[9] 圆环(Ring)图形的生成算法

顶点数据的生成

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

     Yuint numVertices  = slices * stacks;
     Yuint numTriangles = slices * stacks * ;

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

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

     Yreal angle, s, c;
     YsVector3* initVerticesPtr = new YsVector3[slices + ];
     for (Yuint j = ; j < slices; j++)
     {
         angle = YD_REAL_TWAIN_PI * j / slices;
         s = yf_sin(angle);
         c = yf_cos(angle);
         initVerticesPtr[j].x = radius + assistRadius*s;
         initVerticesPtr[j].y = halfHeight*c + originOffsetY;
         initVerticesPtr[j].z = 0.0f;
     }

     for (Yuint i = ; i < stacks; i++)
     {
         angle = YD_REAL_TWAIN_PI * i / stacks;
         s = yf_sin(angle);
         c = yf_cos(angle);

         for (Yuint j = ; j < slices; j++)
         {
             nOffset = (i * slices + j) * vertexStriding;
             curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
             curVertexPtr->x = initVerticesPtr[j].x * s;
             curVertexPtr->y = initVerticesPtr[j].y;
             curVertexPtr->z = initVerticesPtr[j].x * c;
         }
     }

     YD_SAFE_DELETE_ARRAY(initVerticesPtr);

     return true;
 }     

三角形索引数据的生成

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

     Yuint numVertices  = slices * stacks;
     Yuint numTriangles = slices * 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++)
         {
             for (Yuint j = ; j < slices; j++)
             {
                 nOffset = (i*slices + j)* * indexStriding;
                 triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
                 triIndexPtr->index0 = slices * i + j;
                 triIndexPtr->index1 = slices * i + (j + )%slices;
                 triIndexPtr->index2 = slices * ((i + ) % stacks) + j;

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

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

     return true;
 }   

线框索引数据的生成

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

     Yuint numVertices = slices * stacks;
     Yuint numLines    = slices * 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++)
         {
             for (Yuint j = ; j < slices; j++)
             {
                 nOffset = (i*slices + j) *  * indexStriding;
                 lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
                 lineIndexPtr->index0 = slices * i + j;
                 lineIndexPtr->index1 = slices * i + (j + )%slices;

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

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

     return true;
 }