    fPositions.emplace_back( cubeWidth,  cubeHeight, -cubeDepth);
    fPositions.emplace_back( cubeWidth, -cubeHeight, -cubeDepth);
    fPositions.emplace_back(-cubeWidth, -cubeHeight,  cubeDepth);
    fPositions.emplace_back( cubeWidth, -cubeHeight,  cubeDepth);
    fPositions.emplace_back( cubeWidth,  cubeHeight,  cubeDepth);
    fPositions.emplace_back(-cubeWidth,  cubeHeight,  cubeDepth);
    fPositions.emplace_back(-cubeWidth,  cubeHeight, -cubeDepth);
    fPositions.emplace_back(-cubeWidth,  cubeHeight,  cubeDepth);
    fPositions.emplace_back( cubeWidth,  cubeHeight,  cubeDepth);
    fPositions.emplace_back( cubeWidth,  cubeHeight, -cubeDepth);
    fPositions.emplace_back(-cubeWidth, -cubeHeight, -cubeDepth);
    fPositions.emplace_back( cubeWidth, -cubeHeight, -cubeDepth);
    fPositions.emplace_back( cubeWidth, -cubeHeight,  cubeDepth);
    fPositions.emplace_back(-cubeWidth, -cubeHeight,  cubeDepth);
    fPositions.emplace_back(-cubeWidth, -cubeHeight,  cubeDepth);
    fPositions.emplace_back(-cubeWidth,  cubeHeight,  cubeDepth);
    fPositions.emplace_back(-cubeWidth,  cubeHeight, -cubeDepth);
    fPositions.emplace_back(-cubeWidth, -cubeHeight, -cubeDepth);
    fPositions.emplace_back( cubeWidth, -cubeHeight, -cubeDepth);
    fPositions.emplace_back( cubeWidth,  cubeHeight, -cubeDepth);
    fPositions.emplace_back( cubeWidth,  cubeHeight,  cubeDepth);
    fPositions.emplace_back( cubeWidth, -cubeHeight,  cubeDepth);

    fNormals.emplace_back( 0.0f,  0.0f, -1.0f);
    fNormals.emplace_back( 0.0f,  0.0f, -1.0f);
    fNormals.emplace_back( 0.0f,  0.0f, -1.0f);
    fNormals.emplace_back( 0.0f,  0.0f, -1.0f);
    fNormals.emplace_back( 0.0f,  0.0f,  1.0f);
    fNormals.emplace_back( 0.0f,  0.0f,  1.0f);
    fNormals.emplace_back( 0.0f,  0.0f,  1.0f);
    fNormals.emplace_back( 0.0f,  0.0f,  1.0f);
    fNormals.emplace_back( 0.0f,  1.0f,  0.0f);
    fNormals.emplace_back( 0.0f,  1.0f,  0.0f);
    fNormals.emplace_back( 0.0f,  1.0f,  0.0f);
    fNormals.emplace_back( 0.0f,  1.0f,  0.0f);
    fNormals.emplace_back( 0.0f, -1.0f,  0.0f);
    fNormals.emplace_back( 0.0f, -1.0f,  0.0f);
    fNormals.emplace_back( 0.0f, -1.0f,  0.0f);
    fNormals.emplace_back( 0.0f, -1.0f,  0.0f);
    fNormals.emplace_back(-1.0f,  0.0f,  0.0f);
    fNormals.emplace_back(-1.0f,  0.0f,  0.0f);
    fNormals.emplace_back(-1.0f,  0.0f,  0.0f);
    fNormals.emplace_back(-1.0f,  0.0f,  0.0f);
    fNormals.emplace_back( 1.0f,  0.0f,  0.0f);
    fNormals.emplace_back( 1.0f,  0.0f,  0.0f);
    fNormals.emplace_back( 1.0f,  0.0f,  0.0f);
    fNormals.emplace_back( 1.0f,  0.0f,  0.0f);

