   gluPerspective 1st parameter
  Does anybody get the 1st parameter, fovy, for gluPerspective?  I think I get the other three.I have an old Red Book right here and there's a diagram with a camera and stuff.  It says it's the angle of the field of view in the yz-plane and it has to be between 0 and 180.I don't understand that at all.   
  I'm still trying to rotate a camera in a world since I'm also trying to learn through the redbook, but I managed to set perspective already, so:You define a "near" and a "far", right? Imagine the "near" is a square, where the bottom of the square is for example at y = 0; Imagine the camera is also at y= 0. Now imagine the "near" is at z = 10, while the camera is at z = 0; If you wanted to make the top of the "near" square be y = 10, the angle would be 45 degrees. Then imagine "far" was at z = 20. In that case, the top "far" would be y = 20 (since the angle is 45).Oh, and also, the reason why you only define the top and bottom sides of the "near" square (with the angle), is because the ratio pretty much defines the sides of that same square.It's not easy to explain with words. Just try to understand this example and look at the diagram and you should understand it.   ;  Oh, okay.  So if the camera is a point on the z-axis and you drew a line straight out from the camera, parallel to the zx plane all the way to the left side center of the near rectangle, the angle between that line and the z-axis would be fovy.  Right?  Oh, wait, no, it would be fovy/2.I don't get why 180 is the MAX value.  Wouldn't that make the view infinity?   ;  Yes, it would be fovy/2 as the angle to the top of the square is fovy.   ;  In 2D, you can imagine it (ignoring the near and far plane for a second) as a sector of a circle surrounding your camera. If it's 180 degrees, it's basically half-circle, 360 degrees would mean the whole circle, which would produce panorama picture of all your surroundings