[1] 平面(Plane)图形的生成算法

顶点数据的生成

 bool                        YfBuildPlaneVertices
 (
     Yreal                   width,
     Yreal                   length,
     Yreal                   height,
     Yuint                   slices,
     Yuint                   stacks,
     YeOriginPose            originPose,
     Yuint                   vertexStriding,
     Yuint                   vertexPos,
     void*                   pVerticesBuffer
 )
 {
     if (slices <  || stacks <  || !pVerticesBuffer)
     {
         return false;
     }

     // 顶点赋值
     char* vertexPtr = (char*)pVerticesBuffer + vertexPos;
     YsVector3* curVertexPtr = NULL;
     Yuint nOffset = ;

     Yreal xStep = width  / slices;
     Yreal zStep = length / stacks;
     YsVector3 vOrigin;
     if (originPose == YE_ORIGIN_POSE_CENTER)
     {
         vOrigin.x = -width * 0.5f;
         vOrigin.z = -length * 0.5f;
     }

     for (Yuint j = ; j < stacks; j++)             // Z方向
     {
         for (Yuint i = ; i < slices; i++)         // X方向
         {
             nOffset =  (j*slices + i) * vertexStriding;
             curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
             curVertexPtr->x = vOrigin.x + i*xStep;
             curVertexPtr->y = height;
             curVertexPtr->z = vOrigin.z + j*zStep;
         }
     }

     return true;
 }

三角形索引数据的生成

 bool                        YfBuildPlaneTriIndices
 (
     Yuint                   slices,
     Yuint                   stacks,
     YeIndexType             indexType,
     Yuint                   indexStriding,
     Yuint                   indexPos,
     void*                   pTriIndicesBuffer
 )
 {
     if (slices <  || stacks <  || !pTriIndicesBuffer)
     {
         return false;
     }

     Yuint numVertices  = slices * stacks;
     if (indexType == YE_INDEX_16_BIT &&
         numVertices > YD_MAX_UNSIGNED_INT16)
     {
         return false;
     }

     Yuint numTriangles = (slices - ) * (stacks - ) * ;

     char* indexPtr = (char*)pTriIndicesBuffer + indexPos;
     Yuint nOffset = ;

     if (indexType == YE_INDEX_16_BIT)
     {
         YsTriIndex16* triIndexPtr = NULL;

         for (Yuint j = ; j < stacks - ; j++)             // Z方向
         {
             for (Yuint i = ; i < slices - ; i++)         // X方向
             {
                 nOffset = ( * (j*(slices - ) + i)) * indexStriding;
                 triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
                 triIndexPtr->index0 = j*slices + i;
                 triIndexPtr->index1 = (j + )*slices + i + ;
                 triIndexPtr->index2 = j*slices + i + ;

                 nOffset += indexStriding;
                 triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
                 triIndexPtr->index0 = j*slices + i;
                 triIndexPtr->index1 = (j + )*slices + i;
                 triIndexPtr->index2 = (j + )*slices + i + ;
             }
         }
     }
     else
     {
         YsTriIndex32* triIndexPtr = NULL;

         for (Yuint j = ; j < stacks - ; j++)             // Z方向
         {
             for (Yuint i = ; i < slices - ; i++)         // X方向
             {
                 nOffset = ( * (j*(slices - ) + i)) * indexStriding;
                 triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
                 triIndexPtr->index0 = j*slices + i;
                 triIndexPtr->index1 = (j + )*slices + i + ;
                 triIndexPtr->index2 = j*slices + i + ;

                 nOffset += indexStriding;
                 triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
                 triIndexPtr->index0 = j*slices + i;
                 triIndexPtr->index1 = (j + )*slices + i;
                 triIndexPtr->index2 = (j + )*slices + i + ;
             }
         }
     }

     return true;
 }

线框索引数据的生成

 bool                        YfBuildPlaneWireIndices
 (
     Yuint                   slices,
     Yuint                   stacks,
     YeIndexType             indexType,
     Yuint                   indexStriding,
     Yuint                   indexPos,
     void*                   pWireIndicesBuffer
 )
 {
     if (slices <  || stacks <  || !pWireIndicesBuffer)
     {
         return false;
     }

     Yuint numVertices  = slices * stacks;
     if (indexType == YE_INDEX_16_BIT &&
         numVertices > YD_MAX_UNSIGNED_INT16)
     {
         return false;
     }

     Yuint numLines = slices * (stacks - ) +(slices - ) * stacks;

     char* indexPtr = (char*)pWireIndicesBuffer + indexPos;
     Yuint nOffset = ;

     if (indexType == YE_INDEX_16_BIT)
     {
         YsLineIndex16* lineIndexPtr = NULL;

         // 行
         for (Yuint j = ; j < stacks; j++)
         {
             for (Yuint i = ; i < slices - ; i++)
             {
                 nOffset = ((j*(slices - ) + i)) * indexStriding;
                 lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
                 lineIndexPtr->index0 = j*slices + i;
                 lineIndexPtr->index1 = j*slices + i + ;
             }
         }

         // 列
         Yuint half = (slices - ) * stacks;
         for (Yuint i = ; i < slices; i++)
         {
             for (Yuint j = ; j < stacks - ; j++)
             {
                 nOffset = (half + (i*(stacks - ) + j)) * indexStriding;
                 lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
                 lineIndexPtr->index0 = j*slices + i;
                 lineIndexPtr->index1 = (j + )*slices + i;
             }
         }
     }
     else
     {
         YsLineIndex32* lineIndexPtr = NULL;

         // 行
         for (Yuint j = ; j < stacks; j++)
         {
             for (Yuint i = ; i < slices - ; i++)
             {
                 nOffset = ((j*(slices - ) + i)) * indexStriding;
                 lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
                 lineIndexPtr->index0 = j*slices + i;
                 lineIndexPtr->index1 = j*slices + i + ;
             }
         }

         // 列
         Yuint half = (slices - ) * stacks;
         for (Yuint i = ; i < slices; i++)
         {
             for (Yuint j = ; j < stacks - ; j++)
             {
                 nOffset = (half + (i*(stacks - ) + j)) * indexStriding;
                 lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
                 lineIndexPtr->index0 = j*slices + i;
                 lineIndexPtr->index1 = (j + )*slices + i;
             }
         }
     }

     return true;
 }