gluPerspective

One of the convenience methods removed from OpenGL ES is gluPerspective. At some point, I ran across the code for this method (this isn't my code, but I'm not sure who I got it from. If this came from you, let me know and I will credit you). Anyone who's feeling sad because gluPerspective is not available on the iPhone, rejoice, for here it is:

- (void)gluPerspective:(double)fovy :(double)aspect :(double)zNear :(double)zFar
{
 // Start in projection mode.
 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
 double xmin, xmax, ymin, ymax;
 ymax = zNear * tan(fovy * M_PI / 360.0);
 ymin = -ymax;
 xmin = ymin * aspect;
 xmax = ymax * aspect;
 glFrustumf(xmin, xmax, ymin, ymax, zNear, zFar);
}

Seems silly to not have this, given how short it is.