[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;

 }