    fTangents.emplace_back( 1.0f, 0.0f,  0.0f);
    fTangents.emplace_back( 1.0f, 0.0f,  0.0f);
    fTangents.emplace_back( 1.0f, 0.0f,  0.0f);
    fTangents.emplace_back( 1.0f, 0.0f,  0.0f);
    fTangents.emplace_back(-1.0f, 0.0f,  0.0f);
    fTangents.emplace_back(-1.0f, 0.0f,  0.0f);
    fTangents.emplace_back(-1.0f, 0.0f,  0.0f);
    fTangents.emplace_back(-1.0f, 0.0f,  0.0f);
    fTangents.emplace_back( 1.0f, 0.0f,  0.0f);
    fTangents.emplace_back( 1.0f, 0.0f,  0.0f);
    fTangents.emplace_back( 1.0f, 0.0f,  0.0f);
    fTangents.emplace_back( 1.0f, 0.0f,  0.0f);
    fTangents.emplace_back(-1.0f, 0.0f,  0.0f);
    fTangents.emplace_back(-1.0f, 0.0f,  0.0f);
    fTangents.emplace_back(-1.0f, 0.0f,  0.0f);
    fTangents.emplace_back(-1.0f, 0.0f,  0.0f);
    fTangents.emplace_back( 0.0f, 0.0f, -1.0f);
    fTangents.emplace_back( 0.0f, 0.0f, -1.0f);
    fTangents.emplace_back( 0.0f, 0.0f, -1.0f);
    fTangents.emplace_back( 0.0f, 0.0f, -1.0f);
    fTangents.emplace_back( 0.0f, 0.0f,  1.0f);
    fTangents.emplace_back( 0.0f, 0.0f,  1.0f);
    fTangents.emplace_back( 0.0f, 0.0f,  1.0f);
    fTangents.emplace_back( 0.0f, 0.0f,  1.0f);

    fTextureCoords.emplace_back(0.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 1.0f);
    fTextureCoords.emplace_back(1.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 0.0f);
    fTextureCoords.emplace_back(0.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 1.0f);
    fTextureCoords.emplace_back(1.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 0.0f);
    fTextureCoords.emplace_back(0.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 1.0f);
    fTextureCoords.emplace_back(0.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 0.0f);
    fTextureCoords.emplace_back(1.0f, 1.0f);

    fBiTangents.resize(24);
    for (int i = 0; i < 24; i++) 
    {
        // cross product
        MFloatVector biTangents = MFloatVector(fNormals[i].x,  fNormals[i].y,  fNormals[i]. z) ^ 
                                  MFloatVector(fTangents[i].x, fTangents[i].y, fTangents[i].z);
        fBiTangents[i].x = biTangents.x;
        fBiTangents[i].y = biTangents.y;
        fBiTangents[i].z = biTangents.z;
    }

    fShadedIndices =
    {
        12, 13, 14, 12, 14, 15, // bottom
         8,  9, 10,  8, 10, 11, // top
        16, 17, 18, 16, 18, 19, // left
        20, 21, 22, 20, 22, 23, // right
         4,  5,  6,  4,  6,  7, // back
         0,  1,  2,  0,  2,  3, // front
    };

    fWireFrameIndices =
    {
        0, 1, 1, 2, 2, 3, 3, 0, // bottom
        4, 5, 5, 6, 6, 7, 7, 4, // top
        0, 4, 3, 5, 1, 7, 2, 6, // left / right
    };
}



GeometryOverrideExample2_shape::~GeometryOverrideExample2_shape()
{
    MMessage::removeCallback(mInstanceAddedCallbackId);
}



