Question

For some reason when I resize my OpenGL windows, everything falls apart. The image is distorted, the coordinates don’t work, and everything simply falls apart. I am sing Glut to set it up.

//Code to setup glut glutInitWindowSize(appWidth, appHeight); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA); glutCreateWindow('Test Window');  //In drawing function glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glClear(GL_COLOR_BUFFER_BIT);  //Resize function void resize(int w, int h) {     glMatrixMode(GL_PROJECTION);     glLoadIdentity();     gluOrtho2D(0, w, h, 0); } 

The OpenGL application is strictly 2D.

This is how it looks like initially: http://www.picgarage.net/images/Corre_53880_651.jpeg

this is how it looks like after resizing: http://www.picgarage.net/images/wrong_53885_268.jpeg

Answer 1

You should not forget to hook the GLUT ‘reshape’ event:

glutReshapeFunc(resize); 

And reset your viewport:

void resize(int w, int h) {     glViewport(0, 0, width, height); //NEW     glMatrixMode(GL_PROJECTION);     glLoadIdentity();     gluOrtho2D(0, w, h, 0); } 

A perspective projection would have to take the new aspect ratio into account:

void resizeWindow(int width, int height) {     double asratio;      if (height == 0) height = 1; //to avoid divide-by-zero      asratio = width / (double) height;      glViewport(0, 0, width, height); //adjust GL viewport      glMatrixMode(GL_PROJECTION);     glLoadIdentity();     gluPerspective(FOV, asratio, ZMIN, ZMAX); //adjust perspective     glMatrixMode(GL_MODELVIEW); }