spur_gear: fix negative helix angles

The helix code previously included an assumption that the angle is positive when calculating the slice count, which caused negative angles to always produce only 1 slice.

This fix adds an abs() call around the twist to produce the same slice count for both directions.
This commit is contained in:
John Doe 2024-12-18 16:36:38 -07:00
parent 0f09d1fac9
commit db8236dbed

View file

@ -1013,7 +1013,7 @@ module spur_gear(
: assert(false,"atype must be one of \"root\", \"tip\" or \"pitch\"");
circum = 2 * PI * pr;
twist = 360*thickness*tan(helical)/circum;
slices = default(slices, ceil(twist/360*segs(pr)+1));
slices = default(slices, ceil(abs(twist)/360*segs(pr)+1));
default_tag("remove", internal) {
attachable(anchor,spin,orient, r=anchor_rad, l=thickness) {
zrot(gear_spin)