//  ============================================================
//
//  When instances of this node are created internally, the MObject associated
//  with the instance is not created until after the constructor of this class
//  is called. This means that no member functions of MPxSurfaceShape can
//  be called in the constructor.
//  The postConstructor solves this problem. Maya will call this function
//  after the internal object has been created.
//  As a general rule do all of your initialization in the postConstructor.
//
//  Note : For more information, see MPxSurfaceShape::postConstructor()
//
//  ============================================================
void GeometryOverrideExample2_shape::postConstructor()
{
    // This call allows the shape to have shading groups assigned
    setRenderable(true);


    //
    // Add a callback that will be called when instance are added.
    //
    MDagPath path;
    MDagPath::getAPathTo(thisMObject(), path);
    mInstanceAddedCallbackId = MDagMessage::addInstanceAddedDagPathCallback(const_cast<MDagPath&>(path), &instancingChangedCallback);
}


//  ============================================================
//
//  This method is overriden to support interactive object selection in Viewport 2.0
//
//  Returns The selection mask of the shaper.
//
//  Note : For more information, see MPxSurfaceShape::getShapeSelectionMask()
//
//  ============================================================
MSelectionMask  GeometryOverrideExample2_shape::getShapeSelectionMask() const
{
    MSelectionMask::SelectionType selType = MSelectionMask::kSelectMeshes;
    return MSelectionMask(selType);
}


//  ============================================================
//
//  Returns the bounding box for this object.
//  It is a good idea not to recompute here as this funcion is called often.
//
//  Note : This function is only called if MPxSurfaceShape::isBounded() return true.
//         For more information, see MPxSurfaceShape::boundingBox()
//
//  ============================================================
MBoundingBox GeometryOverrideExample2_shape::boundingBox() const
{
    MPoint corner1Point(fPositions[0].x, fPositions[0].y, fPositions[0].z); // back-left-bottom vertex position
    MPoint corner2Point(fPositions[6].x, fPositions[6].y, fPositions[6].z); // front-right-top  vertex position

    return MBoundingBox(corner1Point, corner2Point);
}




//===========================================================================
//
//              GeometryOverrideExample2 implementation
//
//===========================================================================

const char* GeometryOverrideExample2::sActiveWireframeRenderItemName = "GeometryOverrideExample2_ActiveWireframe";
const char* GeometryOverrideExample2::sDormantWireframeRenderItemName = "GeometryOverrideExample2_DormantWireframe";
const char* GeometryOverrideExample2::sShadedRenderItemName = "GeometryOverrideExample2_shaded";


GeometryOverrideExample2::GeometryOverrideExample2(const MObject& obj)
    : MHWRender::MPxGeometryOverride(obj)
{
    // get the real mesh object from the MObject
    MStatus status;
    MFnDependencyNode node(obj, &status);
    if (status)
    {
        fMesh = dynamic_cast<GeometryOverrideExample2_shape*>(node.userNode());
    }
}



GeometryOverrideExample2::~GeometryOverrideExample2()
{

}


//  ============================================================
//
//  This function return draw API that is supported by this plugin.
//
//  Note : For more information, see MPxGeometryOverride::supportedDrawAPIs()
// 
//  ============================================================
MHWRender::DrawAPI GeometryOverrideExample2::supportedDrawAPIs() const
{
    return  (MHWRender::kOpenGL | MHWRender::kDirectX11 | MHWRender::kOpenGLCoreProfile);
}



//  ============================================================
//
//  Perform any work required to translate the geometry data that needs to get
//  information from the dependency graph.This should be the only place that
//  dependency graph evaluation occurs.Any data retrieved should be cached for
//  later stages.
//
//  Note : For more information, see MPxGeometryOverride::updateDG()
//
//  ============================================================
void GeometryOverrideExample2::updateDG()
{
    // In this example, there is nothing to do here
}



//  ============================================================
//
//  This method is called once during each draw-preparation phase.  If this method returns true 
//  then the associated DAG object will have a chance to update its render geometry this frame.
//  (Maya will call populateGeometry())
//
//  Note : For more information, see MPxGeometryOverride::requiresGeometryUpdate()
//
//  ============================================================
bool GeometryOverrideExample2::requiresGeometryUpdate() const
{
    // In this example, we always return false because the node doesn't have 
    // attributes that affect the geometry.
    return false;
}

