glmodel.cpp

#include <cmath>
using namespace std;

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <glmodel.h>
#include <gleasymath.h>
#include<QImage>
#include<QFileInfo>

#ifndef GL_PI
#define GL_PI 3.14159265358979323846
#endif

/* defines */
#define T(x) model->triangles[(x)]
/* 枚举值代表坐标 */
enum { X, Y, Z, W };  //节点元素


//通用节点
typedef struct _GLMnode {
	int           index;
	bool        averaged;
	struct _GLMnode* next;
} GLMnode;

/* 为字符串分配内存 */
static char* stralloc(const char *string)
{
	char *copy;

	copy = (char*)malloc(strlen(string) + 1);
	if (copy == NULL)
		return NULL;
	strcpy(copy, string);
	return copy;
}

/* _glmWeldVectors: eliminate (weld) vectors that are within an
* epsilon of each other.//在阈值内消除或者合并？？？？
*
* vectors    - array of GLfloat[3]'s to be welded
* numvectors - number of GLfloat[3]'s in vectors
* epsilon    - maximum difference between vectors
*
*/
GLfloat* _glmWeldVectors(GLfloat* vectors, GLuint* numvectors, GLfloat epsilon)
{
	GLfloat* copies;
	GLuint   copied;
	GLuint   i, j;

	copies = (GLfloat*)malloc(sizeof(GLfloat) * 3 * (*numvectors + 1));
	memcpy(copies, vectors, (sizeof(GLfloat) * 3 * (*numvectors + 1)));

	copied = 1;
	for (i = 1; i <= *numvectors; i++) {
		for (j = 1; j <= copied; j++) {
			if (_glmEqual(&vectors[3 * i], &copies[3 * j], epsilon)) {
				goto duplicate;
			}
		}

		/* must not be any duplicates -- add to the copies array */
		copies[3 * copied + 0] = vectors[3 * i + 0];
		copies[3 * copied + 1] = vectors[3 * i + 1];
		copies[3 * copied + 2] = vectors[3 * i + 2];
		j = copied;        /* pass this along for below */
		copied++;

	duplicate:
		/* set the first component of this vector to point at the correct
		index into the new copies array */
		vectors[3 * i + 0] = (GLfloat)j;
	}

	*numvectors = copied - 1;
	return copies;
}

/* glmWeld: eliminate (weld) vectors that are within an epsilon of
* each other.
*
* model      - initialized GLMmodel structure
* epsilon    - maximum difference between vertices
*              ( 0.00001 is a good start for a unitized model)
*
*/
GLvoid glmWeld(GLMmodel* model, GLfloat epsilon)
{
	GLfloat* vectors;
	GLfloat* copies;
	GLuint   numvectors;
	GLuint   i;

	/* vertices */
	numvectors = model->numvertices;
	vectors = model->vertices;
	copies = _glmWeldVectors(vectors, &numvectors, epsilon);

	printf("glmWeld(): %d redundant vertices.\n",
		model->numvertices - numvectors - 1);

	for (i = 0; i < model->numtriangles; i++) {
		T(i).vindices[0] = (int)vectors[3 * T(i).vindices[0] + 0];
		T(i).vindices[1] = (int)vectors[3 * T(i).vindices[1] + 0];
		T(i).vindices[2] = (int)vectors[3 * T(i).vindices[2] + 0];
	}

	/* free space for old vertices */
	free(vectors);

	/* allocate space for the new vertices */
	model->numvertices = numvectors;
	model->vertices = (GLfloat*)malloc(sizeof(GLfloat) *
		3 * (model->numvertices + 1));

	/* copy the optimized vertices into the actual vertex list */
	for (i = 1; i <= model->numvertices; i++) {
		model->vertices[3 * i + 0] = copies[3 * i + 0];
		model->vertices[3 * i + 1] = copies[3 * i + 1];
		model->vertices[3 * i + 2] = copies[3 * i + 2];
	}

	free(copies);
}

//找到模型中的组
GLMgroup* _glmFindGroup(GLMmodel* model, char* name)
{
	GLMgroup* group;

	assert(model);

	group = model->groups;
	while (group) {
		if (!strcmp(name, group->name))//strcmp相等返回0，不等返回1
			break;
		group = group->next;
	}

	return group;
}

//模型中添加一个组，如果为null则新建一个组
GLMgroup* _glmAddGroup(GLMmodel* model, char* name)
{
	GLMgroup* group;

	group = _glmFindGroup(model, name);
	if (!group) {
		group = (GLMgroup*)malloc(sizeof(GLMgroup));

		group->name = stralloc(name);
		group->material = 0;
		group->numtriangles = 0;
		group->triangles = NULL;
		group->next = model->groups;//将模型的当前组索引赋给该组下一个组（实际是上一个）
		model->groups = group;//该组赋给模型的当前组索引

		model->numgroups++;
	}

	return group;
}

//在模型中找到材质
int _glmFindMaterial(GLMmodel* model, char* name)
{
	GLuint i;

	for (i = 0; i < model->nummaterials; i++) {
		if (!strcmp(model->materials[i].name, name))
			goto found;
	}
	/* didn't find the name, so set it as the default material */
	printf("_glmFindMaterial():  can't find material \"%s\".\n", name);
	i = 0;

found:
	return i;
}

//返回指定路径的文件夹
static char* _glmDirName(char* path)
{
	char* dir;
	char* s;

	dir = stralloc(path);

	s = strrchr(dir, '/');//查找字符在指定字符串中从左面开始的最后一次出现的位置，如果成功，返回该字符以及其后面的字符
	if (s)
		s[1] = '\0';
	else
		dir[0] = '\0';

	return dir;
}

/* //ppm格式纹理文件
	返回值：是否正确读取ppm

	map_Kd Image\001.png
	*/
int _glmReadPPM(GLuint textureArray[], char* filename, int textureID)
{
	int h, w, i;
	//int no_read;
	char buf[200], temp[80];
	FILE *fp;
	static int _teximageWidth, _teximageHeight;
	GLubyte *_teximage;

	if ((fp = fopen(filename, "r")) == NULL) {
		printf("File cannot open!!\n");
		return 0;
	}
	else {
		fscanf(fp, "%s\n", buf);  /* GET "P6" */
		fscanf(fp, "%s", temp);
		while (temp[0] == '#') {
			while (fgetc(fp) != '\n');
			fscanf(fp, "%s", temp);
		}
		w = atoi(temp);//是把字符串转换成整型数的一个函数
		fscanf(fp, " %d\n", &h);
		fscanf(fp, "%s\n", temp);

		_teximage = (GLubyte*)malloc(sizeof(GLubyte)*w*h * 3);

		for (i = 0; i < w*h * 3; i++) {
			_teximage[i] = (GLubyte)fgetc(fp);
		}
		_teximageWidth = w;
		_teximageHeight = h;
		fclose(fp);

		/*
		* Generate a texture with the associative texture ID stored in
		* the array, sets the alignment requirements for the start of each pixel
		* row in memory. Bind the texture to the texture arrays index and
		* init the texture
		*/

		glGenTextures(1, &textureArray[textureID]);
		glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
		glBindTexture(GL_TEXTURE_2D, textureArray[textureID]);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
		glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
		gluBuild2DMipmaps(GL_TEXTURE_2D, 3, w, h, GL_RGB,
			GL_UNSIGNED_BYTE, (GLvoid*)_teximage);

		printf("texture %d : %s is loaded\n", textureArray[textureID], filename);
		/*
		glTexImage2D(GL_TEXTURE_2D, 0, 3, w, h, 0, GL_RGB,
		GL_UNSIGNED_BYTE, (GLvoid*)_teximage);
		*/
		free(_teximage);
	}
	return 1;
}
// 装化为最接近的2的阶乘数
int RoundUpToTheNextHighestPowerOf2(unsigned int v)
{
	v--;
	v |= v >> 1;
	v |= v >> 2;
	v |= v >> 4;
	v |= v >> 8;
	v |= v >> 16;
	v++;
	return v;
}
//重写读取格式文件的函数，将读取到的有效路径保存到一个集合中去
void _glmReadPNG(GLMmodel* model, GLuint textureArray[], char* filename, int textureID)
{
	FILE *fp;
	if ((fp = fopen(filename, "r")) == NULL) {
		printf("File cannot open!!\n");
	}
	else
	{
		glEnable(GL_TEXTURE_2D);
		GLint MaxTextureSize;
		glGetIntegerv(GL_MAX_TEXTURE_SIZE, &MaxTextureSize);

