Q: What does "Round Values" do?
A: It rounds the final x and y values for each point that is graphed to the nearest integer. It can help minimize anti-aliasing that occurs. It reduces the accuracy of the image, however, so I suggest using it on very large images only.
Q: What units is the observer distance measured in?
A: I call them "standard units," and they underly the projection. The field is ten units wide and deep. All locations must be converted to standard units to be graphed. All internal math is done in standard units. You can see this in various places if you look at the code.
Q: Why does the image get larger/smaller when I change the observer distance?
A: Try checking "Auto Zoom." That should take care of it, although it doesn't work well with all functions. Specifically, if a function goes unbounded within the specified domain, it won't work well.