//  ============================================================
//
//  If this method returns true then the MPxGeometryOverride will be considered
//  for Evaluation Manager Parallel Update.
//
//  Note : For more information, see MPxGeometryOverride::supportsEvaluationManagerParallelUpdate()
//
//  ============================================================
bool GeometryOverrideExample2::supportsEvaluationManagerParallelUpdate() const
{
    return true;
}



//  ============================================================
//
//  This method is called for each instance of the associated DAG object whenever 
//  the object changes and receive the path to the instance and the current list 
//  of render items associated with that instance. Implementations of this method 
//  may add, remove or modify items in the list. As an alternative this method 
//  can enable or disable items that must be used or not based on some properties.
//  
//  A render item represents a single renderable entity and contain many properties 
//  to let the Viewport 2.0 to know how to render the entity. By example, A render 
//  item contain a name, a type, the geometry primitive type, a set of geometry 
//  buffers and a shader instance. 
//  
//  In this example, this functions will create 2 render items to render the object's 
//  geometry in wireframe mode. The first render item will be use to display the object 
//  in wireframe with a single color only when the Viewport 2.0 is in wireframe mode. 
//  The second render item will be use to render the object with a single color in 
//  wireframe only when the object is selected independing of the Viewport 2.0 display 
//  mode. Both wireframe render item will be enable or disable depending of the object 
//  selection state. 
//  
//  This example will not create a render item to display the geometry in shaded or 
//  textured mode because Maya will do it when a material / shader will be assigned 
//  to the object. This render item will be added in the list and can be edited 
//  if desired. If no material is assigned, the object will not be visible in 
//  Viewport 2.0 except if the node is selected in the outliner. In this situation,
//  only the edges of the object will be displayed because we are creating
//  a wireframe render item that will be used when the object is selected.
//
//  Note : For more information, see MPxGeometryOverride::updateRenderItems()
//
//  ============================================================
void GeometryOverrideExample2::updateRenderItems(const MDagPath& path, MHWRender::MRenderItemList& renderItems)
{
    if (!path.isValid())
        return;


    MRenderer* renderer = MRenderer::theRenderer();
    if (!renderer)
        return;

    const MShaderManager* shaderManager = renderer->getShaderManager();
    if (!shaderManager)
        return;


    // Get the inherited DAG display properties.
    auto wireframeColor = MHWRender::MGeometryUtilities::wireframeColor(path);
    auto displayStatus         = MHWRender::MGeometryUtilities::displayStatus(path);

    // Update the wireframe render item used when the object will be selected
    bool isWireFrameRenderItemEnabled = displayStatus == MHWRender::kLead || displayStatus == MHWRender::kActive;
    updateWireframeItems(sActiveWireframeRenderItemName,
        MHWRender::MGeometry::kAll,
        MHWRender::MRenderItem::sSelectionDepthPriority,
        wireframeColor,
        isWireFrameRenderItemEnabled,
        renderItems,
        *shaderManager);


    // Update the wireframe render item used when the object will not be selected
    isWireFrameRenderItemEnabled = displayStatus == MHWRender::kDormant;
    updateWireframeItems(sDormantWireframeRenderItemName,
        MHWRender::MGeometry::kWireframe,
        MHWRender::MRenderItem::sDormantWireDepthPriority,
        wireframeColor,
        isWireFrameRenderItemEnabled,
        renderItems,
        *shaderManager);
}