		QImage img, imgScaled, imgGL;
		QFileInfo fi(QString::fromLocal8Bit(filename));
		QString filaPath = fi.absoluteFilePath();
		bool res = img.load(fi.absoluteFilePath());
		if (res)
		{
			int bestW = RoundUpToTheNextHighestPowerOf2(img.width());
			int bestH = RoundUpToTheNextHighestPowerOf2(img.height());
			while (bestW > MaxTextureSize) bestW /= 2;
			while (bestH > MaxTextureSize) bestH /= 2;

			imgScaled = img.scaled(bestW, bestH, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
			//imgGL = convertToGLFormat(imgScaled);
			imgGL = imgScaled;

			glGenTextures(1, (GLuint*)&(textureArray[textureID]));
			glBindTexture(GL_TEXTURE_2D, (GLuint)textureArray[textureID]);
			//glTexImage2D(GL_TEXTURE_2D, 0, 3, imgGL.width(), imgGL.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, imgGL.bits());

			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
			glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
			gluBuild2DMipmaps(GL_TEXTURE_2D, 3, imgGL.width(), imgGL.height(), GL_RGBA, GL_UNSIGNED_BYTE, imgGL.bits());
		}

		glDisable(GL_TEXTURE_2D);
		fclose(fp);
	}
}

//读取mtl贴图格式文件
static void _glmReadMTL(GLMmodel* model, char* name)
{
	FILE* file;
	char* dir;
	char* filename;
	char* picturefilename;

	char  buf[128];
	GLuint nummaterials, i;

	dir = _glmDirName(model->pathname);
	filename = (char*)malloc(sizeof(char) * (strlen(dir) + strlen(name) + 1));
	strcpy(filename, dir);//复制
	strcat(filename, name);//连接字符串获得贴图文件路径

	//free(dir);//释放分配的内存空间

	/* 只读方式打开文件 */
	file = fopen(filename, "r");//r+是读写方式打开
	if (!file) {
		fprintf(stderr, "_glmReadMTL() failed: can't open material file \"%s\".\n",
			filename);
		exit(1);
	}
	free(filename);//释放文件名路径资源

	/* 计算材质的个数 */
	nummaterials = 1;//从1开始方便后面分配内存
	while (fscanf(file, "%s", buf) != EOF) {
		switch (buf[0]) {
		case '#':
			fgets(buf, sizeof(buf), file);
			break;
		case 'n':        /* newmtl */
			fgets(buf, sizeof(buf), file);
			nummaterials++;
			sscanf(buf, "%s %s", buf, buf);
			break;
		default:
			fgets(buf, sizeof(buf), file);
			break;
		}
	}
	rewind(file);//重置指针到文件流的头部

	/* 为材质对象分配内存 */
	model->materials = (GLMmaterial*)malloc(sizeof(GLMmaterial) * nummaterials);
	model->nummaterials = nummaterials;

	/* 设置默认材质 */
	for (i = 0; i < nummaterials; i++) {
		model->materials[i].name = NULL;
		model->materials[i].shininess = 0;
		model->materials[i].diffuse[0] = 0.8;
		model->materials[i].diffuse[1] = 0.8;
		model->materials[i].diffuse[2] = 0.8;
		model->materials[i].diffuse[3] = 1.0;
		model->materials[i].ambient[0] = 0.2;
		model->materials[i].ambient[1] = 0.2;
		model->materials[i].ambient[2] = 0.2;
		model->materials[i].ambient[3] = 1.0;
		model->materials[i].specular[0] = 0.0;
		model->materials[i].specular[1] = 0.0;
		model->materials[i].specular[2] = 0.0;
		model->materials[i].specular[3] = 1.0;
		model->materials[i].map_file = NULL;
	}
	model->materials[0].name = stralloc("default");

	/* 读取数据 */
	nummaterials = 0;
	while (fscanf(file, "%s", buf) != EOF) {
		switch (buf[0]) {
		case '#':
			fgets(buf, sizeof(buf), file);
			break;
		case 'n':
			fgets(buf, sizeof(buf), file);
			sscanf(buf, "%s %s", buf, buf);
			nummaterials++;
			model->materials[nummaterials].name = stralloc(buf);
			break;
		case 'N':
			fscanf(file, "%f", &model->materials[nummaterials].shininess);
			/*Ns 10.000 # 范围从0到1000  wavefront shininess is from [0, 1000], so scale for OpenGL */
			model->materials[nummaterials].shininess /= 1000.0;
			model->materials[nummaterials].shininess *= 128.0;
			break;
		case 'm':        /* texture map */
			fgets(buf, sizeof(buf), file);
			sscanf(buf, "%s %s", buf, buf);
			picturefilename = (char*)malloc(sizeof(char) * (strlen(dir) + strlen(buf) + 1));
			strcpy(picturefilename, dir);
			strcat(picturefilename, buf);
			model->materials[nummaterials].map_file = picturefilename;
			//_glmReadPNG(model, textureArray, picturefilename, nummaterials);
			break;
		case 'K':
			switch (buf[1]) {
			case 'd':
				fscanf(file, "%f %f %f",
					&model->materials[nummaterials].diffuse[0],
					&model->materials[nummaterials].diffuse[1],
					&model->materials[nummaterials].diffuse[2]);
				break;
			case 's':
				fscanf(file, "%f %f %f",
					&model->materials[nummaterials].specular[0],
					&model->materials[nummaterials].specular[1],
					&model->materials[nummaterials].specular[2]);
				break;
			case 'a':
				fscanf(file, "%f %f %f",
					&model->materials[nummaterials].ambient[0],
					&model->materials[nummaterials].ambient[1],
					&model->materials[nummaterials].ambient[2]);
				break;
			default:
				/* eat up rest of line */
				fgets(buf, sizeof(buf), file);
				break;
			}
			break;
		default:
			/* eat up rest of line */
			fgets(buf, sizeof(buf), file);
			break;
		}

	}
	free(dir);
}

/* _glmWriteMTL: write a wavefront material library file//写入mtl文件
*
* model      - properly initialized GLMmodel structure
* modelpath  - pathname of the model being written
* mtllibname - name of the material library to be written
*/
static GLvoid _glmWriteMTL(GLMmodel* model, char* modelpath, char* mtllibname)
{
	FILE* file;
	char* dir;
	char* filename;
	GLMmaterial* material;
	GLuint i;

	dir = _glmDirName(modelpath);
	filename = (char*)malloc(sizeof(char) * (strlen(dir) + strlen(mtllibname)));
	strcpy(filename, dir);
	strcat(filename, mtllibname);
	free(dir);

	/* open the file */
	file = fopen(filename, "w");
	if (!file) {
		fprintf(stderr, "_glmWriteMTL() failed: can't open file \"%s\".\n",
			filename);
		exit(1);
	}
	free(filename);

	/* spit out a header */
	fprintf(file, "#  \n");
	fprintf(file, "#  Wavefront MTL generated by GLM library\n");
	fprintf(file, "#  \n");
	fprintf(file, "#  GLM library copyright (C) 1997 by Nate Robins\n");
	fprintf(file, "#  email: ndr@pobox.com\n");
	fprintf(file, "#  www:   http://www.pobox.com/~ndr\n");
	fprintf(file, "#  \n\n");

	for (i = 0; i < model->nummaterials; i++) {
		material = &model->materials[i];
		fprintf(file, "newmtl %s\n", material->name);
		fprintf(file, "Ka %f %f %f\n",
			material->ambient[0], material->ambient[1], material->ambient[2]);
		fprintf(file, "Kd %f %f %f\n",
			material->diffuse[0], material->diffuse[1], material->diffuse[2]);
		fprintf(file, "Ks %f %f %f\n",
			material->specular[0], material->specular[1], material->specular[2]);
		fprintf(file, "Ns %f\n", material->shininess);
		fprintf(file, "\n");
	}
}


