Ogre源代码浅析——Mesh⽂件结构及加载（⼀） Ogre的模型数据（模型顶点数，每个顶点的3D坐标值等等）保存在.mesh⽂件中，mesh⽂件的结构如下（版本号：MeshSerializer_v1.8）:
1enum MeshChunkID {
2 M_HEADER = 0x1000,
3// char* version : Version number check香玲核桃
4 M_MESH = 0x3000,
5// bool skeletallyAnimated // important flag which affects h/w buffer policies
6// Optional M_GEOMETRY chunk
7 M_SUBMESH = 0x4000,
8// char* materialName
9// bool uSharedVertices
10// unsigned int indexCount
11// bool indexes32Bit
断定的意思是什么12// unsigned int* faceVertexIndices (indexCount)
13// OR
14// unsigned short* faceVertexIndices (indexCount)
15// M_GEOMETRY chunk (Optional: prent only if uSharedVertices = fal)
16 M_SUBMESH_OPERATION = 0x4010, // optional, trilist assumed if missing
17// unsigned short operationType
18 M_SUBMESH_BONE_ASSIGNMENT = 0x4100,
新斗记19// Optional bone weights (repeating ction)
20// unsigned int vertexIndex;
21// unsigned short boneIndex;
22// float weight;
23// Optional chunk that matches a texture name to an alias
24// a texture alias is nt to the submesh material to u this texture name
25// instead of the one in the texture unit with a matching alias name
26 M_SUBMESH_TEXTURE_ALIAS = 0x4200, // Repeating ction
27// char* aliasName;
28// char* textureName;
29
30 M_GEOMETRY = 0x5000, // NB this chunk is embedded within M_MESH and M_SUBMESH
31// unsigned int vertexCount
32 M_GEOMETRY_VERTEX_DECLARATION = 0x5100,
33 M_GEOMETRY_VERTEX_ELEMENT = 0x5110, // Repeating ction
34// unsigned short source; // buffer bind source
35// unsigned short type; // VertexElementType
36// unsigned short mantic; // VertexElementSemantic
37// unsigned short offt; // start offt in buffer in bytes
38// unsigned short index; // index of the mantic (for colours and texture coords)
39 M_GEOMETRY_VERTEX_BUFFER = 0x5200, // Repeating ction
40// unsigned short bindIndex; // Index to bind this buffer to
41// unsigned short vertexSize; // Per-vertex size, must agree with declaration at this index
42 M_GEOMETRY_VERTEX_BUFFER_DATA = 0x5210,
43// raw buffer data
44 M_MESH_SKELETON_LINK = 0x6000,
45// Optional link to skeleton
46// char* skeletonName : name of .skeleton to u
47 M_MESH_BONE_ASSIGNMENT = 0x7000,
48// Optional bone weights (repeating ction)
49// unsigned int vertexIndex;
50// unsigned short boneIndex;
51// float weight;
52 M_MESH_LOD = 0x8000,
53// Optional LOD information
54// string strategyName;
55// unsigned short numLevels;
56// bool manual; (true for manual alternate meshes, fal for generated)
57 M_MESH_LOD_USAGE = 0x8100,
58// Repeating ction, ordered in increasing depth
59// NB LOD 0 (full detail from 0 depth) is omitted
60// LOD value - this is a distance, a pixel count etc, bad on strategy
61// float lodValue;
62 M_MESH_LOD_MANUAL = 0x8110,
63// Required if M_MESH_LOD ction manual = true
64// String manualMeshName;
65 M_MESH_LOD_GENERATED = 0x8120,
66// Required if M_MESH_LOD ction manual = fal
67// Repeating ction (1 per submesh)孕妇产后吃什么好
68// unsigned int indexCount;
69// bool indexes32Bit
70// unsigned short* faceIndexes; (indexCount)
71// OR
72// unsigned int* faceIndexes; (indexCount)
73 M_MESH_BOUNDS = 0x9000,
74// float minx, miny, minz
75// float maxx, maxy, maxz
76// float radius
77
78// Added By DrEvil
79// optional chunk that contains a table of submesh indexes and the names of
80// the sub-meshes.
