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
1 #include <GL/glut.h> 2 typedef GLfloat point2d[2]; // a point data type 3 void triangle(point2d a, point2d b, point2d c) // display a triangle 4 { 5 glBegin(GL_TRIANGLES); 6 glVertex2fv(a); 7 glVertex2fv(b); 8 glVertex2fv(c); 9 glEnd(); 10 } 11 void display(void) 12 { 13 point2d v[3] = { {-1.0, -0.58}, {1.0, -0.58}, {0.0, 1.15} }; //initial triangle vertices 14 glClear(GL_COLOR_BUFFER_BIT); // Clear display window 15 glColor3f(0.0, 0.0, 1.0); // Set fill color to blue 16 glLoadIdentity();//应该放在此处，保证每次显示正确 17 glViewport(0, 0, 300, 400); // Set left viewport 18 triangle(v[0], v[1], v[2]); 19 glColor3f(1.0, 0.0, 0.0); // Set fill color to red 20 glViewport(300, 0, 300, 400); // Set right viewport 21 glRotatef(90.0, 0.0, 0.0, 1.0); // Rotate about z axis 22 triangle(v[0], v[1], v[2]); // Display blue triangle 23 glFlush(); 24 } 25 void init() 26 { 27 glMatrixMode(GL_PROJECTION); 28 //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 29 gluOrtho2D(-2.0, 2.0, -2.0, 2.0); 30 glMatrixMode(GL_MODELVIEW); 31 glClearColor(1.0, 1.0, 1.0, 1.0); 32 } 33 void main(int argc, char **argv) 34 { 35 glutInit(&argc, argv); 36 glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); 37 glutInitWindowSize(600, 400); 38 glutCreateWindow("Triangle"); 39 glutDisplayFunc(display); 40 init(); 41 glutMainLoop(); 42 }
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
1 #include <cstdlib> 2 #include <glglut.h> 3 class GLintPoint 4 { 5 public: 6 GLint x; 7 GLint y; 8 GLintPoint(GLint a, GLint b) { 9 x = a; 10 y = b; 11 } 12 }; 13 void myInit(void) 14 { 15 glClearColor(0.0, 0.0, 0.0, 0.0); 16 glColor3f(1.0, 0.0, 0.0); 17 glPointSize(2.0); 18 glMatrixMode(GL_PROJECTION); 19 glLoadIdentity(); 20 gluOrtho2D(0.0, 600.0, 0.0, 600.0); 21 } 22 void drawDot(GLint x, GLint y) { 23 glBegin(GL_POINTS); 24 glVertex2i(x, y); 25 glEnd(); 26 } 27 void myDisplay() { 28 glClear(GL_COLOR_BUFFER_BIT); 29 GLintPoint T[3] = { GLintPoint(10, 10), GLintPoint(600, 10), GLintPoint(300, 600) }; 30 int index = rand() % 3; 31 GLintPoint point = T[index]; 32 drawDot(point.x, point.y); 33 for (int i = 0; i < 5000; i++) { 34 index = rand() % 3; 35 point.x = (point.x + T[index].x) / 2; 36 point.y = (point.y + T[index].y) / 2; 37 drawDot(point.x, point.y); 38 } 39 glFlush(); 40 } 41 int main(int argc, char *argv[]) 42 { 43 glutInit(&argc, argv); 44 glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE); 45 glutInitWindowPosition(100, 100); 46 glutInitWindowSize(500, 400); 47 glutCreateWindow("Sierphiski gasket"); 48 glutDisplayFunc(&myDisplay); 49 myInit(); 50 glutMainLoop(); 51 return 0; 52 }
方法2：递归
1 #include <GL/glut.h> 2 #include<stdlib.h> 3 /* initial triangle */ 4 GLfloat v[3][2] = { {10.0, 10.0}, {600.0, 10.0}, {300.0, 600.0} }; 5 int n; 6 void triangle(GLfloat *a, GLfloat *b, GLfloat *c) 7 /* display one triangle */ 8 { 9 glVertex2fv(a); 10 glVertex2fv(b); 11 glVertex2fv(c); 12 } 13 void divide_triangle(GLfloat *a, GLfloat *b, GLfloat *c, int m) 14 { 15 /* triangle subdivision using vertex numbers */ 16 GLfloat v0[2], v1[2], v2[2]; 17 int j; 18 if (m > 0) 19 { 20 for (j = 0; j < 2; j++) v0[j] = (a[j] + b[j]) / 2; 21 for (j = 0; j < 2; j++) v1[j] = (a[j] + c[j]) / 2; 22 for (j = 0; j < 2; j++) v2[j] = (b[j] + c[j]) / 2; 23 divide_triangle(a, v0, v1, m - 1); 24 divide_triangle(c, v1, v2, m - 1); 25 divide_triangle(b, v2, v0, m - 1); 26 } 27 else triangle(a, b, c); /* draw triangle at end of recursion */ 28 } 29 void display(void) 30 { 31 glClear(GL_COLOR_BUFFER_BIT); 32 glBegin(GL_TRIANGLES); 33 divide_triangle(v[0], v[1], v[2], n); 34 glEnd(); 35 glFlush(); 36 } 37 void myinit() 38 { 39 glMatrixMode(GL_PROJECTION); 40 glLoadIdentity(); 41 gluOrtho2D(0.0, 600.0, 0.0, 600.0); 42 glMatrixMode(GL_MODELVIEW); 43 glClearColor(0.0, 0.0, 0.0, 0.0); 44 glColor3f(1.0, 0.0, 0.0); 45 } 46 void main(int argc, char **argv) 47 { 48 n = 15; 49 glutInit(&argc, argv); 50 glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); 51 glutInitWindowSize(500, 400); 52 glutCreateWindow("Sierpinski Gasket"); 53 glutDisplayFunc(display); 54 myinit(); 55 glutMainLoop(); 56 57 }