//  ============================================================
//
//  Fill in data and index streams based on the requirements passed in.
//  Associate indexing with the render items passed in.
//
//  Note : For more information, see MPxGeometryOverride::populateGeometry()
//
//  ============================================================
void GeometryOverrideExample2::populateGeometry(const MHWRender::MGeometryRequirements& requirements, const MHWRender::MRenderItemList& renderItems, MHWRender::MGeometry& data)
{
    if (!fMesh)
        return;

    const MVertexBufferDescriptorList&  vertexBufferDescriptorList = requirements.vertexRequirements();
    for (int i = 0; i < vertexBufferDescriptorList.length(); i++)
    {
        MVertexBufferDescriptor desc{};
        if (!vertexBufferDescriptorList.getDescriptor(i, desc))
            continue;

        std::cout << desc.semanticName().asChar() << std::endl;

        switch (desc.semantic())
        {
        case MGeometry::kPosition:
        {
            //
            // Create and fill the vertex position buffer
            //
            MHWRender::MVertexBuffer* positionBuffer = data.createVertexBuffer(desc);

            if (positionBuffer)
            {
                GeometryOverrideExample2_shape::Float3Array positions = fMesh->getPositions();

                void* buffer = positionBuffer->acquire(positions.size(), true /*writeOnly */);
                if (buffer)
                {
                    const std::size_t bufferSizeInByte =
                        sizeof(GeometryOverrideExample2_shape::Float3Array::value_type) * positions.size();

                    memcpy(buffer, positions.data(), bufferSizeInByte);

                    // Transfer from CPU to GPU memory.
                    positionBuffer->commit(buffer);
                }
            }
        }
        break;
        case MGeometry::kNormal:
        {
            //
            // Create and fill the vertex normal buffer
            //
            MHWRender::MVertexBuffer* normalsBuffer = data.createVertexBuffer(desc);

            if (normalsBuffer)
            {
                GeometryOverrideExample2_shape::Float3Array normals = fMesh->getNormals();

                void* buffer = normalsBuffer->acquire(normals.size(), true /*writeOnly*/);
                if (buffer)
                {
                    const std::size_t bufferSizeInByte =
                        sizeof(GeometryOverrideExample2_shape::Float3Array::value_type) * normals.size();

                    memcpy(buffer, normals.data(), bufferSizeInByte);

                    // Transfer from CPU to GPU memory.
                    normalsBuffer->commit(buffer);
                }
            }
        }
        break;
        case MGeometry::kTangent:
        {
            MHWRender::MVertexBuffer* tangentBuffer = data.createVertexBuffer(desc);

            if (tangentBuffer)
            {
                GeometryOverrideExample2_shape::Float3Array tangents = fMesh->getTangents();

                void* buffer = tangentBuffer->acquire(tangents.size(), true /*writeOnly*/);
                if (buffer)
                {
                    const std::size_t bufferSizeInByte =
                        sizeof(GeometryOverrideExample2_shape::Float3Array::value_type) * tangents.size();

                    memcpy(buffer, tangents.data(), bufferSizeInByte);

                    // Transfer from CPU to GPU memory.
                    tangentBuffer->commit(buffer);
                }
            }
        }
            break;
        case MGeometry::kBitangent:
        {
            MHWRender::MVertexBuffer* tangentBuffer = data.createVertexBuffer(desc);

            if (tangentBuffer)
            {
                GeometryOverrideExample2_shape::Float3Array tangents = fMesh->getBiTangents();

                void* buffer = tangentBuffer->acquire(tangents.size(), true /*writeOnly*/);
                if (buffer)
                {
                    const std::size_t bufferSizeInByte =
                        sizeof(GeometryOverrideExample2_shape::Float3Array::value_type) * tangents.size();

                    memcpy(buffer, tangents.data(), bufferSizeInByte);