81 M_SUBMESH_NAME_TABLE = 0xA000,
82// Subchunks of the name table. Each chunk contains an index & string
83 M_SUBMESH_NAME_TABLE_ELEMENT = 0xA100,
84// short index
85// char* name
86
87// Optional chunk which stores precomputed edge data
88 M_EDGE_LISTS = 0xB000,
89// Each LOD has a parate edge list
90 M_EDGE_LIST_LOD = 0xB100,
91// unsigned short lodIndex
92// bool isManual // If manual, no edge data here, loaded from manual mesh 93// bool isClod
94// unsigned long numTriangles
95// unsigned long numEdgeGroups
96// Triangle* triangleList
97// unsigned long indexSet
98// unsigned long vertexSet
99// unsigned long vertIndex[3]
100// unsigned long sharedVertIndex[3]
101// float normal[4]
102
103 M_EDGE_GROUP = 0xB110,
104// unsigned long vertexSet
105// unsigned long triStart
106// unsigned long triCount
107// unsigned long numEdges
108// Edge* edgeList
109// unsigned long triIndex[2]
110// unsigned long vertIndex[2]
111// unsigned long sharedVertIndex[2]
112// bool degenerate
113
114// Optional pos ction, referred to by po keyframes
115 M_POSES = 0xC000,
116 M_POSE = 0xC100,
117// char* name (may be blank)
三亚梦幻水上乐园
118// unsigned short target // 0 for shared geometry,
119// 1+ for submesh index + 1
120// bool includesNormals [1.8+]
121 M_POSE_VERTEX = 0xC111,
122// unsigned long vertexIndex
123// float xofft, yofft, zofft
124// float xnormal, ynormal, znormal (optional, 1.8+)
125// Optional vertex animation chunk
126 M_ANIMATIONS = 0xD000,
127 M_ANIMATION = 0xD100,
128// char* name
129// float length
130 M_ANIMATION_BASEINFO = 0xD105,
131// [Optional] ba keyframe information (po animation only)
132// char* baAnimationName (blank for lf)
133// float baKeyFrameTime
134
135 M_ANIMATION_TRACK = 0xD110,
136// unsigned short type // 1 == morph, 2 == po
137// unsigned short target // 0 for shared geometry,
138// 1+ for submesh index + 1
139 M_ANIMATION_MORPH_KEYFRAME = 0xD111,
140// float time
141// bool includesNormals [1.8+]
142// float x,y,z // repeat by number of vertices in original geometry
143 M_ANIMATION_POSE_KEYFRAME = 0xD112,
144// float time
145 M_ANIMATION_POSE_REF = 0xD113, // repeat for number of referenced pos 146// unsigned short poIndex
147// float influence
148
塞上曲149// Optional submesh extreme vertex list chink
150 M_TABLE_EXTREMES = 0xE000,
151// unsigned short submesh_index;
152// float extremes [n_extremes][3];
153
154/* Version 1.2 of the .mesh format (deprecated)
155 enum MeshChunkID {
156 M_HEADER = 0x1000,
157 // char* version : Version number check
158 M_MESH = 0x3000,
159 // bool skeletallyAnimated // important flag which affects h/w buffer policies土增清算条件
160 // Optional M_GEOMETRY chunk
161 M_SUBMESH = 0x4000,
162 // char* materialName
163 // bool uSharedVertices
164 // unsigned int indexCount
165 // bool indexes32Bit
166 // unsigned int* faceVertexIndices (indexCount)
167 // OR
168 // unsigned short* faceVertexIndices (indexCount)
169 // M_GEOMETRY chunk (Optional: prent only if uSharedVertices = fal)
170 M_SUBMESH_OPERATION = 0x4010, // optional, trilist assumed if missing