//获取模型的相关信息，值读取了数量信息
static GLvoid _glmFirstPass(GLMmodel* model, FILE* file)
{
	GLuint    numvertices;    /* 节点个数 */
	GLuint    numnormals;      /* 向量个数 */
	GLuint    numtexcoords;    /* 纹理坐标 */
	GLuint    numtriangles;    /* 三角形个数 */
	GLMgroup* group;			/* 当前组 */
	unsigned  v, n, t;
	char      buf[128];

	/* 默认组 */
	group = _glmAddGroup(model, "default");

	numvertices = numnormals = numtexcoords = numtriangles = 0;
	while (fscanf(file, "%s", buf) != EOF) {/*从一个流中执行格式化输入,fscanf遇到空格和换行时结束，注意空格时也结束。这与fgets有区别，fgets遇到空格不结束。*/
		switch (buf[0]) {
		case '#':        /* #代表注释 */
			/* 如果文件中的该行，不足bufsize个字符，则读完该行就结束。如若该行（包括最后一个换行符）的字符数超过bufsize-1，则fgets只返回一个不完整的行，但是，缓冲区总是以NULL字符结尾，对fgets的下一次调用会继续读该行。 */
			fgets(buf, sizeof(buf), file);
			break;
		case 'v':        /* 节点，法向量，纹理坐标 */
			switch (buf[1]) {
			case '\0':      /* 是c/c++语言中的字符串结束符 */
				/* fgets函数读取完整行数据 */
				fgets(buf, sizeof(buf), file);
				numvertices++;
				break;
			case 'n':
				fgets(buf, sizeof(buf), file);
				numnormals++;
				break;
			case 't':
				fgets(buf, sizeof(buf), file);
				numtexcoords++;
				break;
			default:
				printf("_glmFirstPass(): Unknown token \"%s\".\n", buf);
				exit(1);
				break;
			}
			break;
		case 'm':
			fgets(buf, sizeof(buf), file);
			sscanf(buf, "%s %s", buf, buf);
			model->mtllibname = stralloc(buf);
			_glmReadMTL(model, buf);
			break;
		case 'u':
			fgets(buf, sizeof(buf), file);
			break;
		case 'g': //组
			fgets(buf, sizeof(buf), file);
			sscanf(buf, "%s", buf);
			group = _glmAddGroup(model, buf);
			break;
		case 'f':
			v = n = t = 0;
			fscanf(file, "%s", buf);
			/* %d, %d//%d, %d/%d, %d/%d/%d %d//%d */
			// fscanf从文件输入，sscanf//从字符串输入；scanf从控制台输入
			if (strstr(buf, "//")) {
				sscanf(buf, "%d//%d", &v, &n);
				fscanf(file, "%d//%d", &v, &n);
				fscanf(file, "%d//%d", &v, &n);
				numtriangles++;
				group->numtriangles++;
				while (fscanf(file, "%d//%d", &v, &n) > 0) {
					numtriangles++;
					group->numtriangles++;
				}
			}
			else if (sscanf(buf, "%d/%d/%d", &v, &t, &n) == 3) {
				/* v/t/n */
				fscanf(file, "%d/%d/%d", &v, &t, &n);
				fscanf(file, "%d/%d/%d", &v, &t, &n);
				numtriangles++;
				group->numtriangles++;
				while (fscanf(file, "%d/%d/%d", &v, &t, &n) > 0) {
					numtriangles++;
					group->numtriangles++;
				}
			}
			else if (sscanf(buf, "%d/%d", &v, &t) == 2) {
				/* v/t */
				fscanf(file, "%d/%d", &v, &t);
				fscanf(file, "%d/%d", &v, &t);
				numtriangles++;
				group->numtriangles++;
				while (fscanf(file, "%d/%d", &v, &t) > 0) {
					numtriangles++;
					group->numtriangles++;
				}
			}
			else {
				/* v */
				fscanf(file, "%d", &v);
				fscanf(file, "%d", &v);
				numtriangles++;
				group->numtriangles++;
				while (fscanf(file, "%d", &v) > 0) {
					numtriangles++;
					group->numtriangles++;
				}
			}
			break;

		default:
			/* eat up rest of line */
			fgets(buf, sizeof(buf), file);
			break;
		}
	}

#if 0
	/* announce the model statistics */
	printf(" Vertices: %d\n", numvertices);
	printf(" Normals: %d\n", numnormals);
	printf(" Texcoords: %d\n", numtexcoords);
	printf(" Triangles: %d\n", numtriangles);
	printf(" Groups: %d\n", model->numgroups);
#endif

	/* set the stats in the model structure */
	model->numvertices = numvertices;
	model->numnormals = numnormals;
	model->numtexcoords = numtexcoords;
	model->numtriangles = numtriangles;


	/* 为组分配内存*/
	group = model->groups;
	while (group) {
		group->triangles = (GLuint*)malloc(sizeof(GLuint) * group->numtriangles);
		group->numtriangles = 0;
		group = group->next;
	}
}

//获取所有的实际数据
static GLvoid _glmSecondPass(GLMmodel* model, FILE* file)
{
	GLuint    numvertices;    /* number of vertices in model */
	GLuint    numnormals;      /* number of normals in model */
	GLuint    numtexcoords;    /* number of texcoords in model */
	GLuint    numtriangles;    /* number of triangles in model */
	GLfloat*  vertices;      /* array of vertices  */
	GLfloat*  normals;      /* array of normals */
	GLfloat*  texcoords;      /* array of texture coordinates */
	GLMgroup* group;      /* current group pointer */
	GLuint    material;      /* current material */
	GLuint    v, n, t;
	char      buf[128];
	GLfloat   tmpYcoord;

	/* set the pointer shortcuts */
	vertices = model->vertices;
	normals = model->normals;
	texcoords = model->texcoords;
	group = model->groups;

