[7] 金字塔(Pyramid)图形的生成算法

最新推荐文章于 2023-09-14 16:30:58 发布

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最新推荐文章于 2023-09-14 16:30:58 发布

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本文介绍了一种生成金字塔三维模型的方法，包括顶点数据、三角形索引及线框索引的创建过程。根据不同的参数设置，可以调整金字塔的位置和尺寸。

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顶点数据的生成

 1 bool                        YfBuildPyramidVertices
 2 (
 3     Yreal                   width, 
 4     Yreal                   length, 
 5     Yreal                   height, 
 6     YeOriginPose            originPose, 
 7     Yuint                   vertexStriding, 
 8     Yuint                   vertexPos,
 9     void*                   pVerticesBuffer
10 )
11 {
12     if (!pVerticesBuffer)
13     {
14         return false;
15     }
16 
17     Yuint numVertices  = 5;
18 
19     char* vertexPtr   = (char*)pVerticesBuffer + vertexPos;
20     YsVector3* curVertexPtr   = NULL;
21     Yuint nOffset = 0;
22 
23     YsVector3 vOriginOffset(-width / 2, -height / 2, -length / 2);
24     if (originPose == YE_ORIGIN_POSE_TOP)
25     {
26         vOriginOffset.y = -height;
27     }
28     else if (originPose == YE_ORIGIN_POSE_BOTTOM)
29     {
30         vOriginOffset.y = 0.0f;
31     }
32 
33     // 底四个顶点
34     for (Yuint j = 0; j < 2; j++)
35     {
36         for (Yuint i = 0; i < 2; i++)
37         {
38             nOffset = (j*2 + i) * vertexStriding;
39             curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
40             curVertexPtr->x = width*i + vOriginOffset.x;
41             curVertexPtr->y = vOriginOffset.y;
42             curVertexPtr->z = length*j + vOriginOffset.z;
43         }
44     }
45 
46     // 顶尖顶点
47     nOffset = 4 * vertexStriding;
48     curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
49     curVertexPtr->x = 0.0f;
50     curVertexPtr->y = height + vOriginOffset.y;
51     curVertexPtr->z = 0.0f;
52  
53     return true;
54 }

三角形索引数据的生成

 1 bool                        YfBuildPyramidTriIndices
 2 (
 3     YeIndexType             indexType,
 4     Yuint                   indexStriding,  
 5     Yuint                   indexPos,
 6     void*                   pTriIndicesBuffer
 7 )
 8 {
 9     if (!pTriIndicesBuffer)
10     {
11         return false;
12     }
13 
14     char* indexPtr = (char*)pTriIndicesBuffer + indexPos;
15     if (indexType == YE_INDEX_16_BIT)
16     {
17         YsTriIndex16* triIndexPtr = NULL;
18 
19         // bottom
20         triIndexPtr = (YsTriIndex16*)(indexPtr + 0*indexStriding);
21         triIndexPtr->index0 = 0; triIndexPtr->index1 = 1; triIndexPtr->index2 = 3;
22         triIndexPtr = (YsTriIndex16*)(indexPtr + 1*indexStriding);
23         triIndexPtr->index0 = 0; triIndexPtr->index1 = 3; triIndexPtr->index2 = 2;
24 
25         // 4 face
26         triIndexPtr = (YsTriIndex16*)(indexPtr + 2*indexStriding);
27         triIndexPtr->index0 = 4; triIndexPtr->index1 = 1; triIndexPtr->index2 = 0;
28         triIndexPtr = (YsTriIndex16*)(indexPtr + 3*indexStriding);
29         triIndexPtr->index0 = 4; triIndexPtr->index1 = 3; triIndexPtr->index2 = 1;
30         triIndexPtr = (YsTriIndex16*)(indexPtr + 4*indexStriding);
31         triIndexPtr->index0 = 4; triIndexPtr->index1 = 2; triIndexPtr->index2 = 3;
32         triIndexPtr = (YsTriIndex16*)(indexPtr + 5*indexStriding);                                                
33         triIndexPtr->index0 = 4; triIndexPtr->index1 = 0; triIndexPtr->index2 = 2;
34     }
35     else
36     {
37         YsTriIndex32* triIndexPtr = NULL;
38 
39         // bottom
40         triIndexPtr = (YsTriIndex32*)(indexPtr + 0*indexStriding);
41         triIndexPtr->index0 = 0; triIndexPtr->index1 = 1; triIndexPtr->index2 = 3;
42         triIndexPtr = (YsTriIndex32*)(indexPtr + 1*indexStriding);
43         triIndexPtr->index0 = 0; triIndexPtr->index1 = 3; triIndexPtr->index2 = 2;
44 
45         // 4 face
46         triIndexPtr = (YsTriIndex32*)(indexPtr + 2*indexStriding);
47         triIndexPtr->index0 = 4; triIndexPtr->index1 = 1; triIndexPtr->index2 = 0;
48         triIndexPtr = (YsTriIndex32*)(indexPtr + 3*indexStriding);
49         triIndexPtr->index0 = 4; triIndexPtr->index1 = 3; triIndexPtr->index2 = 1;
50         triIndexPtr = (YsTriIndex32*)(indexPtr + 4*indexStriding);
51         triIndexPtr->index0 = 4; triIndexPtr->index1 = 2; triIndexPtr->index2 = 3;
52         triIndexPtr = (YsTriIndex32*)(indexPtr + 5*indexStriding);                                                
53         triIndexPtr->index0 = 4; triIndexPtr->index1 = 0; triIndexPtr->index2 = 2;
54     }
55 
56     return true;
57 }

