Arcs and circles milling with bCNC
No matter the software or the post processor you use when you do an autoleveling (heightmap) process in bCNC, the software will modify your g-code. This is not a problem for lines but for arcs and circles it will decompose your curves into small segments so it can interpolate and adapt the height of the cutter to your surface. Even if this can be ok for small circles, it may change the shape of your piece in an undesired way. If you don't want this you have to find another way of levelling your material or omit the autoleveling. In that way it will send the arc g-code as arcs and you will have a smooth curve.