error C2662: CObject::getFacetIndicesAt' : cannot convert 'this' pointer from 'const hiveRayTracing::CObject' to 'hiveRayTracing::CO（c++ const this ）

class CObject
    {
        friend class CPlyLoader;
    public:
        CObject::CObject() : m_pMaterial(NULL) {}
        CObject::~CObject() 
        {
            m_Vertex.clear();
            m_VertexNormal.clear();
            m_FacetIndices.clear();
            m_FacetNormal.clear();
        }

        void setMaterial(const CMaterial* pMaterial)  {m_pMaterial  = pMaterial;}

        Point3f getVertexAt(unsigned int vIndex)        {_ASSERT(vIndex < m_Vertex.size()); return m_Vertex.at(vIndex);}
        Point3f getVertexNormalAt(unsigned int vIndex)  {_ASSERT(vIndex < m_VertexNormal.size()); return m_VertexNormal.at(vIndex);}
        Point3i getFacetIndicesAt(unsigned int vIndex)  {_ASSERT(vIndex < m_FacetIndices.size()); return m_FacetIndices.at(vIndex);}
        Point3f getFacetNormalAt(unsigned int vIndex)   {_ASSERT(vIndex < m_Vertex.size()); return m_FacetNormal.at(vIndex);}
        
     
        const CMaterial*  getMaterial()  const  {return m_pMaterial;}

    private:
        std::vector<Point3f> m_Vertex;
        std::vector<Point3f> m_VertexNormal;
        std::vector<Point3i> m_FacetIndices;
        std::vector<Point3f> m_FacetNormal;

class CScene
    {
    public:
        CScene();
        ~CScene();

        void loadModel(const std::string vFileName)
        {
            m_pObject = new CObject();
            m_Ply.load(vFileName, m_pObject);
        }
        const CObject* getObject() const          {return m_pObject;}     .............    ｝

然后我在一段代码中调用pObject->getFacetIndicesAt(vLeaf.getElementAt(i))就会出错

void queryLeafNode(const TVertexProperty& vLeaf)
        {
            const CObject* pObject = getObject();//注意这里是 const*  4             CBBox BBox = vLeaf.getNodeInfo().BBox;
            float tMin, tMax;
            if (!BBox.intersectRay(m_CurrentQuery, tMin, tMax)) return;
            m_CurrentQuery.setMint(tMin);
            m_CurrentQuery.setMaxt(tMax);
            
            unsigned int NumElement = vLeaf.getNumElements();
            for (unsigned int i = 0; i < NumElement; ++i)
            {
                Point3i Index = pObject->getFacetIndicesAt(vLeaf.getElementAt(i));
                float t, u, v;
                if (rayIntersectTriangle(pObject->getVertexAt(Index[0]), pObject->getVertexAt(Index[1]), pObject->getVertexAt(Index[2]), 16                                          m_CurrentQuery, u, v, t))
                {
                    if (t > m_QueryResult.curDis) continue;

                    m_QueryResult.intersectPos = m_CurrentQuery.getOrigin() + m_CurrentQuery.getDir() * t;
                    m_QueryResult.curDis = t; 
                    m_QueryResult.u = u;
                    m_QueryResult.v = v;
                    m_QueryResult.triIdx = vLeaf.getElementAt(i);
                }
            }
        }

第15行 error C2662: 'hiveRayTracing::CObject::getFacetIndicesAt' : cannot convert 'this' pointer from 'const hiveRayTracing::CObject' to 'hiveRayTracing::CObject &'

原因在于带“后”const（成员函数后面：getX() const之类的）修饰符的接口会把this指针转化为为const this类型 ，但是getFacetIndicesAt()是非“后带”const修饰的接口。

修改方法：（1）Point3f getVertexAt(unsigned int vIndex)       const {_ASSERT(vIndex < m_Vertex.size()); return m_Vertex.at(vIndex);}

          （2）Point3f getVertexAt(unsigned int vIndex)       {_ASSERT(vIndex < m_Vertex.size()); return std::const_cast<Point3f*>(this)m_Vertex.at(vIndex);}