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[0] 各类图形的数据大小获得

要创建一个几何图形,先得知道其数据大小,以申请合适的内存.
  1 bool                        YfCalculateGeometryBufferSize
  2 (
  3     YeGraphType             graphType,      
  4     Yuint                   slices, 
  5     Yuint                   stacks,           
  6     OUT Yuint&              numVertices,        // 顶点数目
  7     OUT Yuint&              numTriangles,       // 三角形数目
  8     OUT Yuint&              numLines            // 线段数目
  9 )
 10 {
 11     switch (graphType)
 12     {
 13     case YE_GRAPH_PLANE:
 14         {
 15             if (slices < 2 || stacks < 2)
 16             {
 17                 return false;
 18             }
 19             numVertices  = slices * stacks;
 20             numTriangles = (slices - 1) * (stacks - 1) * 2;
 21             numLines     = slices * (stacks - 1) +(slices - 1) * stacks;
 22         }
 23         break;
 24 
 25     case YE_GRAPH_BOX:
 26         {
 27             numVertices  = 8;
 28             numTriangles = 12;
 29             numLines     = 12;
 30         }
 31         break;
 32 
 33     case YE_GRAPH_SPHERE:
 34         {
 35             if (slices < 2 || stacks < 3)
 36             {
 37                 return false;
 38             }
 39             numVertices  = slices * (stacks - 2) + 2;
 40             numTriangles = slices * (stacks - 2) * 2;
 41             numLines     = slices * (stacks - 2) + slices * (stacks - 1);
 42         }
 43         break;
 44 
 45     case YE_GRAPH_DRUM:
 46         {
 47             if (slices < 2 || stacks < 3)
 48             {
 49                 return false;
 50             }
 51             numVertices  = slices * stacks + 2;
 52             numTriangles = slices * stacks * 2;
 53             numLines     = slices * stacks + slices * (stacks + 1);
 54         }
 55         break;
 56 
 57     case YE_GRAPH_HEMISPHERE:
 58         {
 59             if (slices < 2 || stacks < 3)
 60             {
 61                 return false;
 62             }
 63             numVertices  = slices * (stacks - 1) + 1;
 64             numTriangles = slices * (stacks - 2) * 2 + slices;
 65             numLines     = slices * (stacks - 1) * 2;
 66         }
 67         break;
 68 
 69     case YE_GRAPH_CONE:
 70         {
 71             if (slices < 2)
 72             {
 73                 return false;
 74             }
 75             numVertices  = slices + 2;
 76             numTriangles = slices * 2;
 77             numLines     = slices * 2;
 78         }
 79         break;
 80 
 81     case YE_GRAPH_CYLINDER:
 82         { 
 83             if (slices < 2)
 84             {
 85                 return false;
 86             }
 87             numVertices  = slices * 2 + 2;
 88             numTriangles = slices * 4;
 89             numLines     = slices * 5;
 90         }
 91         break;
 92 
 93     case YE_GRAPH_CAPSULE:
 94         {
 95             Yuint halfStacks = stacks / 2;
 96             if (slices < 2 || halfStacks < 2)
 97             {
 98                 return false;
 99             }
100             numVertices  = slices * (halfStacks - 1) * 2 + 2;
101             numTriangles = slices * (halfStacks - 1) * 4;
102             numLines     = slices * (halfStacks - 1) * 2 + slices * (2 * halfStacks - 1);
103         }
104         break;
105 
106     case YE_GRAPH_PYRAMID:
107         {
108             numVertices  = 5;
109             numTriangles = 6;
110             numLines     = 8;
111         }
112         break;
113 
114     case YE_GRAPH_ROUND:
115         {
116             if (slices < 3)
117             {
118                 return false;
119             }
120             numVertices  = slices + 1;
121             numTriangles = slices;
122             numLines     = slices;
123         }
124         break;
125 
126     case YE_GRAPH_RING:
127         {
128             if (slices < 2 || stacks < 3)
129             {
130                 return false;
131             }
132             numVertices  = slices * stacks;
133             numTriangles = slices * stacks * 2;
134             numLines     = slices * stacks * 2;
135         }
136         break;
137 
138     case YE_GRAPH_PIPE:
139         {
140             if (slices < 2)
141             {
142                 return false;
143             }
144             numVertices  = slices * 4;
145             numTriangles = slices * 8;
146             numLines     = slices * 8;
147         }
148         break;
149 
150     case YE_GRAPH_WEDGE:
151         {
152             numVertices  = 6;
153             numTriangles = 8;
154             numLines     = 9;
155         }
156         break;
157 
158     case YE_GRAPH_FAN:
159         {
160             if (slices < 2)
161             {
162                 return false;
163             }
164             numVertices  = (slices + 1) * 2;
165             numTriangles = slices * 4;
166             numLines     = slices + (slices-1) * 2 + 5;
167         }
168         break;
169 
170     case YE_GRAPH_ARC:
171         {
172             if (slices < 2 || stacks < 3)
173             {
174                 return false;
175             }
176             numVertices  = slices * (stacks - 1) + 1;
177             numTriangles = slices * (stacks - 2) * 2 + slices;
178             numLines     = slices * (stacks - 1) * 2;
179         }
180         break;
181 
182     case YE_GRAPH_GEARWHEEL:
183         {
184             if (slices < 3)
185             {
186                 return false;
187             }
188             numVertices  = (slices*2) * 2 + 2;
189             numTriangles = slices * 8;
190             numLines     = (slices*2) * 5;
191         }
192         break;
193 
194     case YE_GRAPH_STAR:
195         {
196             if (slices < 3)
197             {
198                 return false;
199             }
200             numVertices  = (slices*2) + 2;
201             numTriangles = slices * 4;
202             numLines     = slices * 5;
203         }
204         break;
205 
206     case YE_GRAPH_SPIRE:
207         {
208             if (stacks < 1 || slices < 3)
209             {
210                 return false;
211             }
212             numVertices  = 2 + stacks * 2;
213             numTriangles = stacks * 2;
214             numLines     = 1 + stacks * 3;
215         }
216         break;
217 
218     case YE_GRAPH_STAIRS:
219         {
220             if (stacks < 1)
221             {
222                 return false;
223             }
224             numVertices  = 2 + stacks * 4;
225             numTriangles = stacks * 8;
226             numLines     = 1 + stacks * 8;
227         }
228         break;
229 
230     case YE_GRAPH_SPIRAL_STAIRS:
231         {
232             if (stacks < 1)
233             {
234                 return false;
235             }
236             numVertices  = 2 + stacks * 4;
237             numTriangles = stacks * 8;
238             numLines     = 1 + stacks * 8;
239         }
240         break;
241 
242     default:
243         {
244             numVertices  = 0;
245             numTriangles = 0;
246             numLines     = 0;
247             return false;
248         }
249         break;
250     }
251 
252     return true;
253 }
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原文地址：https://www.cnblogs.com/WhyEngine/p/3415233.html