[21] Mesh法线的生成算法

 // 生成顶点法线
 bool                        YfCalculateVertexNormal
 (
     void*                   pNormalsBuffer,
     Yuint                   normalStriding,
     Yuint                   normalPos,
     const void*             pVerticesBuffer,
     Yuint                   vertexNum,
     Yuint                   vertexStriding,
     Yuint                   vertexPos,
     void*                   pIndicesBuffer,
     Yuint                   trianglesNum,
     YeIndexType             indexType,
     Yuint                   indexStriding,
     Yuint                   indexPos
 )
 {
     if (!pNormalsBuffer || !pVerticesBuffer || !pIndicesBuffer ||
         vertexNum <  || trianglesNum < )
     {
         return false;
     }

     char* vertexPtr = (char*)pVerticesBuffer + vertexPos;
     char* normalPtr = (char*)pNormalsBuffer + normalPos;
     char* indexPtr  = (char*)pIndicesBuffer + indexPos;

     const YsVector* curVertexPtr[];
     YsVector* curNormalPtr[];
     Yuint nOffset = ;
     YsVector vSub_1;
     YsVector vSub_2;
     YsVector vCross;

     for (Yuint i = ; i < vertexNum; i++)
     {
         curNormalPtr[] = (YsVector*)(normalPtr + i * normalStriding);
         curNormalPtr[]->SetZero();
     }

     if (indexType == YE_INDEX_16_BIT)
     {
         YsTriIndex16* triIndexPtr = NULL;
         for (Yuint i = ; i < trianglesNum; i++)
         {
             triIndexPtr = (YsTriIndex16*)(indexPtr + i * indexStriding);
             curVertexPtr[] = (YsVector*)(vertexPtr + triIndexPtr->index0 * vertexStriding);
             curVertexPtr[] = (YsVector*)(vertexPtr + triIndexPtr->index1 * vertexStriding);
             curVertexPtr[] = (YsVector*)(vertexPtr + triIndexPtr->index2 * vertexStriding);
             curNormalPtr[] = (YsVector*)(normalPtr + triIndexPtr->index0 * normalStriding);
             curNormalPtr[] = (YsVector*)(normalPtr + triIndexPtr->index1 * normalStriding);
             curNormalPtr[] = (YsVector*)(normalPtr + triIndexPtr->index2 * normalStriding);

             vSub_1 = *curVertexPtr[] - *curVertexPtr[];
             vSub_2 = *curVertexPtr[] - *curVertexPtr[];
             YfVector3Cross(vCross, vSub_1, vSub_2);

             for (Yuint j = ; j < ; j++)
             {
                 curNormalPtr[j]->x += vCross.x;
                 curNormalPtr[j]->y += vCross.y;
                 curNormalPtr[j]->z += vCross.z;
             }
         }
     }
     else
     {
         YsTriIndex32* triIndexPtr = NULL;
         for (Yuint i = ; i < trianglesNum; i++)
         {
             triIndexPtr = (YsTriIndex32*)(indexPtr + i * indexStriding);
             curVertexPtr[] = (YsVector*)(vertexPtr + triIndexPtr->index0 * vertexStriding);
             curVertexPtr[] = (YsVector*)(vertexPtr + triIndexPtr->index1 * vertexStriding);
             curVertexPtr[] = (YsVector*)(vertexPtr + triIndexPtr->index2 * vertexStriding);
             curNormalPtr[] = (YsVector*)(normalPtr + triIndexPtr->index0 * normalStriding);
             curNormalPtr[] = (YsVector*)(normalPtr + triIndexPtr->index1 * normalStriding);
             curNormalPtr[] = (YsVector*)(normalPtr + triIndexPtr->index2 * normalStriding);

             vSub_1 = *curVertexPtr[] - *curVertexPtr[];
             vSub_2 = *curVertexPtr[] - *curVertexPtr[];
             YfVector3Cross(vCross, vSub_1, vSub_2);

             for (Yuint j = ; j < ; j++)
             {
                 curNormalPtr[j]->x += vCross.x;
                 curNormalPtr[j]->y += vCross.y;
                 curNormalPtr[j]->z += vCross.z;
             }
         }
     }

     for (Yuint i = ; i < vertexNum; i++)
     {
         curNormalPtr[] = (YsVector*)(normalPtr + i * normalStriding);
         curNormalPtr[]->Normalize();
     }

     return true;
 }