• [1] 平面(Plane)图形的生成算法


    顶点数据的生成

     1 bool                        YfBuildPlaneVertices
     2 (
     3     Yreal                   width, 
     4     Yreal                   length, 
     5     Yreal                   height, 
     6     Yuint                   slices, 
     7     Yuint                   stacks, 
     8     YeOriginPose            originPose,     
     9     Yuint                   vertexStriding, 
    10     Yuint                   vertexPos,    
    11     void*                   pVerticesBuffer
    12 )
    13 {
    14     if (slices < 2 || stacks < 2 || !pVerticesBuffer)
    15     {
    16         return false;
    17     }
    18 
    19     // 顶点赋值
    20     char* vertexPtr = (char*)pVerticesBuffer + vertexPos;
    21     YsVector3* curVertexPtr = NULL;
    22     Yuint nOffset = 0;
    23   
    24     Yreal xStep = width  / slices;
    25     Yreal zStep = length / stacks;
    26     YsVector3 vOrigin;
    27     if (originPose == YE_ORIGIN_POSE_CENTER)
    28     {
    29         vOrigin.x = -width * 0.5f;
    30         vOrigin.z = -length * 0.5f;
    31     }
    32 
    33     for (Yuint j = 0; j < stacks; j++)             // Z方向
    34     {
    35         for (Yuint i = 0; i < slices; i++)         // X方向
    36         {
    37             nOffset =  (j*slices + i) * vertexStriding;
    38             curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
    39             curVertexPtr->x = vOrigin.x + i*xStep;
    40             curVertexPtr->y = height;
    41             curVertexPtr->z = vOrigin.z + j*zStep;
    42         }
    43     }
    44 
    45     return true;
    46 }

    三角形索引数据的生成

     1 bool                        YfBuildPlaneTriIndices
     2 (
     3     Yuint                   slices,
     4     Yuint                   stacks, 
     5     YeIndexType             indexType,
     6     Yuint                   indexStriding,  
     7     Yuint                   indexPos,
     8     void*                   pTriIndicesBuffer
     9 )
    10 {
    11     if (slices < 2 || stacks < 2 || !pTriIndicesBuffer)
    12     {
    13         return false;
    14     }
    15 
    16     Yuint numVertices  = slices * stacks;
    17     if (indexType == YE_INDEX_16_BIT && 
    18         numVertices > YD_MAX_UNSIGNED_INT16)
    19     {
    20         return false;
    21     }
    22 
    23     Yuint numTriangles = (slices - 1) * (stacks - 1) * 2;
    24 
    25     char* indexPtr = (char*)pTriIndicesBuffer + indexPos;
    26     Yuint nOffset = 0;
    27 
    28     if (indexType == YE_INDEX_16_BIT)
    29     {
    30         YsTriIndex16* triIndexPtr = NULL;
    31 
    32         for (Yuint j = 0; j < stacks - 1; j++)             // Z方向
    33         {
    34             for (Yuint i = 0; i < slices - 1; i++)         // X方向
    35             {
    36                 nOffset = (2 * (j*(slices - 1) + i)) * indexStriding;
    37                 triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
    38                 triIndexPtr->index0 = j*slices + i;
    39                 triIndexPtr->index1 = (j + 1)*slices + i + 1;
    40                 triIndexPtr->index2 = j*slices + i + 1;
    41 
    42                 nOffset += indexStriding;                
    43                 triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
    44                 triIndexPtr->index0 = j*slices + i;
    45                 triIndexPtr->index1 = (j + 1)*slices + i;
    46                 triIndexPtr->index2 = (j + 1)*slices + i + 1;
    47             }
    48         }
    49     }
    50     else
    51     {
    52         YsTriIndex32* triIndexPtr = NULL;
    53 
    54         for (Yuint j = 0; j < stacks - 1; j++)             // Z方向
    55         {
    56             for (Yuint i = 0; i < slices - 1; i++)         // X方向
    57             {
    58                 nOffset = (2 * (j*(slices - 1) + i)) * indexStriding;
    59                 triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
    60                 triIndexPtr->index0 = j*slices + i;
    61                 triIndexPtr->index1 = (j + 1)*slices + i + 1;
    62                 triIndexPtr->index2 = j*slices + i + 1;
    63 
    64                 nOffset += indexStriding;                
    65                 triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
    66                 triIndexPtr->index0 = j*slices + i;
    67                 triIndexPtr->index1 = (j + 1)*slices + i;
    68                 triIndexPtr->index2 = (j + 1)*slices + i + 1;
    69             }
    70         }
    71     }
    72 
    73     return true;
    74 }