                    // Transfer from CPU to GPU memory.
                    tangentBuffer->commit(buffer);
                }
            }
        }
            break;
        case MGeometry::kTexture:
        {
            //
            // Create and fill the vertex texture coords buffer
            //
            MHWRender::MVertexBuffer* texCoordsBuffer = data.createVertexBuffer(desc);

            if (texCoordsBuffer)
            {
                GeometryOverrideExample2_shape::Float2Array texCoords = fMesh->getTexCoords();

                void* buffer = texCoordsBuffer->acquire(texCoords.size(), true /*writeOnly*/);
                if (buffer)
                {
                    const std::size_t bufferSizeInByte =
                        sizeof(GeometryOverrideExample2_shape::Float2Array::value_type) * texCoords.size();

                    memcpy(buffer, texCoords.data(), bufferSizeInByte);

                    // Transfer from CPU to GPU memory.
                    texCoordsBuffer->commit(buffer);
                }
            }
        }
        break;
        case MGeometry::kColor:
        case MGeometry::kTangentWithSign:
        case MGeometry::kInvalidSemantic:   // avoid compiling error
            //
            // In this example, we don't need to used those vertex informantions.
            //
            break;
        }
    }


    //   Update indexing data for all appropriate render items
    const int numItems = renderItems.length();
    for (int i = 0; i < numItems; i++)
    {
        const MHWRender::MRenderItem* item = renderItems.itemAt(i);
        if (!item)
            continue;

        if (item->primitive() == MHWRender::MGeometry::kTriangles)
        {
            //
            // Create and fill the index buffer used to render triangles
            //
            MHWRender::MIndexBuffer* indexBuffer = data.createIndexBuffer(MHWRender::MGeometry::kUnsignedInt32);
            if (indexBuffer)
            {
                GeometryOverrideExample2_shape::IndexList indices = fMesh->getShadedIndices();
                void* buffer = indexBuffer->acquire(indices.size(), true /*writeOnly*/);
                if (buffer)
                {
                    const std::size_t bufferSizeInByte =
                        sizeof(GeometryOverrideExample2_shape::IndexList::value_type) * indices.size();

                    memcpy(buffer, indices.data(), bufferSizeInByte);

                    // Transfer from CPU to GPU memory.
                    indexBuffer->commit(buffer);

                    // Associate index buffer with render item
                    item->associateWithIndexBuffer(indexBuffer);
                }
            }
        }
        else if (item->primitive() == MHWRender::MGeometry::kLines)
        {
            //
            // Create and fill the index buffer used to render lines (Wireframe)
            //
            MHWRender::MIndexBuffer* indexBuffer = data.createIndexBuffer(MHWRender::MGeometry::kUnsignedInt32);
            if (indexBuffer)
            {
                GeometryOverrideExample2_shape::IndexList indices = fMesh->getWireFrameIndices();

                void* buffer = indexBuffer->acquire(indices.size(), true /*writeOnly*/);
                if (buffer)
                {
                    const std::size_t bufferSizeInByte =
                        sizeof(GeometryOverrideExample2_shape::IndexList::value_type) * indices.size();

                    memcpy(buffer, indices.data(), bufferSizeInByte);

                    // Transfer from CPU to GPU memory.
                    indexBuffer->commit(buffer);

                    // Associate index buffer with render item
                    item->associateWithIndexBuffer(indexBuffer);
                }
            }
        }
    }
}


//  ============================================================
//
//  Clean up any cached data stored from the updateDG() phase.
//
//  Note : For more information, see MPxGeometryOverride::cleanUp()
//
//  ============================================================
void GeometryOverrideExample2::cleanUp()
{
    // Nothing here because the plugin doesn't keep any temporary data.
}



//  ============================================================
//
//  Update the wireframe render item named 'renderItemName' or create it
//  if it doesn't exists.
//
//  Note : Arguments drawMode and depthPriority are only used for creation of 
//         the render item.
//
//  ============================================================
void GeometryOverrideExample2::updateWireframeItems(const char* renderItemName, MGeometry::DrawMode drawMode,
    unsigned int depthPriority, MColor color, bool isEnable,
    MHWRender::MRenderItemList& renderItemList,
    const MHWRender::MShaderManager& shaderManager)
{