	/* 将数据读入到分配好的内存当中 */
	numvertices = numnormals = numtexcoords = 1;
	numtriangles = 0;
	material = 0;
	while (fscanf(file, "%s", buf) != EOF) {
		switch (buf[0]) {
		case '#':/* 注释 */
			fgets(buf, sizeof(buf), file);
			break;
		case 'v':        /* v, vn, vt */
			switch (buf[1]) {
			case '\0':      /* vertex */
				fscanf(file, "%f %f %f",
					&vertices[3 * numvertices + X],
					&vertices[3 * numvertices + Y],
					&vertices[3 * numvertices + Z]);
				numvertices++;
				break;
			case 'n':        /* normal */
				fscanf(file, "%f %f %f",
					&normals[3 * numnormals + X],
					&normals[3 * numnormals + Y],
					&normals[3 * numnormals + Z]);
				numnormals++;
				break;
			case 't':        /* texcoord */
				fscanf(file, "%f %f",
					&texcoords[2 * numtexcoords + X],
					&tmpYcoord);
				texcoords[2 * numtexcoords + Y] = -tmpYcoord;//？？为什么是负值
				numtexcoords++;
				break;
			}
			break;
		case 'u':
			fgets(buf, sizeof(buf), file);
			sscanf(buf, "%s %s", buf, buf);
			group->material = material = _glmFindMaterial(model, buf);
			break;
		case 'g':        /* group */
			fgets(buf, sizeof(buf), file);
			sscanf(buf, "%s", buf);
			group = _glmFindGroup(model, buf);
			group->material = material;
			break;
		case 'f':        /* face */
			v = n = t = 0;
			fscanf(file, "%s", buf);
			/* can be one of %d, %d//%d, %d/%d, %d/%d/%d %d//%d */
			if (strstr(buf, "//")) {
				/* v//n */
				sscanf(buf, "%d//%d", &v, &n);
				T(numtriangles).vindices[0] = v;
				T(numtriangles).nindices[0] = n;
				fscanf(file, "%d//%d", &v, &n);
				T(numtriangles).vindices[1] = v;
				T(numtriangles).nindices[1] = n;
				fscanf(file, "%d//%d", &v, &n);
				T(numtriangles).vindices[2] = v;
				T(numtriangles).nindices[2] = n;
				group->triangles[group->numtriangles++] = numtriangles;
				numtriangles++;
				while (fscanf(file, "%d//%d", &v, &n) > 0) {
					T(numtriangles).vindices[0] = T(numtriangles - 1).vindices[0];
					T(numtriangles).nindices[0] = T(numtriangles - 1).nindices[0];
					T(numtriangles).vindices[1] = T(numtriangles - 1).vindices[2];
					T(numtriangles).nindices[1] = T(numtriangles - 1).nindices[2];
					T(numtriangles).vindices[2] = v;
					T(numtriangles).nindices[2] = n;
					group->triangles[group->numtriangles++] = numtriangles;
					numtriangles++;
				}
			}
			else if (sscanf(buf, "%d/%d/%d", &v, &t, &n) == 3) {
				/* v/t/n */
				T(numtriangles).vindices[0] = v;
				T(numtriangles).tindices[0] = t;
				T(numtriangles).nindices[0] = n;
				fscanf(file, "%d/%d/%d", &v, &t, &n);
				T(numtriangles).vindices[1] = v;
				T(numtriangles).tindices[1] = t;
				T(numtriangles).nindices[1] = n;
				fscanf(file, "%d/%d/%d", &v, &t, &n);
				T(numtriangles).vindices[2] = v;
				T(numtriangles).tindices[2] = t;
				T(numtriangles).nindices[2] = n;
				group->triangles[group->numtriangles++] = numtriangles;
				numtriangles++;
				while (fscanf(file, "%d/%d/%d", &v, &t, &n) > 0) {//如果多于三个点，那么构建新的三角形
					T(numtriangles).vindices[0] = T(numtriangles - 1).vindices[0];
					T(numtriangles).tindices[0] = T(numtriangles - 1).tindices[0];
					T(numtriangles).nindices[0] = T(numtriangles - 1).nindices[0];
					T(numtriangles).vindices[1] = T(numtriangles - 1).vindices[2];
					T(numtriangles).tindices[1] = T(numtriangles - 1).tindices[2];
					T(numtriangles).nindices[1] = T(numtriangles - 1).nindices[2];
					T(numtriangles).vindices[2] = v;
					T(numtriangles).tindices[2] = t;
					T(numtriangles).nindices[2] = n;
					group->triangles[group->numtriangles++] = numtriangles;
					numtriangles++;
				}
			}
			else if (sscanf(buf, "%d/%d", &v, &t) == 2) {
				/* v/t */
				T(numtriangles).vindices[0] = v;
				T(numtriangles).tindices[0] = t;
				fscanf(file, "%d/%d", &v, &t);
				T(numtriangles).vindices[1] = v;
				T(numtriangles).tindices[1] = t;
				fscanf(file, "%d/%d", &v, &t);
				T(numtriangles).vindices[2] = v;
				T(numtriangles).tindices[2] = t;
				group->triangles[group->numtriangles++] = numtriangles;
				numtriangles++;
				while (fscanf(file, "%d/%d", &v, &t) > 0) {
					T(numtriangles).vindices[0] = T(numtriangles - 1).vindices[0];
					T(numtriangles).tindices[0] = T(numtriangles - 1).tindices[0];
					T(numtriangles).vindices[1] = T(numtriangles - 1).vindices[2];
					T(numtriangles).tindices[1] = T(numtriangles - 1).tindices[2];
					T(numtriangles).vindices[2] = v;
					T(numtriangles).tindices[2] = t;
					group->triangles[group->numtriangles++] = numtriangles;
					numtriangles++;
				}
			}
			else {
				/* v */
				sscanf(buf, "%d", &v);
				T(numtriangles).vindices[0] = v;
				fscanf(file, "%d", &v);
				T(numtriangles).vindices[1] = v;
				fscanf(file, "%d", &v);
				T(numtriangles).vindices[2] = v;
				group->triangles[group->numtriangles++] = numtriangles;
				numtriangles++;
				while (fscanf(file, "%d", &v) > 0) {
					T(numtriangles).vindices[0] = T(numtriangles - 1).vindices[0];
					T(numtriangles).vindices[1] = T(numtriangles - 1).vindices[2];
					T(numtriangles).vindices[2] = v;
					group->triangles[group->numtriangles++] = numtriangles;
					numtriangles++;
				}
			}
			break;

		default:
			/* eat up rest of line */
			fgets(buf, sizeof(buf), file);
			break;
		}
	}

#if 0
	/* announce the memory requirements */
	printf(" Memory: %d bytes\n",
		numvertices * 3 * sizeof(GLfloat) +
		numnormals * 3 * sizeof(GLfloat) * (numnormals ? 1 : 0) +
		numtexcoords * 3 * sizeof(GLfloat) * (numtexcoords ? 1 : 0) +
		numtriangles * sizeof(GLMtriangle));
#endif
}

/* public functions */

/* glmUnitize: "unitize" a model by translating it to the origin and
* scaling it to fit in a unit cube around the origin.  Returns the
* scalefactor used.//将模型在指定的范围内显示
*
* model - properly initialized GLMmodel structure
*/
GLfloat glmUnitize(GLMmodel* model, GLfloat center[3])
{
	GLuint  i;
	GLfloat maxx, minx, maxy, miny, maxz, minz;
	GLfloat cx, cy, cz, w, h, d;
	GLfloat scale;

	assert(model);
	assert(model->vertices);

	/* get the max/mins */
	maxx = minx = model->vertices[3 + X];
	maxy = miny = model->vertices[3 + Y];
	maxz = minz = model->vertices[3 + Z];
	for (i = 1; i <= model->numvertices; i++) {
		if (maxx < model->vertices[3 * i + X])
			maxx = model->vertices[3 * i + X];
		if (minx > model->vertices[3 * i + X])
			minx = model->vertices[3 * i + X];

		if (maxy < model->vertices[3 * i + Y])
			maxy = model->vertices[3 * i + Y];
		if (miny > model->vertices[3 * i + Y])
			miny = model->vertices[3 * i + Y];

		if (maxz < model->vertices[3 * i + Z])
			maxz = model->vertices[3 * i + Z];
		if (minz > model->vertices[3 * i + Z])
			minz = model->vertices[3 * i + Z];
	}

	/* 计算宽高深度*/
	w = _glmAbs(maxx) + _glmAbs(minx);
	h = _glmAbs(maxy) + _glmAbs(miny);
	d = _glmAbs(maxz) + _glmAbs(minz);

	/* calculate center of the model */
	cx = (maxx + minx) / 2.0;
	cy = (maxy + miny) / 2.0;
	cz = (maxz + minz) / 2.0;

	/* calculate unitizing scale factor */
	scale = 2.0 / _glmMax(_glmMax(w, h), d);

	/* translate around center then scale */
	for (i = 1; i <= model->numvertices; i++) {
		model->vertices[3 * i + X] -= cx;
		model->vertices[3 * i + Y] -= cy;
		model->vertices[3 * i + Z] -= cz;
		model->vertices[3 * i + X] *= scale;
		model->vertices[3 * i + Y] *= scale;
		model->vertices[3 * i + Z] *= scale;
	}

	center[0] = cx;
	center[1] = cy;
	center[2] = cz;
	return scale;
}

/* glmDimensions: Calculates the dimensions (width, height, depth) of
* a model.计算当前数据的维度，
*
* model      - initialized GLMmodel structure
* dimensions - array of 3 GLfloats (GLfloat dimensions[3])
*/
GLvoid glmDimensions(GLMmodel* model, GLfloat* dimensions)
{
	GLuint i;
	GLfloat maxx, minx, maxy, miny, maxz, minz;

	assert(model);
	assert(model->vertices);
	assert(dimensions);

