LinuxCNC G-code assumes that the programmer wanted a full circle if the coordinates of the start and end points in the plane are "the same".
Currently both the preview interpreter and motion use the angle between the start and end points of an arc to decide if the start and end coordinates are “identical” and if so it is assumed that a full turn was wanted. https://github.com/LinuxCNC/linuxcnc/blob/master/src/libnml/posemath/_posemath.c#L1824 https://github.com/LinuxCNC/linuxcnc/blob/master/src/emc/rs274ngc/gcodemodule.cc#L1002 They calculate the angle in different ways and get slightly different results. (ie, if you carefully tweak the code, you can have the preview and actual motion give different results. This probably doesn't matter very often. A problem arises if a _very_ large radius is computed to generate a nearly-straight line. (In the example in issue 1528 one of the problem arcs is 5mm long, but has a 7km radius. The coordinates are very different, but the included angle is very, very small) Given that arcs are programmed in terms of XY coordinates, I think it makes no sense to judge the smallness of an arc by internal angle. I propose doing it purely on the basis of hypotenuse distance in the plane. (Incidentally, part of the reason that the preview and motion differ is because motion is in metric and preview is in imperial! At least with a metric config and metric G-code. I will need to test the 4 combinations) -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
