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[14] 齿轮(Gear Wheel)图形的生成算法

顶点数据的生成

 1 bool                        YfBuildGearwheelVertices
 2 (
 3     Yreal                   radius, 
 4     Yreal                   assistRadius, 
 5     Yreal                   height, 
 6     Yuint                   slices,
 7     YeOriginPose            originPose,
 8     Yuint                   vertexStriding, 
 9     Yuint                   vertexPos,
10     void*                   pVerticesBuffer
11 )
12 {
13     if (slices < 2 || !pVerticesBuffer)
14     {
15         return false;
16     }
17 
18     Yuint numVertices  = slices*4 + 2;
19 
20     // 顶点赋值
21     char* vertexPtr = (char*)pVerticesBuffer + vertexPos;
22     YsVector3* curVertexPtr   = NULL;
23     Yuint nOffset = 0;
24 
25     Yreal originOffsetY = 0.0f;
26     if (originPose == YE_ORIGIN_POSE_TOP)
27     {
28         originOffsetY = -height;
29     }
30     else if (originPose == YE_ORIGIN_POSE_CENTER)
31     {
32         originOffsetY = -height * 0.5f;
33     }
34 
35     // 柱顶顶点赋值
36     {
37         nOffset = 0;   
38         curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
39         curVertexPtr->x = 0.0f;
40         curVertexPtr->y = height + originOffsetY;
41         curVertexPtr->z = 0.0f;
42     }
43 
44     // 柱底顶点赋值
45     {
46         nOffset = (numVertices - 1) * vertexStriding;   
47         curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
48         curVertexPtr->x = 0.0f;
49         curVertexPtr->y = originOffsetY;
50         curVertexPtr->z = 0.0f;
51     }
52 
53     Yreal angleXZ;
54     Yreal posX, posZ;        
55     Yreal fRadius;
56     for (Yuint i = 0; i < 2*slices; i++)
57     {
58         angleXZ = YD_REAL_TWAIN_PI * i / (slices*2);
59         posX = yf_sin(angleXZ);
60         posZ = yf_cos(angleXZ);
61         fRadius = (i%2 == 0) ? radius : assistRadius;
62 
63         // 上顶点
64         {
65             nOffset = (1 + i) * vertexStriding; 
66             curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
67             curVertexPtr->x = fRadius * posX;
68             curVertexPtr->y = height + originOffsetY;
69             curVertexPtr->z = fRadius * posZ;
70         }
71 
72         // 下顶点
73         {
74             nOffset = (1 + 2*slices + i) * vertexStriding; 
75             curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
76             curVertexPtr->x = fRadius * posX;
77             curVertexPtr->y = originOffsetY;
78             curVertexPtr->z = fRadius * posZ;
79         }
80     }
81 
82     return true;
83 }

三角形索引数据的生成

 1 bool                        YfBuildGearwheelTriIndices
 2 (
 3     Yuint                   slices,
 4     YeIndexType             indexType,
 5     Yuint                   indexStriding,  
 6     Yuint                   indexPos,
 7     void*                   pTriIndicesBuffer
 8 )
 9 {
10     if (slices < 2 || !pTriIndicesBuffer)
11     {
12         return false;
13     }
14 
15     Yuint numVertices  = slices*4 + 2;
16     if (indexType == YE_INDEX_16_BIT && 
17         numVertices > YD_MAX_UNSIGNED_INT16)
18     {
19         return false;
20     }
21     Yuint numTriangles = slices * 8;
22 
23     // 索引赋值
24     char* indexPtr = (char*)pTriIndicesBuffer + indexPos;
25     Yuint nOffset = 0;
26     if (indexType == YE_INDEX_16_BIT)
27     {
28         YsTriIndex16* triIndexPtr = NULL;
29         for (Yuint i = 0; i < 2 * slices; i++)
30         {
31             nOffset = (i * 4) * indexStriding;
32             triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
33             triIndexPtr->index0 = 0;
34             triIndexPtr->index1 = 1 + i;
35             triIndexPtr->index2 = 1 + (i + 1) % (2*slices);
36 
37             nOffset += indexStriding;
38             triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
39             triIndexPtr->index0 = numVertices - 1;
40             triIndexPtr->index1 = 1 + slices*2 + (i + 1) % (2*slices);
41             triIndexPtr->index2 = 1 + slices*2 + i;
42 
43             nOffset += indexStriding;
44             triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
45             triIndexPtr->index0 = 1 + i;
46             triIndexPtr->index1 = 1 + slices*2 + i;
47             triIndexPtr->index2 = 1 + (i + 1) % (2*slices);
48 
49             nOffset += indexStriding;
50             triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
51             triIndexPtr->index0 = 1 + (i + 1) % (2*slices);
52             triIndexPtr->index1 = 1 + slices*2 + i;
53             triIndexPtr->index2 = 1 + slices*2 + (i + 1) % (2*slices);
54         }
55     }
56     else
57     {
58         YsTriIndex32* triIndexPtr = NULL;
59         for (Yuint i = 0; i < 2 * slices; i++)
60         {
61             nOffset = (i * 4) * indexStriding;
62             triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
63             triIndexPtr->index0 = 0;
64             triIndexPtr->index1 = 1 + i;
65             triIndexPtr->index2 = 1 + (i + 1) % (2*slices);
66 
67             nOffset += indexStriding;
68             triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
69             triIndexPtr->index0 = numVertices - 1;
70             triIndexPtr->index1 = 1 + slices*2 + (i + 1) % (2*slices);
71             triIndexPtr->index2 = 1 + slices*2 + i;
72 
73             nOffset += indexStriding;
74             triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
75             triIndexPtr->index0 = 1 + i;
76             triIndexPtr->index1 = 1 + slices*2 + i;
77             triIndexPtr->index2 = 1 + (i + 1) % (2*slices);
78 
79             nOffset += indexStriding;
80             triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
81             triIndexPtr->index0 = 1 + (i + 1) % (2*slices);
82             triIndexPtr->index1 = 1 + slices*2 + i;
83             triIndexPtr->index2 = 1 + slices*2 + (i + 1) % (2*slices);
84         }
85     }
86 
87     return true;
88 }