	/* get the max/mins */
	maxx = minx = model->vertices[3 + X];
	maxy = miny = model->vertices[3 + Y];
	maxz = minz = model->vertices[3 + Z];
	for (i = 1; i <= model->numvertices; i++) {
		if (maxx < model->vertices[3 * i + X])
			maxx = model->vertices[3 * i + X];
		if (minx > model->vertices[3 * i + X])
			minx = model->vertices[3 * i + X];

		if (maxy < model->vertices[3 * i + Y])
			maxy = model->vertices[3 * i + Y];
		if (miny > model->vertices[3 * i + Y])
			miny = model->vertices[3 * i + Y];

		if (maxz < model->vertices[3 * i + Z])
			maxz = model->vertices[3 * i + Z];
		if (minz > model->vertices[3 * i + Z])
			minz = model->vertices[3 * i + Z];
	}

	/* calculate model width, height, and depth */
	dimensions[X] = _glmAbs(maxx) + _glmAbs(minx);
	dimensions[Y] = _glmAbs(maxy) + _glmAbs(miny);
	dimensions[Z] = _glmAbs(maxz) + _glmAbs(minz);
}

/* glmScale: Scales a model by a given amount.缩放全图
*
* model - properly initialized GLMmodel structure
* scale - scalefactor (0.5 = half as large, 2.0 = twice as large)
*/
GLvoid glmScale(GLMmodel* model, GLfloat scale)
{
	GLuint i;

	for (i = 1; i <= model->numvertices; i++) {
		model->vertices[3 * i + X] *= scale;
		model->vertices[3 * i + Y] *= scale;
		model->vertices[3 * i + Z] *= scale;
	}
}

/* glmReverseWinding: Reverse the polygon winding for all polygons in
* this model.  Default winding is counter-clockwise.  Also changes
* the direction of the normals.
*
* model - properly initialized GLMmodel structure
*/
GLvoid glmReverseWinding(GLMmodel* model)
{
	GLuint i, swap;

	assert(model);

	for (i = 0; i < model->numtriangles; i++) {
		swap = T(i).vindices[0];
		T(i).vindices[0] = T(i).vindices[2];
		T(i).vindices[2] = swap;

		if (model->numnormals) {
			swap = T(i).nindices[0];
			T(i).nindices[0] = T(i).nindices[2];
			T(i).nindices[2] = swap;
		}

		if (model->numtexcoords) {
			swap = T(i).tindices[0];
			T(i).tindices[0] = T(i).tindices[2];
			T(i).tindices[2] = swap;
		}
	}

	/* reverse facet normals */
	for (i = 1; i <= model->numfacetnorms; i++) {
		model->facetnorms[3 * i + X] = -model->facetnorms[3 * i + X];
		model->facetnorms[3 * i + Y] = -model->facetnorms[3 * i + Y];
		model->facetnorms[3 * i + Z] = -model->facetnorms[3 * i + Z];
	}

	/* reverse vertex normals */
	for (i = 1; i <= model->numnormals; i++) {
		model->normals[3 * i + X] = -model->normals[3 * i + X];
		model->normals[3 * i + Y] = -model->normals[3 * i + Y];
		model->normals[3 * i + Z] = -model->normals[3 * i + Z];
	}
}

/* glmFacetNormals: Generates facet normals for a model (by taking the
* cross product of the two vectors derived from the sides of each
* triangle).  Assumes a counter-clockwise winding.
*根据每个三角形的边的两个矢量的交叉乘积获得面的向量
* model - initialized GLMmodel structure
*/
GLvoid glmFacetNormals(GLMmodel* model)
{
	GLuint  i;
	GLfloat u[3];
	GLfloat v[3];

	assert(model);
	assert(model->vertices);

	/* 如果存在面向量，那么释放 */
	if (model->facetnorms)
		free(model->facetnorms);

	/* 为面向量分配内存 */
	model->numfacetnorms = model->numtriangles;
	model->facetnorms = (GLfloat*)malloc(sizeof(GLfloat) *
		3 * (model->numfacetnorms + 1));

	for (i = 0; i < model->numtriangles; i++) {
		model->triangles[i].findex = i + 1;
		//根据节点计算向量，节点2减去节点1,
		u[X] = model->vertices[3 * T(i).vindices[1] + X] -
			model->vertices[3 * T(i).vindices[0] + X];
		u[Y] = model->vertices[3 * T(i).vindices[1] + Y] -
			model->vertices[3 * T(i).vindices[0] + Y];
		u[Z] = model->vertices[3 * T(i).vindices[1] + Z] -
			model->vertices[3 * T(i).vindices[0] + Z];
		//节点3减去节点1
		v[X] = model->vertices[3 * T(i).vindices[2] + X] -
			model->vertices[3 * T(i).vindices[0] + X];
		v[Y] = model->vertices[3 * T(i).vindices[2] + Y] -
			model->vertices[3 * T(i).vindices[0] + Y];
		v[Z] = model->vertices[3 * T(i).vindices[2] + Z] -
			model->vertices[3 * T(i).vindices[0] + Z];

		_glmCross(u, v, &model->facetnorms[3 * (i + 1)]);//向量外积，交叉乘积
		_glmNormalize(&model->facetnorms[3 * (i + 1)]);//单位化
	}
}

/* glmVertexNormals: Generates smooth vertex normals for a model.
* First builds a list of all the triangles each vertex is in.  Then
* loops through each vertex in the the list averaging all the facet
* normals of the triangles each vertex is in.  Finally, sets the
* normal index in the triangle for the vertex to the generated smooth
* normal.  If the dot product of a facet normal and the facet normal
* associated with the first triangle in the list of triangles the
* current vertex is in is greater than the cosine of the angle
* parameter to the function, that facet normal is not added into the
* average normal calculation and the corresponding vertex is given
* the facet normal.  This tends to preserve hard edges.  The angle to
* use depends on the model, but 90 degrees is usually a good start.
* 计算节点的向量
* model - initialized GLMmodel structure
* angle - maximum angle (in degrees) to smooth across
*/
GLvoid glmVertexNormals(GLMmodel* model, GLfloat angle)
{
	GLMnode*  node;
	GLMnode*  tail;
	GLMnode** members;
	GLfloat*  normals;
	GLuint    numnormals;
	GLfloat   average[3];
	GLfloat   dot, cos_angle;
	GLuint    i, avg;

	assert(model);
	assert(model->facetnorms);

	/* calculate the cosine of the angle (in degrees) */
	cos_angle = cos(angle * GL_PI / 180.0);

	/* nuke any previous normals */
	if (model->normals)
		free(model->normals);

	/* allocate space for new normals */
	model->numnormals = model->numtriangles * 3; /* 3 normals per triangle */
	model->normals = (GLfloat*)malloc(sizeof(GLfloat) * 3 * (model->numnormals + 1));

	/* allocate a structure that will hold a linked list of triangle
	indices for each vertex */
	members = (GLMnode**)malloc(sizeof(GLMnode*) * (model->numvertices + 1));
	for (i = 1; i <= model->numvertices; i++)
		members[i] = NULL;

	/* for every triangle, create a node for each vertex in it */
	for (i = 0; i < model->numtriangles; i++) {
		node = (GLMnode*)malloc(sizeof(GLMnode));
		node->index = i;
		node->next = members[T(i).vindices[0]];
		members[T(i).vindices[0]] = node;

		node = (GLMnode*)malloc(sizeof(GLMnode));
		node->index = i;
		node->next = members[T(i).vindices[1]];
		members[T(i).vindices[1]] = node;

		node = (GLMnode*)malloc(sizeof(GLMnode));
		node->index = i;
		node->next = members[T(i).vindices[2]];
		members[T(i).vindices[2]] = node;
	}

