/*     *  GLM library.  Wavefront .obj file format reader/writer/manipulator. * *  Written by Nate Robins, 1997. *  email: ndr@pobox.com *  www: http://www.pobox.com/~ndr *//* includes */#include <GL/glut.h>#ifndef M_PI#define M_PI 3.14159265#endif/* defines */#define GLM_NONE     (0)		/* render with only vertices */#define GLM_FLAT     (1 << 0)		/* render with facet normals */#define GLM_SMOOTH   (1 << 1)		/* render with vertex normals */#define GLM_TEXTURE  (1 << 2)		/* render with texture coords */#define GLM_COLOR    (1 << 3)		/* render with colors */#define GLM_MATERIAL (1 << 4)		/* render with materials *//* structs *//* GLMmaterial: Structure that defines a material in a model.  */typedef struct _GLMmaterial{  char* name;				/* name of material */  GLfloat diffuse[4];			/* diffuse component */  GLfloat ambient[4];			/* ambient component */  GLfloat specular[4];			/* specular component */  GLfloat emmissive[4];			/* emmissive component */  GLfloat shininess;			/* specular exponent */} GLMmaterial;/* GLMtriangle: Structure that defines a triangle in a model. */typedef struct {  GLuint vindices[3];			/* array of triangle vertex indices */  GLuint nindices[3];			/* array of triangle normal indices */  GLuint tindices[3];			/* array of triangle texcoord indices*/  GLuint findex;			/* index of triangle facet normal */} GLMtriangle;/* GLMgroup: Structure that defines a group in a model. */typedef struct _GLMgroup {  char*             name;		/* name of this group */  GLuint            numtriangles;	/* number of triangles in this group */  GLuint*           triangles;		/* array of triangle indices */  GLuint            material;           /* index to material for group */  struct _GLMgroup* next;		/* pointer to next group in model */} GLMgroup;/* GLMmodel: Structure that defines a model. */typedef struct {  char*    pathname;			/* path to this model */  char*    mtllibname;			/* name of the material library */  GLuint   numvertices;			/* number of vertices in model */  GLfloat* vertices;			/* array of vertices  */  GLuint   numnormals;			/* number of normals in model */  GLfloat* normals;			/* array of normals */  GLuint   numtexcoords;		/* number of texcoords in model */  GLfloat* texcoords;			/* array of texture coordinates */  GLuint   numfacetnorms;		/* number of facetnorms in model */  GLfloat* facetnorms;			/* array of facetnorms */  GLuint       numtriangles;		/* number of triangles in model */  GLMtriangle* triangles;		/* array of triangles */  GLuint       nummaterials;		/* number of materials in model */  GLMmaterial* materials;		/* array of materials */  GLuint       numgroups;		/* number of groups in model */  GLMgroup*    groups;			/* linked list of groups */  GLfloat position[3];			/* position of the model */} GLMmodel;/* 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. * * model - properly initialized GLMmodel structure  */GLfloatglmUnitize(GLMmodel* model);/* glmDimensions: Calculates the dimensions (width, height, depth) of * a model. * * model      - initialized GLMmodel structure * dimensions - array of 3 GLfloats (GLfloat dimensions[3]) */GLvoidglmDimensions(GLMmodel* model, GLfloat* dimensions);/* glmScale: Scales a model by a given amount. *  * model - properly initialized GLMmodel structure * scale - scalefactor (0.5 = half as large, 2.0 = twice as large) */GLvoidglmScale(GLMmodel* model, GLfloat 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  */GLvoidglmReverseWinding(GLMmodel* model);/* 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. * * model - initialized GLMmodel structure */GLvoidglmFacetNormals(GLMmodel* model);/* 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. * * model - initialized GLMmodel structure * angle - maximum angle (in degrees) to smooth across */GLvoidglmVertexNormals(GLMmodel* model, GLfloat angle);/* 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 */GLvoidglmLinearTexture(GLMmodel* model);/* 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 */GLvoidglmSpheremapTexture(GLMmodel* model);/* glmDelete: Deletes a GLMmodel structure. * * model - initialized GLMmodel structure */GLvoidglmDelete(GLMmodel* 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);/* 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    -  write only vertices *            GLM_FLAT    -  write facet normals *            GLM_SMOOTH  -  write vertex normals *            GLM_TEXTURE -  write texture coords *            GLM_FLAT and GLM_SMOOTH should not both be specified. */GLvoidglmWriteOBJ(GLMmodel* model, char* filename, GLuint mode);/* 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 *            GLM_FLAT    -  render with facet normals *            GLM_SMOOTH  -  render with vertex normals *            GLM_TEXTURE -  render with texture coords *            GLM_FLAT and GLM_SMOOTH should not both be specified. */GLvoidglmDraw(GLMmodel* model, GLuint mode);/* 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_FLAT and GLM_SMOOTH should not both be specified.   */GLuintglmList(GLMmodel* model, GLuint mode);/* 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) * */GLvoidglmWeld(GLMmodel* model, GLfloat epsilon);