171 // unsigned short operationType
172 M_SUBMESH_BONE_ASSIGNMENT = 0x4100,
173 // Optional bone weights (repeating ction)
174 // unsigned int vertexIndex;
175 // unsigned short boneIndex;
176 // float weight;
177 M_GEOMETRY = 0x5000, // NB this chunk is embedded within M_MESH and M_SUBMESH
闺蜜英语
178*/
179// unsigned int vertexCount
180// float* pVertices (x, y, z order x numVertices)
181 M_GEOMETRY_NORMALS = 0x5100, //(Optional)
182// float* pNormals (x, y, z order x numVertices)
183 M_GEOMETRY_COLOURS = 0x5200, //(Optional)
184// unsigned long* pColours (RGBA 8888 format x numVertices)
185 M_GEOMETRY_TEXCOORDS = 0x5300//(Optional, REPEATABLE, each one adds an extra t)
186// unsigned short dimensions (1 for 1D, 2 for 2D, 3 for 3D)
187// float* pTexCoords (u [v] [w] order, dimensions x numVertices)
188/*
189 M_MESH_SKELETON_LINK = 0x6000,
190 // Optional link to skeleton
191 // char* skeletonName : name of .skeleton to u
192 M_MESH_BONE_ASSIGNMENT = 0x7000,
193 // Optional bone weights (repeating ction)
194 // unsigned int vertexIndex;
195 // unsigned short boneIndex;
196 // float weight;
197 M_MESH_LOD = 0x8000,
198 // Optional LOD information
199 // unsigned short numLevels;
200 // bool manual; (true for manual alternate meshes, fal for generated)
201 M_MESH_LOD_USAGE = 0x8100,
202 // Repeating ction, ordered in increasing depth
203 // NB LOD 0 (full detail from 0 depth) is omitted
204 // float fromSquaredDepth;
205 M_MESH_LOD_MANUAL = 0x8110,
206 // Required if M_MESH_LOD ction manual = true
207 // String manualMeshName;
208 M_MESH_LOD_GENERATED = 0x8120,
209 // Required if M_MESH_LOD ction manual = fal
210 // Repeating ction (1 per submesh)
211 // unsigned int indexCount;
212 // bool indexes32Bit
213 // unsigned short* faceIndexes; (indexCount)
214 // OR
215 // unsigned int* faceIndexes; (indexCount)
216 M_MESH_BOUNDS = 0x9000
217 // float minx, miny, minz
218 // float maxx, maxy, maxz
219 // float radius
220
221 // Added By DrEvil
222 // optional chunk that contains a table of submesh indexes and the names of
223 // the sub-meshes.
224 M_SUBMESH_NAME_TABLE,
225 // Subchunks of the name table. Each chunk contains an index & string
226 M_SUBMESH_NAME_TABLE_ELEMENT,
227 // short index
228 // char* name
229
230*/
231 };
与⼀般的3D⽂件格式类似，Ogre的mesh⽂件数据结构为树。构成mesh⽂件的基本数据单位是chunk，每个chunk由三部分组成：
1 unsigned short CHUNK_ID : one of the following chunk ids identifying the chunk
2 unsigned long LENGTH : length of the chunk in bytes, including this header
3void* DATA : the data, which may contain other sub-chunks (various data types)
CHUNK_ID⽤来标⽰各个chunk，⽽各chunk的实际数据则保存在相应的DATA域中。各chunk在id和数据域之外还有⼀个长度域（长度域也可以看作是数据域中的⼀项），⽤来描述本chunk的数据字节数。如果⾃定义的mesh⽂件结构⽐较复杂，嵌套层⽐较深，有了长度域就可以在⽂件读取过程中，帮助程序快速定位到指定的数据段；chunk的长度域还有⼀个作⽤，就是可以在⽂件读取过程中进⾏数据校验。
另外，随着Ogre引擎的不断改进，mesh⽂件衍⽣出多个版本，不同版本的⽂件结构是有所变化的，这⼀点从上⾯第⼀段代码（154-178⾏与2-30⾏的对⽐）中可以反应出来。mesh⽂件数据⽤⼆进制格式保存，所有版本的mesh⽂件开头两个字节都以0x1000作为⽂件标识，接
下来的21-22个字节是⼀个字符串，⽤来表⽰mesh⽂件的版本号。在对⽂件数据进⾏读取时，Ogre会根据版本号的不同选择相应的⽂件串⾏器（MeshSerializer），对mesh⽂件数据进⾏读取。