	/* calculate the average normal for each vertex */
	numnormals = 1;
	for (i = 1; i <= model->numvertices; i++) {
		/* calculate an average normal for this vertex by averaging the
		facet normal of every triangle this vertex is in */
		node = members[i];
		if (!node)
			fprintf(stderr, "glmVertexNormals(): vertex w/o a triangle\n");
		average[0] = 0.0; average[1] = 0.0; average[2] = 0.0;
		avg = 0;
		while (node) {
			/* only average if the dot product of the angle between the two
			facet normals is greater than the cosine of the threshold
			angle -- or, said another way, the angle between the two
			facet normals is less than (or equal to) the threshold angle */
			dot = _glmDot(&model->facetnorms[3 * T(node->index).findex],
				&model->facetnorms[3 * T(members[i]->index).findex]);
			if (dot > cos_angle) {
				node->averaged = GL_TRUE;
				average[0] += model->facetnorms[3 * T(node->index).findex + 0];
				average[1] += model->facetnorms[3 * T(node->index).findex + 1];
				average[2] += model->facetnorms[3 * T(node->index).findex + 2];
				avg = 1;      /* we averaged at least one normal! */
			}
			else {
				node->averaged = GL_FALSE;
			}
			node = node->next;
		}

		if (avg) {
			/* normalize the averaged normal */
			_glmNormalize(average);

			/* add the normal to the vertex normals list */
			model->normals[3 * numnormals + 0] = average[0];
			model->normals[3 * numnormals + 1] = average[1];
			model->normals[3 * numnormals + 2] = average[2];
			avg = numnormals;
			numnormals++;
		}

		/* set the normal of this vertex in each triangle it is in */
		node = members[i];
		while (node) {
			if (node->averaged) {
				/* if this node was averaged, use the average normal */
				if (T(node->index).vindices[0] == i)
					T(node->index).nindices[0] = avg;
				else if (T(node->index).vindices[1] == i)
					T(node->index).nindices[1] = avg;
				else if (T(node->index).vindices[2] == i)
					T(node->index).nindices[2] = avg;
			}
			else
			{
				/* if this node wasn't averaged, use the facet normal */
				model->normals[3 * numnormals + 0] =
					model->facetnorms[3 * T(node->index).findex + 0];
				model->normals[3 * numnormals + 1] =
					model->facetnorms[3 * T(node->index).findex + 1];
				model->normals[3 * numnormals + 2] =
					model->facetnorms[3 * T(node->index).findex + 2];
				if (T(node->index).vindices[0] == i)
					T(node->index).nindices[0] = numnormals;
				else if (T(node->index).vindices[1] == i)
					T(node->index).nindices[1] = numnormals;
				else if (T(node->index).vindices[2] == i)
					T(node->index).nindices[2] = numnormals;
				numnormals++;
			}
			node = node->next;
		}
	}

	model->numnormals = numnormals - 1;

	/* free the member information */
	for (i = 1; i <= model->numvertices; i++) {
		node = members[i];
		while (node) {
			tail = node;
			node = node->next;
			free(tail);
		}
	}
	free(members);

	/* pack the normals array (we previously allocated the maximum
	number of normals that could possibly be created (numtriangles *
	3), so get rid of some of them (usually alot unless none of the
	facet normals were averaged)) */
	normals = model->normals;
	model->normals = (GLfloat*)malloc(sizeof(GLfloat) * 3 * (model->numnormals + 1));
	for (i = 1; i <= model->numnormals; i++) {
		model->normals[3 * i + 0] = normals[3 * i + 0];
		model->normals[3 * i + 1] = normals[3 * i + 1];
		model->normals[3 * i + 2] = normals[3 * i + 2];
	}
	free(normals);

	printf("glmVertexNormals(): %d normals generated\n", model->numnormals);
}

/* glmLinearTexture: Generates texture coordinates according to a
* linear projection of the texture map.  It generates these by
* linearly mapping the vertices onto a square.
*
* model - pointer to initialized GLMmodel structure
*/
GLvoid
glmLinearTexture(GLMmodel* model)
{
	GLMgroup *group;
	GLfloat dimensions[3];
	GLfloat x, y, scalefactor;
	GLuint i;

	assert(model);

	if (model->texcoords)
		free(model->texcoords);
	model->numtexcoords = model->numvertices;
	model->texcoords = (GLfloat*)malloc(sizeof(GLfloat) * 2 * (model->numtexcoords + 1));

	glmDimensions(model, dimensions);
	scalefactor = 2.0 /
		_glmAbs(_glmMax(_glmMax(dimensions[0], dimensions[1]), dimensions[2]));

	/* do the calculations */
	for (i = 1; i <= model->numvertices; i++) {
		x = model->vertices[3 * i + 0] * scalefactor;
		y = model->vertices[3 * i + 2] * scalefactor;
		model->texcoords[2 * i + 0] = (x + 1.0) / 2.0;
		model->texcoords[2 * i + 1] = (y + 1.0) / 2.0;
	}

	/* go through and put texture coordinate indices in all the triangles */
	group = model->groups;
	while (group) {
		for (i = 0; i < group->numtriangles; i++) {
			T(group->triangles[i]).tindices[0] = T(group->triangles[i]).vindices[0];
			T(group->triangles[i]).tindices[1] = T(group->triangles[i]).vindices[1];
			T(group->triangles[i]).tindices[2] = T(group->triangles[i]).vindices[2];
		}
		group = group->next;
	}

#if 0
	printf("glmLinearTexture(): generated %d linear texture coordinates\n",
		model->numtexcoords);
#endif
}

/* glmSpheremapTexture: Generates texture coordinates according to a
* spherical projection of the texture map.  Sometimes referred to as
* spheremap, or reflection map texture coordinates.  It generates
* these by using the normal to calculate where that vertex would map
* onto a sphere.  Since it is impossible to map something flat
* perfectly onto something spherical, there is distortion at the
* poles.  This particular implementation causes the poles along the X
* axis to be distorted.
*
* model - pointer to initialized GLMmodel structure
*/
GLvoid
glmSpheremapTexture(GLMmodel* model)
{
	GLMgroup* group;
	GLfloat theta, phi, rho, x, y, z, r;
	GLuint i;

	assert(model);
	assert(model->normals);

	if (model->texcoords)
		free(model->texcoords);
	model->numtexcoords = model->numnormals;
	model->texcoords = (GLfloat*)malloc(sizeof(GLfloat) * 2 * (model->numtexcoords + 1));

	/* do the calculations */
	for (i = 1; i <= model->numnormals; i++) {
		z = model->normals[3 * i + 0];  /* re-arrange for pole distortion */
		y = model->normals[3 * i + 1];
		x = model->normals[3 * i + 2];
		r = sqrt((x * x) + (y * y));
		rho = sqrt((r * r) + (z * z));

		if (r == 0.0) {
			theta = 0.0;
			phi = 0.0;
		}
		else {
			if (z == 0.0)
				phi = GL_PI / 2.0;
			else
				phi = acos(z / rho);

#if WE_DONT_NEED_THIS_CODE
			if (x == 0.0)
				theta = M_PI / 2.0;  /* asin(y / r); */
			else
				theta = acos(x / r);
#endif

			if (y == 0.0)
				theta = GL_PI / 2.0;  /* acos(x / r); */
			else
				theta = asin(y / r) + (GL_PI / 2.0);
		}

		model->texcoords[2 * i + 0] = theta / GL_PI;
		model->texcoords[2 * i + 1] = phi / GL_PI;
	}

	/* go through and put texcoord indices in all the triangles */
	group = model->groups;
	while (group) {
		for (i = 0; i < group->numtriangles; i++) {
			T(group->triangles[i]).tindices[0] = T(group->triangles[i]).nindices[0];
			T(group->triangles[i]).tindices[1] = T(group->triangles[i]).nindices[1];
			T(group->triangles[i]).tindices[2] = T(group->triangles[i]).nindices[2];
		}
		group = group->next;
	}
}

/* glmDelete: Deletes a GLMmodel structure.
* 删除模型结构
* model - initialized GLMmodel structure
*/
GLvoid glmDelete(GLMmodel* model)
{
	GLMgroup* group;
	GLuint i;

	assert(model);

	if (model->pathname)   free(model->pathname);
	if (model->mtllibname) free(model->mtllibname);
	if (model->vertices)   free(model->vertices);
	if (model->normals)    free(model->normals);
	if (model->texcoords)  free(model->texcoords);
	if (model->facetnorms) free(model->facetnorms);
	if (model->triangles)  free(model->triangles);
	if (model->materials) {
		for (i = 0; i < model->nummaterials; i++)
			free(model->materials[i].name);
	}
	free(model->materials);
	while (model->groups) {
		group = model->groups;
		model->groups = model->groups->next;
		free(group->name);
		free(group->triangles);
		free(group);
	}

	free(model);
}

/* glmReadOBJ: Reads a model description from a Wavefront .OBJ file.
* Returns a pointer to the created object which should be free'd with
* glmDelete().
*
* filename - name of the file containing the Wavefront .OBJ format data.
*/
GLMmodel* glmReadOBJ(char* filename)
{
	GLMmodel* model;
	FILE*     file;

