《交互式计算机图形学》书中附带的示例程序：polygon.c
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/* polygon modeler */
#define MAX_POLYGONS 8
#define MAX_VERTICES 10
typedef int bool;
#define TRUE 1
#define FALSE 0
#include <stdlib.h>
#include <stdio.h>
//#include <GL/glut.h>
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
void myMouse(int,int, int, int);
void myMotion(int, int);
void myDisplay();
void myReshape(int, int);
void color_menu(int);
void main_menu(int);
int pick_polygon(int x, int y);
void myinit();
/* globals */
/* polygon struct */
typedef struct polygon
{
int color; /* color index */
bool used; /* TRUE if polygon exists */
int xmin, xmax, ymin, ymax; /* bounding box */
float xc, yc; /* center of polygon */
int nvertices; /* number of vertices */
int x[MAX_VERTICES]; /* vertices */
int y[MAX_VERTICES];
} polygon;
/* flags */
bool picking = FALSE; /* true while picking */
bool moving = FALSE; /* true while moving polygon */
int in_polygon = -1; /* not in any polygon */
int present_color = 0; /* default color */
GLsizei wh = 500, ww = 500; /* initial window size */
int draw_mode = 0; /* drawing mode */
GLfloat colors[8][3]={{0.0, 0.0, 0.0}, {1.0, 0.0, 0.0},{0.0, 1.0, 0.0},
{0.0, 0.0, 1.0}, {0.0, 1.0, 1.0}, {1.0, 0.0, 1.0}, {1.0, 1.0, 0.0},
{1.0, 1.0, 1.0}};
polygon polygons[MAX_POLYGONS];
void myReshape(int w, int h)
{
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, (GLdouble)w, 0.0, (GLdouble)h);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glViewport(0,0,w,h);
ww = w;
wh = h;
}
void myinit()
{
int i;
/* set clear color to grey */
glClearColor(0.5, 0.5, 0.5, 1.0);
/* mark all polygons unused */
for(i = 0; i<MAX_POLYGONS; i++) polygons[i].used = FALSE;
}
void myMouse(int btn, int state, int x, int y)
{
int i,j;
y = wh-y;
if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN &&!picking&&!moving)
/* adding vertices */
{
moving = FALSE;
if(in_polygon>=0)
{
if(polygons[in_polygon].nvertices == MAX_VERTICES)
{
printf("exceeds maximum number vertices\n");
exit(0);
}
i = polygons[in_polygon].nvertices;
polygons[in_polygon].x[i] = x;
polygons[in_polygon].y[i] = y;
polygons[in_polygon].nvertices++;
}
}
if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN &&picking&&!moving)
{
/* delete polygon */
picking = FALSE;
moving = FALSE;
j = pick_polygon(x,y);
if(j >= 0)
{
polygons[j].used = FALSE;
in_polygon = -1;
glutPostRedisplay();
}
}
}
int pick_polygon(int x, int y)
{
/* find first polygon in which we are in bounding box */
int i;
for(i=0; i<MAX_POLYGONS; i++)
{
if(polygons[i].used)
if((x>=polygons[i].xmin)&&(x<=polygons[i].xmax)&&(y>=polygons[i].ymin)&&(y<polygons[i].ymax))
{
in_polygon = i;
moving = TRUE;
return(i);
}
printf("not in a polygon\n");
return(-1);
}
}
void myMotion(int x, int y)
{
/* find if we are inside a polugon */
float dx, dy;
int i,j;
if(moving)
{
y = wh - y;
j = pick_polygon(x, y);
if(j<0)
{
printf("not in a polygon\n");
return;
}
/* if inside then move polygon */
dx = x - polygons[j].xc;
dy = y - polygons[j].yc;
for(i = 0; i< polygons[j].nvertices; i++)
{
polygons[j].x[i] += dx;
polygons[j].y[i] += dy;
}
/* update bounding box */
polygons[j].xc += dx;
polygons[j].yc += dy;
if(dx>0) polygons[j].xmax += dx;
else polygons[j].xmin += dx;
if(dy>0) polygons[j].ymax += dy;
else polygons[j].ymin += dy;
glutPostRedisplay();
}
}
void color_menu(int index)
{
present_color = index;