线框索引数据的生成

 1 bool                        YfBuildPyramidWireIndices
 2 (
 3     YeIndexType             indexType,
 4     Yuint                   indexStriding, 
 5     Yuint                   indexPos,
 6     void*                   pWireIndicesBuffer
 7 )
 8 {
 9     if (!pWireIndicesBuffer)
10     {
11         return false;
12     }
13 
14     Yuint numVertices = 5;
15     Yuint numLines    = 8;
16     if (indexType == YE_INDEX_16_BIT && 
17         numVertices > YD_MAX_UNSIGNED_INT16)
18     {
19         return false;
20     }
21 
22     // 索引赋值
23     char* indexPtr = (char*)pWireIndicesBuffer + indexPos;
24     Yuint nOffset = 0;
25     if (indexType == YE_INDEX_16_BIT)
26     {
27         YsLineIndex16* lineIndexPtr = NULL;
28         
29         // bottom
30         lineIndexPtr = (YsLineIndex16*)(indexPtr + 0*indexStriding);
31         lineIndexPtr->index0 = 0; lineIndexPtr->index1 = 1; 
32         lineIndexPtr = (YsLineIndex16*)(indexPtr + 1*indexStriding);
33         lineIndexPtr->index0 = 1; lineIndexPtr->index1 = 3; 
34         lineIndexPtr = (YsLineIndex16*)(indexPtr + 2*indexStriding);
35         lineIndexPtr->index0 = 3; lineIndexPtr->index1 = 2; 
36         lineIndexPtr = (YsLineIndex16*)(indexPtr + 3*indexStriding);
37         lineIndexPtr->index0 = 2; lineIndexPtr->index1 = 0; 
38 
39         // 4 lines
40         lineIndexPtr = (YsLineIndex16*)(indexPtr + 4*indexStriding);
41         lineIndexPtr->index0 = 4; lineIndexPtr->index1 = 0; 
42         lineIndexPtr = (YsLineIndex16*)(indexPtr + 5*indexStriding);
43         lineIndexPtr->index0 = 4; lineIndexPtr->index1 = 1; 
44         lineIndexPtr = (YsLineIndex16*)(indexPtr + 6*indexStriding);
45         lineIndexPtr->index0 = 4; lineIndexPtr->index1 = 2; 
46         lineIndexPtr = (YsLineIndex16*)(indexPtr + 7*indexStriding);
47         lineIndexPtr->index0 = 4; lineIndexPtr->index1 = 3; 
48     }
49     else
50     {
51         YsLineIndex32* lineIndexPtr = NULL;
52 
53         // bottom
54         lineIndexPtr = (YsLineIndex32*)(indexPtr + 0*indexStriding);
55         lineIndexPtr->index0 = 0; lineIndexPtr->index1 = 1; 
56         lineIndexPtr = (YsLineIndex32*)(indexPtr + 1*indexStriding);
57         lineIndexPtr->index0 = 1; lineIndexPtr->index1 = 3; 
58         lineIndexPtr = (YsLineIndex32*)(indexPtr + 2*indexStriding);
59         lineIndexPtr->index0 = 3; lineIndexPtr->index1 = 2; 
60         lineIndexPtr = (YsLineIndex32*)(indexPtr + 3*indexStriding);
61         lineIndexPtr->index0 = 2; lineIndexPtr->index1 = 0; 
62 
63         // 4 lines
64         lineIndexPtr = (YsLineIndex32*)(indexPtr + 4*indexStriding);
65         lineIndexPtr->index0 = 4; lineIndexPtr->index1 = 0; 
66         lineIndexPtr = (YsLineIndex32*)(indexPtr + 5*indexStriding);
67         lineIndexPtr->index0 = 4; lineIndexPtr->index1 = 1; 
68         lineIndexPtr = (YsLineIndex32*)(indexPtr + 6*indexStriding);
69         lineIndexPtr->index0 = 4; lineIndexPtr->index1 = 2; 
70         lineIndexPtr = (YsLineIndex32*)(indexPtr + 7*indexStriding);
71         lineIndexPtr->index0 = 4; lineIndexPtr->index1 = 3; 
72     }
73 
74     return true;
75 }