	/* open the file */
	file = fopen(filename, "r");
	if (!file) {
		fprintf(stderr, "glmReadOBJ() failed: can't open data file \"%s\".\n",
			filename);
		exit(1);
	}

	/* 分配内存给新的模型 */
	model = (GLMmodel*)malloc(sizeof(GLMmodel));
	model->pathname = stralloc(filename);
	model->mtllibname = NULL;
	model->numvertices = 0;
	model->vertices = NULL;
	model->numnormals = 0;
	model->normals = NULL;
	model->numtexcoords = 0;
	model->texcoords = NULL;

	model->numfacetnorms = 0;
	model->facetnorms = NULL;
	model->numtriangles = 0;
	model->triangles = NULL;
	model->nummaterials = 0;
	model->materials = NULL;
	model->numgroups = 0;
	model->groups = NULL;
	model->position[0] = 0.0;
	model->position[1] = 0.0;
	model->position[2] = 0.0;

	_glmFirstPass(model, file);

	/* 分配内存 */
	model->vertices = (GLfloat*)malloc(sizeof(GLfloat) *
		3 * (model->numvertices + 1));
	model->triangles = (GLMtriangle*)malloc(sizeof(GLMtriangle) *
		model->numtriangles);
	if (model->numnormals) {
		model->normals = (GLfloat*)malloc(sizeof(GLfloat) *
			3 * (model->numnormals + 1));
	}
	if (model->numtexcoords) {
		model->texcoords = (GLfloat*)malloc(sizeof(GLfloat) *
			2 * (model->numtexcoords + 1));
	}
	/* C 程序中的库函数，功能是将文件内部的指针重新指向一个流的开头*/
	rewind(file);
	_glmSecondPass(model, file);
	/* 释放数据 */
	fclose(file);

	return model;
}

/* glmWriteOBJ: Writes a model description in Wavefront .OBJ format to
* a file.
*
* model    - initialized GLMmodel structure
* filename - name of the file to write the Wavefront .OBJ format data to
* mode     - a bitwise or of values describing what is written to the file
*            GLM_NONE     -  render with only vertices
*            GLM_FLAT     -  render with facet normals
*            GLM_SMOOTH   -  render with vertex normals
*            GLM_TEXTURE  -  render with texture coords
*            GLM_COLOR    -  render with colors (color material)
*            GLM_MATERIAL -  render with materials
*            GLM_COLOR and GLM_MATERIAL should not both be specified.
*            GLM_FLAT and GLM_SMOOTH should not both be specified.
*/
GLvoid glmWriteOBJ(GLMmodel* model, char* filename, GLuint mode)
{
	GLuint    i;
	FILE*     file;
	GLMgroup* group;

	assert(model);

	/* do a bit of warning */
	if (mode & GLM_FLAT && !model->facetnorms) {
		printf("glmWriteOBJ() warning: flat normal output requested "
			"with no facet normals defined.\n");
		mode &= ~GLM_FLAT;
	}
	if (mode & GLM_SMOOTH && !model->normals) {
		printf("glmWriteOBJ() warning: smooth normal output requested "
			"with no normals defined.\n");
		mode &= ~GLM_SMOOTH;
	}
	if (mode & GLM_TEXTURE && !model->texcoords) {
		printf("glmWriteOBJ() warning: texture coordinate output requested "
			"with no texture coordinates defined.\n");
		mode &= ~GLM_TEXTURE;
	}
	if (mode & GLM_FLAT && mode & GLM_SMOOTH) {
		printf("glmWriteOBJ() warning: flat normal output requested "
			"and smooth normal output requested (using smooth).\n");
		mode &= ~GLM_FLAT;
	}

	/* open the file */
	file = fopen(filename, "w");
	if (!file) {
		fprintf(stderr, "glmWriteOBJ() failed: can't open file \"%s\" to write.\n",
			filename);
		exit(1);
	}

	/* spit out a header */
	fprintf(file, "#  \n");
	fprintf(file, "#  Wavefront OBJ generated by GLM library\n");
	fprintf(file, "#  \n");
	fprintf(file, "#  GLM library copyright (C) 1997 by Nate Robins\n");
	fprintf(file, "#  email: ndr@pobox.com\n");
	fprintf(file, "#  www:   http://www.pobox.com/~ndr\n");
	fprintf(file, "#  \n");

	if (mode & GLM_MATERIAL && model->mtllibname) {
		fprintf(file, "\nmtllib %s\n\n", model->mtllibname);
		_glmWriteMTL(model, filename, model->mtllibname);
	}

	/* spit out the vertices */
	fprintf(file, "\n");
	fprintf(file, "# %d vertices\n", model->numvertices);
	for (i = 1; i <= model->numvertices; i++) {
		fprintf(file, "v %f %f %f\n",
			model->vertices[3 * i + 0],
			model->vertices[3 * i + 1],
			model->vertices[3 * i + 2]);
	}

	/* spit out the smooth/flat normals */
	if (mode & GLM_SMOOTH) {
		fprintf(file, "\n");
		fprintf(file, "# %d normals\n", model->numnormals);
		for (i = 1; i <= model->numnormals; i++) {
			fprintf(file, "vn %f %f %f\n",
				model->normals[3 * i + 0],
				model->normals[3 * i + 1],
				model->normals[3 * i + 2]);
		}
	}
	else if (mode & GLM_FLAT) {
		fprintf(file, "\n");
		fprintf(file, "# %d normals\n", model->numfacetnorms);
		for (i = 1; i <= model->numnormals; i++) {
			fprintf(file, "vn %f %f %f\n",
				model->facetnorms[3 * i + 0],
				model->facetnorms[3 * i + 1],
				model->facetnorms[3 * i + 2]);
		}
	}

	/* spit out the texture coordinates */
	if (mode & GLM_TEXTURE) {
		fprintf(file, "\n");
		fprintf(file, "# %d texcoords\n", model->numtexcoords); // ypchui@20070522: texcoords -> numtexcoords
		for (i = 1; i <= model->numtexcoords; i++) {
			fprintf(file, "vt %f %f\n",
				model->texcoords[2 * i + 0],
				model->texcoords[2 * i + 1]);
		}
	}

	fprintf(file, "\n");
	fprintf(file, "# %d groups\n", model->numgroups);
	fprintf(file, "# %d faces (triangles)\n", model->numtriangles);
	fprintf(file, "\n");

