Arc Compensation

A few weeks ago Nophead pointed out that when the RepRap extruder moves round an arc it deposits too much material on the inside of a curve and not enough on the outside, owing to the differential in speeds caused by the slightly different radii. This is insignificant for large radii, but quite important for small ones.

I did the sums (see this link) and then put the compensation factor in the Java code, which is now checked into the repository. If you want to see how the code works, look at the org.reprap.geometry.polygons.RrPolygon class and see the function arcCompensate; the link gives the algebra, so I should start with that before looking at the code.

There are a couple of new parameters to control the behaviour (the default is not to do the compensation). The web page explains them too.