[16] 螺旋面(Spire)图形的生成算法

顶点数据的生成

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

     Yuint numVertices  =  + stacks * ;
     //Yuint numTriangles = stacks * 2;

     char* vertexPtr = (char*)pVerticesBuffer + vertexPos;
     YsVector3* curVertexPtr = NULL;
     Yuint nOffset = ;

     Yreal originOffsetY = 0.0f;
     if (originPose == YE_ORIGIN_POSE_TOP)
     {
         originOffsetY = -height;
     }
     else if (originPose == YE_ORIGIN_POSE_CENTER)
     {
         originOffsetY = -height * 0.5f;
     }

     Yreal fAngle = YD_REAL_TWAIN_PI / slices;

     Yreal angleXZ;
     Yreal posX, posZ;
     for (Yuint i = ; i <= stacks; i++)
     {
         angleXZ = i * fAngle;
         posX = yf_sin(angleXZ);
         posZ = yf_cos(angleXZ);
         nOffset = i *  * vertexStriding; 

         curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
         curVertexPtr->x = assistRadius * posX;
         curVertexPtr->y = height * i * 1.0f / stacks + originOffsetY;
         curVertexPtr->z = assistRadius * posZ;

         nOffset += vertexStriding;  

         curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
         curVertexPtr->x = radius * posX;
         curVertexPtr->y = height * i * 1.0f / stacks + originOffsetY;
         curVertexPtr->z = radius * posZ;
     }

     return true;
 }

三角形索引数据的生成

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

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

     // 索引赋值
     char* indexPtr = (char*)pTriIndicesBuffer + indexPos;
     Yuint nOffset = ;
     if (indexType == YE_INDEX_16_BIT)
     {
         YsTriIndex16* triIndexPtr = NULL;
         for (Yuint i = ; i < stacks; i++)
         {
             nOffset =  * i * indexStriding;
             triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
             triIndexPtr->index0 = i*;
             triIndexPtr->index1 = i* + ;
             triIndexPtr->index2 = i* + ;

             nOffset += indexStriding;
             triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
             triIndexPtr->index0 = i*;
             triIndexPtr->index1 = i* + ;
             triIndexPtr->index2 = i* + ;
         }
     }
     else
     {
         YsTriIndex32* triIndexPtr = NULL;
         for (Yuint i = ; i < stacks; i++)
         {
             nOffset =  * i * indexStriding;
             triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
             triIndexPtr->index0 = i*;
             triIndexPtr->index1 = i* + ;
             triIndexPtr->index2 = i* + ;

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

     return true;
 } 

线框索引数据的生成

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

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

     // 索引赋值
     char* indexPtr = (char*)pWireIndicesBuffer + indexPos;
     Yuint nOffset = ;
     if (indexType == YE_INDEX_16_BIT)
     {
         YsLineIndex16* lineIndexPtr = NULL;
         for (Yuint i = ; i < stacks; i++)
         {
             nOffset = (i * ) * indexStriding;
             lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
             lineIndexPtr->index0 = i * ;
             lineIndexPtr->index1 = i *  + ;

             nOffset += indexStriding;
             lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
             lineIndexPtr->index0 = i *  + ;
             lineIndexPtr->index1 = i * ;

             nOffset += indexStriding;
             lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
             lineIndexPtr->index0 = i *  + ;
             lineIndexPtr->index1 = i *  + ;
         }

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

             nOffset += indexStriding;
             lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
             lineIndexPtr->index0 = i *  + ;
             lineIndexPtr->index1 = i * ;

             nOffset += indexStriding;
             lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
             lineIndexPtr->index0 = i *  + ;
             lineIndexPtr->index1 = i *  + ;
         }

         nOffset = (stacks * ) * indexStriding;
         lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
         lineIndexPtr->index0 = stacks * ;
         lineIndexPtr->index1 = stacks *  + ;
     }

     return true;
 }