triangles.cpp

// File triangles.cpp
// Hugo Gallée
// Sat Feb 25 23:06:03 CET 2012

#include <GL/glut.h>
#include <math.h>

typedef struct point {
  float x;
  float y;
} Point;


void drawTriangle (Point a, Point b, Point c) {
  float z = 0.0;
  glBegin(GL_TRIANGLES);
    glColor3f (1.0, 0.0, 0.0);
    glVertex3f(a.x, a.y, z);
    glVertex3f(b.x, b.y, z);
    glVertex3f(c.x, c.y, z);
  glEnd();
}

void init (void) {
    // select clearing color
    glClearColor (1.0, 1.0, 1.0, 0.0);

    // initialize viewing values
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}

void display(void) {
    // clear all pixels
    glClear (GL_COLOR_BUFFER_BIT);

    Point a, b, c;
    float margin = 0.1;
    float size = 0.4;
    a.x = margin;
    a.y = margin;
    b.x = margin + size;
    b.y = margin;
    c.x = margin;
    c.y = margin + size;

    for (int i = 0; i < 6; i++) {
      drawTriangle(a, b, c);
      margin /= 2;
      a.x += margin + size;
      size /= 2;
      b.x = a.x + size;;
      c.x = a.x;
      c.y = a.y + size;
    }

    // Swap the buffers to show the oneon which we writed
    glutSwapBuffers();
}

/*
 * Declare initial window size, position, and display mode
 * (double buffer and RGB).  Open window with "hello"
 * in its title bar.  Call initialization routines.
 * Register callback function to display graphics.
 * Enter main loop and process events.
 */
int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize (500, 500);
    glutInitWindowPosition (100, 100);
    glutCreateWindow ("triangles");
    init ();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}