if(in_polygon>=0) polygons[in_polygon].color = index;
}
void main_menu(int index)
{
int i;
switch(index)
{
case(1): /* create a new polygon */
{
moving = FALSE;
for(i=0; i<MAX_POLYGONS; i++) if(polygons[i].used == FALSE) break;
if(i == MAX_POLYGONS)
{
printf("exceeeded maximum number of polygons\n");
exit(0);
}
polygons[i].color = present_color;
polygons[i].used = TRUE;
polygons[i].nvertices = 0;
in_polygon = i;
picking = FALSE;
break;
}
case(2): /* end polygon and find bounding box and center */
{
moving = FALSE;
if(in_polygon>=0)
{
polygons[in_polygon].xmax = polygons[in_polygon].xmin = polygons[in_polygon].x[0];
polygons[in_polygon].ymax = polygons[in_polygon].ymin = polygons[in_polygon].y[0];
polygons[in_polygon].xc = polygons[in_polygon].x[0];
polygons[in_polygon].yc = polygons[in_polygon].y[0];
for(i=1;i<polygons[in_polygon].nvertices;i++)
{
if(polygons[in_polygon].x[i]<polygons[in_polygon].xmin)
polygons[in_polygon].xmin = polygons[in_polygon].x[i];
else if(polygons[in_polygon].x[i]>polygons[in_polygon].xmax)
polygons[in_polygon].xmax = polygons[in_polygon].x[i];
if(polygons[in_polygon].y[i]<polygons[in_polygon].ymin)
polygons[in_polygon].ymin = polygons[in_polygon].y[i];
else if(polygons[in_polygon].y[i]>polygons[in_polygon].ymax)
polygons[in_polygon].ymax = polygons[in_polygon].y[i];
polygons[in_polygon].xc += polygons[in_polygon].x[i];
polygons[in_polygon].yc += polygons[in_polygon].y[i];
}
polygons[in_polygon].xc = polygons[in_polygon].xc/polygons[in_polygon].nvertices;
polygons[in_polygon].yc = polygons[in_polygon].yc/polygons[in_polygon].nvertices;
}
in_polygon = -1;
glutPostRedisplay();
break;
}
case(3): /* set picking mode */
{
picking = TRUE;
moving = FALSE;
break;
}
case(4): /* set moving mode */
{
moving = TRUE;
break;
}
case(5): /* exit */
{
exit(0);
break;
}
}
}
void myDisplay()
{
/* display all active polygons */
int i, j;
glClear(GL_COLOR_BUFFER_BIT);
for(i=0; i<MAX_POLYGONS; i++)
{
if(polygons[i].used)
{
glColor3fv(colors[polygons[i].color]);
glBegin(GL_POLYGON);
for(j=0; j<polygons[i].nvertices; j++) glVertex2i(polygons[i].x[j], polygons[i].y[j]);
glEnd();
}
}
glFlush();
}
int main(int argc, char** argv)
{
int c_menu;
glutInit(&argc,argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(500, 500);
glutCreateWindow("polygon modeler");
glutDisplayFunc(myDisplay);
myinit ();
c_menu = glutCreateMenu(color_menu);
glutAddMenuEntry("Black",0);
glutAddMenuEntry("Red",1);
glutAddMenuEntry("Green",2);
glutAddMenuEntry("Blue",3);
glutAddMenuEntry("Cyan",4);
glutAddMenuEntry("Magenta",5);
glutAddMenuEntry("Yellow",6);
glutAddMenuEntry("White",7);
glutCreateMenu(main_menu);
glutAddMenuEntry("new polygon", 1);
glutAddMenuEntry("end polygon", 2);
glutAddMenuEntry("delete polygon", 3);
glutAddMenuEntry("move polygon", 4);
glutAddMenuEntry("quit",5);
glutAddSubMenu("Colors", c_menu);
glutAttachMenu(GLUT_MIDDLE_BUTTON);
glutReshapeFunc (myReshape);
glutMouseFunc (myMouse);
glutMotionFunc(myMotion);
glutMainLoop();
}
首先新建了一个Win32控制台应用程序，空白项目，将该文件添加到资源文件。直接编译会出错，需要修改项目属性，如下设置：
1.工程属性->配置（设为‘所有配置’）->配置属性->C/C++->预处理器定义(设为‘GLUT_BUILDING_LIB’)
2.工程属性->配置（设为‘活动(Debug)’）->链接器->系统->子系统(设为‘控制台(/SUBSYSTEM:CONSOLE)’)——此处不必修改，本身是Win32控制台程序
3.链接器->输入->附加依赖项中添加
glu32.lib
glut32.lib
glut.lib
opengl32.lib
glaux.lib
确定。
4.属性->配置（设为‘所有配置’）->配置属性->C/C++->高级->编译为设置为默认值或编译为C语言
该项目介绍了拾取的相关知识，还要好好学习一下，鼠标中键点击弹出菜单。
http://www.cnblogs.com/cjyang/archive/2010/10/21/1855169.html