线框索引数据的生成

 1 bool                        YfBuildGearwheelWireIndices
 2 (
 3     Yuint                   slices,
 4     YeIndexType             indexType,
 5     Yuint                   indexStriding, 
 6     Yuint                   indexPos,
 7     void*                   pWireIndicesBuffer
 8 )
 9 {
10     if (slices < 2 || !pWireIndicesBuffer)
11     {
12         return false;
13     }
14 
15     Yuint numVertices = (slices*2) * 2 + 2;
16     Yuint numLines    = (slices*2) * 5;
17     if (indexType == YE_INDEX_16_BIT && 
18         numVertices > YD_MAX_UNSIGNED_INT16)
19     {
20         return false;
21     }
22 
23     // 索引赋值
24     char* indexPtr = (char*)pWireIndicesBuffer + indexPos;
25     Yuint nOffset = 0;
26     if (indexType == YE_INDEX_16_BIT)
27     {
28         YsLineIndex16* lineIndexPtr = NULL;
29         for (Yuint i = 0; i < 2 * slices; i++)
30         {
31             nOffset = (i * 3) * indexStriding;
32             lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
33             lineIndexPtr->index0 = 1 + i;
34             lineIndexPtr->index1 = 1 + (i + 1)%(slices*2);
35 
36             nOffset += indexStriding;
37             lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
38             lineIndexPtr->index0 = 1 + slices*2 + i;
39             lineIndexPtr->index1 = 1 + slices*2 + (i + 1)%(slices*2);
40 
41             nOffset += indexStriding;
42             lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
43             lineIndexPtr->index0 = 1 + i;
44             lineIndexPtr->index1 = 1 + slices*2 + i;
45         }
46         
47         Yuint half = 6 * slices * indexStriding;
48         for (Yuint i = 0; i < slices; i++)
49         {
50             nOffset = half + (i * 2) * indexStriding;
51             lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
52             lineIndexPtr->index0 = 0;
53             lineIndexPtr->index1 = 1 + i*2 + 1;
54 
55             nOffset += indexStriding;
56             lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
57             lineIndexPtr->index0 = numVertices - 1;
58             lineIndexPtr->index1 = 1 + slices*2 + i*2 + 1;
59         }
60     }
61     else
62     {
63         YsLineIndex32* lineIndexPtr = NULL;
64         for (Yuint i = 0; i < 2 * slices; i++)
65         {
66             nOffset = (i * 3) * indexStriding;
67             lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
68             lineIndexPtr->index0 = 1 + i;
69             lineIndexPtr->index1 = 1 + (i + 1)%(slices*2);
70 
71             nOffset += indexStriding;
72             lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
73             lineIndexPtr->index0 = 1 + slices*2 + i;
74             lineIndexPtr->index1 = 1 + slices*2 + (i + 1)%(slices*2);
75 
76             nOffset += indexStriding;
77             lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
78             lineIndexPtr->index0 = 1 + i;
79             lineIndexPtr->index1 = 1 + slices*2 + i;
80         }
81 
82         Yuint half = 6 * slices * indexStriding;
83         for (Yuint i = 0; i < slices; i++)
84         {
85             nOffset = half + (i * 2) * indexStriding;
86             lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
87             lineIndexPtr->index0 = 0;
88             lineIndexPtr->index1 = 1 + i*2 + 1;
89 
90             nOffset += indexStriding;
91             lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
92             lineIndexPtr->index0 = numVertices - 1;
93             lineIndexPtr->index1 = 1 + slices*2 + i*2 + 1;
94         }
95     }
96 
97     return true;
98 }

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原文地址：https://www.cnblogs.com/WhyEngine/p/3415256.html