	group = model->groups;
	while (group) {
		fprintf(file, "g %s\n", group->name);
		if (mode & GLM_MATERIAL)
			fprintf(file, "usemtl %s\n", model->materials[group->material].name);
		for (i = 0; i < group->numtriangles; i++) {
			if (mode & GLM_SMOOTH && mode & GLM_TEXTURE) {
				fprintf(file, "f %d/%d/%d %d/%d/%d %d/%d/%d\n",
					T(group->triangles[i]).vindices[0],
					T(group->triangles[i]).nindices[0],
					T(group->triangles[i]).tindices[0],
					T(group->triangles[i]).vindices[1],
					T(group->triangles[i]).nindices[1],
					T(group->triangles[i]).tindices[1],
					T(group->triangles[i]).vindices[2],
					T(group->triangles[i]).nindices[2],
					T(group->triangles[i]).tindices[2]);
			}
			else if (mode & GLM_FLAT && mode & GLM_TEXTURE) {
				fprintf(file, "f %d/%d %d/%d %d/%d\n",
					T(group->triangles[i]).vindices[0],
					T(group->triangles[i]).findex,
					T(group->triangles[i]).vindices[1],
					T(group->triangles[i]).findex,
					T(group->triangles[i]).vindices[2],
					T(group->triangles[i]).findex);
			}
			else if (mode & GLM_TEXTURE) {
				fprintf(file, "f %d/%d %d/%d %d/%d\n",
					T(group->triangles[i]).vindices[0],
					T(group->triangles[i]).tindices[0],
					T(group->triangles[i]).vindices[1],
					T(group->triangles[i]).tindices[1],
					T(group->triangles[i]).vindices[2],
					T(group->triangles[i]).tindices[2]);
			}
			else if (mode & GLM_SMOOTH) {
				fprintf(file, "f %d//%d %d//%d %d//%d\n",
					T(group->triangles[i]).vindices[0],
					T(group->triangles[i]).nindices[0],
					T(group->triangles[i]).vindices[1],
					T(group->triangles[i]).nindices[1],
					T(group->triangles[i]).vindices[2],
					T(group->triangles[i]).nindices[2]);
			}
			else if (mode & GLM_FLAT) {
				fprintf(file, "f %d//%d %d//%d %d//%d\n",
					T(group->triangles[i]).vindices[0],
					T(group->triangles[i]).findex,
					T(group->triangles[i]).vindices[1],
					T(group->triangles[i]).findex,
					T(group->triangles[i]).vindices[2],
					T(group->triangles[i]).findex);
			}
			else {
				fprintf(file, "f %d %d %d\n",
					T(group->triangles[i]).vindices[0],
					T(group->triangles[i]).vindices[1],
					T(group->triangles[i]).vindices[2]);
			}
		}
		fprintf(file, "\n");
		group = group->next;
	}

	fclose(file);
}

/* glmDraw: Renders the model to the current OpenGL context using the
* mode specified.
*
* model    - initialized GLMmodel structure
* mode     - a bitwise OR of values describing what is to be rendered.
*            GLM_NONE     -  render with only vertices 只渲染节点
*            GLM_FLAT     -  render with facet normals 面向量渲染
*            GLM_SMOOTH   -  render with vertex normals 节点向量渲染
*            GLM_TEXTURE  -  render with texture coords 渲染文本
*            GLM_COLOR    -  render with colors (color material) 渲染颜色
*            GLM_MATERIAL -  render with materials 渲染材质
*            GLM_COLOR and GLM_MATERIAL should not both be specified.
*            GLM_FLAT and GLM_SMOOTH should not both be specified.
*/
GLvoid glmDraw(GLMmodel* model, GLuint mode)
{
	GLuint i;
	GLMgroup* group;

	assert(model);
	assert(model->vertices);

	/* do a bit of warning */
	if (mode & GLM_FLAT && !model->facetnorms) {
		printf("glmDraw() warning: flat render mode requested "
			"with no facet normals defined.\n");
		mode &= ~GLM_FLAT;
	}
	if (mode & GLM_SMOOTH && !model->normals) {
		printf("glmDraw() warning: smooth render mode requested "
			"with no normals defined.\n");
		mode &= ~GLM_SMOOTH;
	}
	if (mode & GLM_TEXTURE && !model->texcoords) {
		printf("glmDraw() warning: texture render mode requested "
			"with no texture coordinates defined.\n");
		mode &= ~GLM_TEXTURE;
	}
	if (mode & GLM_FLAT && mode & GLM_SMOOTH) {
		printf("glmDraw() warning: flat render mode requested "
			"and smooth render mode requested (using smooth).\n");
		mode &= ~GLM_FLAT;
	}
	if (mode & GLM_COLOR && !model->materials) {
		printf("glmDraw() warning: color render mode requested "
			"with no materials defined.\n");
		mode &= ~GLM_COLOR;
	}
	if (mode & GLM_MATERIAL && !model->materials) {
		printf("glmDraw() warning: material render mode requested "
			"with no materials defined.\n");
		mode &= ~GLM_MATERIAL;
	}
	if (mode & GLM_COLOR && mode & GLM_MATERIAL) {
		printf("glmDraw() warning: color and material render mode requested "
			"using only material mode\n");
		mode &= ~GLM_COLOR;
	}
	if (mode & GLM_COLOR)
		glEnable(GL_COLOR_MATERIAL);
	if (mode & GLM_MATERIAL)
		glDisable(GL_COLOR_MATERIAL);

	glPushMatrix();
	glTranslatef(model->position[0], model->position[1], model->position[2]);

	group = model->groups;
	while (group) {
		if (mode & GLM_MATERIAL) {
			glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT,
				model->materials[group->material].ambient);
			glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE,
				model->materials[group->material].diffuse);
			glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR,
				model->materials[group->material].specular);
			glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS,
				model->materials[group->material].shininess);
		}

		if (mode & GLM_COLOR) {
			glColor3fv(model->materials[group->material].diffuse);
		}

		/* add code here to bind texture for each model */
		if (mode & GLM_TEXTURE) {
			glEnable(GL_TEXTURE_2D);
			glBindTexture(GL_TEXTURE_2D, textureArray[group->material]);
		}
		glBegin(GL_TRIANGLES);
		for (i = 0; i < group->numtriangles; i++) {
			if (mode & GLM_FLAT)
				glNormal3fv(&model->facetnorms[3 * T(group->triangles[i]).findex]);

			if (mode & GLM_SMOOTH)
				glNormal3fv(&model->normals[3 * T(group->triangles[i]).nindices[0]]);
			if (mode & GLM_TEXTURE)
				glTexCoord2fv(&model->texcoords[2 * T(group->triangles[i]).tindices[0]]);
			glVertex3fv(&model->vertices[3 * T(group->triangles[i]).vindices[0]]);
#if 0
			printf("%f %f %f\n",
				model->vertices[3 * T(group->triangles[i]).vindices[0] + X],
				model->vertices[3 * T(group->triangles[i]).vindices[0] + Y],
				model->vertices[3 * T(group->triangles[i]).vindices[0] + Z]);
#endif

			if (mode & GLM_SMOOTH)
				glNormal3fv(&model->normals[3 * T(group->triangles[i]).nindices[1]]);
			if (mode & GLM_TEXTURE)
				glTexCoord2fv(&model->texcoords[2 * T(group->triangles[i]).tindices[1]]);
			glVertex3fv(&model->vertices[3 * T(group->triangles[i]).vindices[1]]);
#if 0
			printf("%f %f %f\n",
				model->vertices[3 * T(group->triangles[i]).vindices[1] + X],
				model->vertices[3 * T(group->triangles[i]).vindices[1] + Y],
				model->vertices[3 * T(group->triangles[i]).vindices[1] + Z]);
#endif

			if (mode & GLM_SMOOTH)
				glNormal3fv(&model->normals[3 * T(group->triangles[i]).nindices[2]]);
			if (mode & GLM_TEXTURE)
				glTexCoord2fv(&model->texcoords[2 * T(group->triangles[i]).tindices[2]]);
			glVertex3fv(&model->vertices[3 * T(group->triangles[i]).vindices[2]]);
#if 0
			printf("%f %f %f\n",
				model->vertices[3 * T(group->triangles[i]).vindices[2] + X],
				model->vertices[3 * T(group->triangles[i]).vindices[2] + Y],
				model->vertices[3 * T(group->triangles[i]).vindices[2] + Z]);
#endif

		}
		glEnd();

		group = group->next;
	}

	glPopMatrix();
}

/* glmList: Generates and returns a display list for the model using
* the mode specified.
*
* model    - initialized GLMmodel structure
* mode     - a bitwise OR of values describing what is to be rendered.
*            GLM_NONE     -  render with only vertices
*            GLM_FLAT     -  render with facet normals
*            GLM_SMOOTH   -  render with vertex normals
*            GLM_TEXTURE  -  render with texture coords
*            GLM_COLOR    -  render with colors (color material)
*            GLM_MATERIAL -  render with materials
*            GLM_COLOR and GLM_MATERIAL should not both be specified.
*            GLM_FLAT and GLM_SMOOTH should not both be specified.
*/
GLuint
glmList(GLMmodel* model, GLuint mode)
{
	GLuint list;

	list = glGenLists(1);
	glNewList(list, GL_COMPILE);
	glmDraw(model, mode);
	glEndList();

	return list;
}