Start and stop GLUT animation - c

Question

I'm working on a project in c, where I'm going to make some heavy physics calculations, and I want the ability to see the results when I'm finished. The way it works now is that I run GLUT on the main thread, and use a seperate thread (pthread) to do input (from terminal) and calculations. I currently use glutTimerFunc to do the animation, but the problem is that that function will fire every given time intervall no matter what. I can stop the animation by using an if statement in the animation function, stopping the variables from being updatet, but this uses a lot of unnecessary resources (I think).
To fix this problem I was thinking that I could use an extra thread with a custom timer function that I could controll myself (without glutMainLoop messing things up). Currently this is my test function to check if this would work (meaning that the function itself is in no way finished). It runs in a seperate thread createt just before glutMainLoop:
void *threadAnimation() {
while (1) {
if (animationRun) {
rotate = rotate+0.00001;
if (rotate>360) {
rotate = rotate-360;
}
glutSetWindow(window);
glutPostRedisplay();
}
}
}
The specific problem I have is that the animation just runs for a couple of seconds, and then stops. Does anybody know how I can fix this? I am planning to use timers and so on later, but what I'm looking for is a way to ensure that glutPostRedisplay will be sent the right place. I tought glutSetWindow(window) was the solution, but apparently not. If I remove glutSetWindow(window) the animation still works, just not for as long, but runs much faster (so maybe glutSetWindow(window) takes a lot of resources?)
btw the variable "window" is created like this:
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(854, 540);
glutInitWindowPosition(100, 100);
window = glutCreateWindow("Animation View");
init();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
timerInt = pthread_create(&timerThread, NULL, &threadAnimation, NULL);
glutMainLoop();
I don't acctually know if this is correct, but it compiles just fine. Any help is greatly appriciated!

Answer 1

Here's a little idea, create class that will contain all dynamic settings:
class DynamicInfo {
public int vertexCount;
public float *vertexes;
...
DynamicInfo &operator=( const DynamicInfo &origin);
};
And than main application will contain those:
DynamicInfo buffers[2];
int activeBuffer = 0;
In animation thread just draw (maybe use some threads locks for one variable):
DynamicInfo *current = buffers + activeBuffer; // Or rather use reference
In calculations:
// Store currently used buffer as current (for future manipulation)
DynamicInfo *current = buffers + activeBuffer;
// We finished calculations on activeBuffer[1] so we may propagate it to application
activeBuffer = (activeBuffer + 1)%2;
// Let actual data propagate to current buffer
(*current) = buffers[activeBuffer];
Again it's locking one variable.