Question

I have a sphere drawn on the screen. When I press a button I want the sphere to slowly move to the right. I am trying to accomplish this with

for (int i = 0;i<10;i++)
{
sphere.moveToRight(0.1);
glutPostRedisplay();
sleep(1000);
}

But instead of animated, it waits a few seconds and then draws the sphere in the final location. I assume it is because sleep is stopping the glutPostRediplay(). Any ideas of how to accomplish this basic annimation?

Answer 1

You are using glutPostRedisplay wrong.

Check out: http://www.opengl.org/resources/libraries/glut/spec3/node20.html

glutPostRedisplay marks the normal plane of current window as needing
to be redisplayed. glutPostWindowRedisplay works the specified window
as needing to be redisplayed. After either call, the next iteration
through glutMainLoop, the window’s display callback will be called to
redisplay the window’s normal plane. Multiple calls to
glutPostRedisplay before the next display callback opportunity
generates only a single redisplay callback. glutPostRedisplay may be
called within a window’s display or overlay display callback to
re-mark that window for redisplay.

Which means, after 10 seconds your image will get refreshed once.