    MHWRender::MRenderItem* renderItem = nullptr;

    // Try to find the active wireframe render item.
    // If the returning index is smaller than 0, that means 
    // the render item does't exists yet. So, create it.
    auto renderItemIndex = renderItemList.indexOf(renderItemName);
    if (renderItemIndex < 0)
    {
        // Create the new render item with the given name.
        // We designate this item as a UI "decoration" and will not be
        // involved in rendering aspects such as casting shadows
        // The "topology" for the render item is a line list.
        renderItem = MHWRender::MRenderItem::Create(renderItemName,
            MHWRender::MRenderItem::DecorationItem,
            MHWRender::MGeometry::kLines);

        // We want this render item to show up when in all mode ( Wireframe, Shaded, Textured and BoundingBox)
        renderItem->setDrawMode(drawMode);

        // Set selection priority: on top of everything
        renderItem->depthPriority(depthPriority);

        // Get an instance of a 3dSolidShader from the shader manager.
        // The shader tells the graphics hardware how to draw the geometry. 
        // The MShaderInstance is a reference to a shader along with the values for the shader parameters.
        MShaderInstance* shader = shaderManager.getStockShader(MShaderManager::k3dSolidShader);
        if (shader)
        {
            // Assign the shader to the render item. This adds a reference to that
            // shader.
            renderItem->setShader(shader);

            // Once assigned, no need to hold on to shader instance
            shaderManager.releaseShader(shader);
        }

        // The item must be added to the persistent list to be considered
        // for update / rendering
        renderItemList.append(renderItem);
    }
    else
    {
        renderItem = renderItemList.itemAt(renderItemIndex);
    }

    if (renderItem)
    {
        MHWRender::MShaderInstance* shader = renderItem->getShader();
        if (shader)
        {
            // Set the shader color parameter
            shader->setParameter("solidColor", &color.r);
        }

        renderItem->enable(isEnable);
    }
}



//===========================================================================
//
//              initialize / uninitialize plugin
//
//===========================================================================



namespace
{
    MString sDrawDbClassification("drawdb/geometry/geometryOverrideExample2");
    MString sDrawRegistrantId("geometryOverrideExample2Plugin");
}




MStatus initializePlugin(MObject obj)
{
    MFnPlugin plugin(obj, PLUGIN_COMPANY, "3.0", "Any");
    MStatus status;

    status = plugin.registerShape("geometryOverrideExample2_shape",             // the name of the new type of user defined shape node
        GeometryOverrideExample2_shape::id,             // a unique id that identifies this node
        &GeometryOverrideExample2_shape::creator,       // function that will return a pointer to a new instance of the class 
                                                        // (derived from MPxSurfaceNode) that implements the new shape node type
        &GeometryOverrideExample2_shape::initialize,    // function that will initialize all the attributes of the new shape node type
        nullptr,
        &sDrawDbClassification);
    if (!status)
    {
        std::cerr << "Failed to register geometryOverrideExample2_shape." << std::endl;
        return status;
    }


    status = MHWRender::MDrawRegistry::registerGeometryOverrideCreator(sDrawDbClassification,
        sDrawRegistrantId,
        GeometryOverrideExample2::Creator);
    if (!status)
    {
        std::cerr << "Failed to register Viewport 2.0 geometry override." << std::endl;
        return status;
    }

    return status;

}

MStatus uninitializePlugin(MObject obj)
{
    MFnPlugin plugin(obj);
    MStatus status;

    status = MHWRender::MDrawRegistry::deregisterGeometryOverrideCreator(sDrawDbClassification, sDrawRegistrantId);
    if (!status)
    {
        std::cerr << "Failed to deregister geometry override." << std::endl;
    }

    status = plugin.deregisterNode(GeometryOverrideExample2_shape::id);
    if (!status)
    {
        std::cerr << "Failed to deregister GeometryOverrideExample2_shape." << std::endl;
    }

    return status;
}