    线框索引数据的生成

     1 bool                        YfBuildPlaneWireIndices
     2 (
     3     Yuint                   slices,
     4     Yuint                   stacks, 
     5     YeIndexType             indexType,
     6     Yuint                   indexStriding,  
     7     Yuint                   indexPos,
     8     void*                   pWireIndicesBuffer
     9 )
    10 {
    11     if (slices < 2 || stacks < 2 || !pWireIndicesBuffer)
    12     {
    13         return false;
    14     }
    15 
    16     Yuint numVertices  = slices * stacks;
    17     if (indexType == YE_INDEX_16_BIT && 
    18         numVertices > YD_MAX_UNSIGNED_INT16)
    19     {
    20         return false;
    21     }
    22 
    23     Yuint numLines = slices * (stacks - 1) +(slices - 1) * stacks;
    24 
    25     char* indexPtr = (char*)pWireIndicesBuffer + indexPos;
    26     Yuint nOffset = 0;
    27 
    28     if (indexType == YE_INDEX_16_BIT)
    29     {
    30         YsLineIndex16* lineIndexPtr = NULL;
    31 
    32         //
    33         for (Yuint j = 0; j < stacks; j++)                 
    34         {
    35             for (Yuint i = 0; i < slices - 1; i++)         
    36             {
    37                 nOffset = ((j*(slices - 1) + i)) * indexStriding;
    38                 lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
    39                 lineIndexPtr->index0 = j*slices + i;
    40                 lineIndexPtr->index1 = j*slices + i + 1;
    41             }
    42         }
    43 
    44         //
    45         Yuint half = (slices - 1) * stacks;
    46         for (Yuint i = 0; i < slices; i++)                 
    47         {
    48             for (Yuint j = 0; j < stacks - 1; j++)         
    49             {
    50                 nOffset = (half + (i*(stacks - 1) + j)) * indexStriding;
    51                 lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
    52                 lineIndexPtr->index0 = j*slices + i;
    53                 lineIndexPtr->index1 = (j + 1)*slices + i;
    54             }
    55         }
    56     }
    57     else
    58     {
    59         YsLineIndex32* lineIndexPtr = NULL;
    60 
    61         //
    62         for (Yuint j = 0; j < stacks; j++)                 
    63         {
    64             for (Yuint i = 0; i < slices - 1; i++)         
    65             {
    66                 nOffset = ((j*(slices - 1) + i)) * indexStriding;
    67                 lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
    68                 lineIndexPtr->index0 = j*slices + i;
    69                 lineIndexPtr->index1 = j*slices + i + 1;
    70             }
    71         }
    72 
    73         //
    74         Yuint half = (slices - 1) * stacks;
    75         for (Yuint i = 0; i < slices; i++)                 
    76         {
    77             for (Yuint j = 0; j < stacks - 1; j++)         
    78             {
    79                 nOffset = (half + (i*(stacks - 1) + j)) * indexStriding;
    80                 lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
    81                 lineIndexPtr->index0 = j*slices + i;
    82                 lineIndexPtr->index1 = (j + 1)*slices + i;
    83             }
    84         }
    85     }
    86 
    87     return true;
    88 }
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  • 原文地址:https://www.cnblogs.com/WhyEngine/p/3415234.html
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