Funny you should say that, I was going to say earlier today that I think I'll just sit back and wait for the first people to start asking how to get rid of the fish eye. :-)
Since I remember how frustrating that problem was, I offer this hint to those who might try to implement one of these:
The back of your eye is curved. To remove the fish eye effect, you must adjust the distance you calculate for each wall by taking this curvature into account. In other words you'll need to incorporate some sort of multiplication of the distance by sin or cos to cancel out the curvature that you would see if your retina were flat like the sensor of a camera.
Since I remember how frustrating that problem was, I offer this hint to those who might try to implement one of these:
The back of your eye is curved. To remove the fish eye effect, you must adjust the distance you calculate for each wall by taking this curvature into account. In other words you'll need to incorporate some sort of multiplication of the distance by sin or cos to cancel out the curvature that you would see if your retina were flat like the sensor of a camera.