OpenGL实例：三角形

OpenGL实例：三角形

作者：凯鲁嘎吉 - 博客园 http://www.cnblogs.com/kailugaji/

更多请查看：计算机图形学

1. 三角形的旋转

 #include <GL/glut.h>
 typedef GLfloat point2d[]; // a point data type
 void triangle(point2d a, point2d b, point2d c) // display a triangle
 {
     glBegin(GL_TRIANGLES);
     glVertex2fv(a);
     glVertex2fv(b);
     glVertex2fv(c);
     glEnd();
 }
 void display(void)
 {
     point2d v[] = { {-1.0, -0.58}, {1.0, -0.58}, {0.0, 1.15} }; //initial triangle vertices
     glClear(GL_COLOR_BUFFER_BIT); // Clear display window
     glColor3f(0.0, 0.0, 1.0); // Set fill color to blue
     glLoadIdentity();//应该放在此处，保证每次显示正确
     glViewport(, , , ); // Set left viewport
     triangle(v[], v[], v[]);
     glColor3f(1.0, 0.0, 0.0); // Set fill color to red
     glViewport(, , , ); // Set right viewport
     glRotatef(90.0, 0.0, 0.0, 1.0); // Rotate about z axis
     triangle(v[], v[], v[]); // Display blue triangle
     glFlush();
 }
 void init()
 {
     glMatrixMode(GL_PROJECTION);
     //glLoadIdentity();//如果放在此处，会导致第一次显示正确，再次刷新时图形旋转
     gluOrtho2D(-2.0, 2.0, -2.0, 2.0);
     glMatrixMode(GL_MODELVIEW);
     glClearColor(1.0, 1.0, 1.0, 1.0);
 }
 void main(int argc, char **argv)
 {
     glutInit(&argc, argv);
     glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
     glutInitWindowSize(, );
     glutCreateWindow("Triangle");
     glutDisplayFunc(display);
     init();
     glutMainLoop();
 }

参考网址：Opengl编程实例－红蓝三角形 - 图形学与可视化 - CSDN博客

2. Sierpinski gasket

方法1：非递归

 #include <cstdlib>
 #include <gl\glut.h>
 class GLintPoint
 {
 public:
     GLint x;
     GLint y;
     GLintPoint(GLint a, GLint b) {
         x = a;
         y = b;
     }
 };
 void myInit(void)
 {
     glClearColor(0.0, 0.0, 0.0, 0.0);
     glColor3f(1.0, 0.0, 0.0);
     glPointSize(2.0);
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
     gluOrtho2D(0.0, 600.0, 0.0, 600.0);
 }
 void drawDot(GLint x, GLint y) {
     glBegin(GL_POINTS);
     glVertex2i(x, y);
     glEnd();
 }
 void myDisplay() {
     glClear(GL_COLOR_BUFFER_BIT);
     GLintPoint T[] = { GLintPoint(, ), GLintPoint(, ), GLintPoint(, ) };
     int index = rand() % ;
     GLintPoint point = T[index];
     drawDot(point.x, point.y);
     for (int i = ; i < ; i++) {
         index = rand() % ;
         point.x = (point.x + T[index].x) / ;
         point.y = (point.y + T[index].y) / ;
         drawDot(point.x, point.y);
     }
     glFlush();
 }
 int main(int argc, char *argv[])
 {
     glutInit(&argc, argv);
     glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
     glutInitWindowPosition(, );
     glutInitWindowSize(, );
     glutCreateWindow("Sierphiski gasket");
     glutDisplayFunc(&myDisplay);
     myInit();
     glutMainLoop();
     return ;
 }

方法2：递归

 #include <GL/glut.h>
 #include<stdlib.h>
 /* initial triangle */
 GLfloat v[][] = { {10.0, 10.0}, {600.0, 10.0}, {300.0, 600.0} };
 int n;
 void triangle(GLfloat *a, GLfloat *b, GLfloat *c)
 /* display one triangle  */
 {
     glVertex2fv(a);
     glVertex2fv(b);
     glVertex2fv(c);
 }
 void divide_triangle(GLfloat  *a, GLfloat *b, GLfloat *c, int m)
 {
     /* triangle subdivision using vertex numbers */
     GLfloat v0[], v1[], v2[];
     int j;
     if (m > )
     {
         for (j = ; j < ; j++) v0[j] = (a[j] + b[j]) / ;
         for (j = ; j < ; j++) v1[j] = (a[j] + c[j]) / ;
         for (j = ; j < ; j++) v2[j] = (b[j] + c[j]) / ;
         divide_triangle(a, v0, v1, m - );
         divide_triangle(c, v1, v2, m - );
         divide_triangle(b, v2, v0, m - );
     }
     else triangle(a, b, c); /* draw triangle at end of recursion */
 }
 void display(void)
 {
     glClear(GL_COLOR_BUFFER_BIT);
     glBegin(GL_TRIANGLES);
     divide_triangle(v[], v[], v[], n);
     glEnd();
     glFlush();
 }
 void myinit()
 {
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
     gluOrtho2D(0.0, 600.0, 0.0, 600.0);
     glMatrixMode(GL_MODELVIEW);
     glClearColor(0.0, 0.0, 0.0, 0.0);
     glColor3f(1.0, 0.0, 0.0);
 }
 void  main(int argc, char **argv)
 {
     n = ;
     glutInit(&argc, argv);
     glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
     glutInitWindowSize(, );
     glutCreateWindow("Sierpinski Gasket");
     glutDisplayFunc(display);
     myinit();
     glutMainLoop();

 }