diff options
Diffstat (limited to 'flower/offset.cc')
| -rw-r--r-- | flower/offset.cc | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/flower/offset.cc b/flower/offset.cc index b7f5df4026..cdb63f3f86 100644 --- a/flower/offset.cc +++ b/flower/offset.cc @@ -182,3 +182,39 @@ Offset::swapped () const { return Offset (coordinate_a_[Y_AXIS], coordinate_a_[X_AXIS]); } + +Offset +offset_directed (Real angle) +{ + if (angle <= -360.0 || angle >= 360.0) + angle = fmod (angle, 360.0); + // Now |angle| < 360.0, and the absolute size is not larger than + // before, so we haven't lost precision. + if (angle <= -180.0) + angle += 360.0; + else if (angle > 180.0) + angle -= 360.0; + // Now -180.0 < angle <= 180.0 and we still haven't lost precision. + // We don't work with angles greater than 45 degrees absolute in + // order to minimize how rounding errors of M_PI/180 affect the + // result. That way, at least angles that are a multiple of 90 + // degree deliver the expected results. + // + // Sign of the sine is chosen to avoid -0.0 in results. This + // version delivers exactly equal magnitude on x/y for odd multiples + // of 45 degrees at the cost of losing some less obvious invariants. + + if (angle > 0) + if (angle > 90) + return Offset (sin ((90 - angle) * M_PI/180.0), + sin ((180 - angle) * M_PI/180.0)); + else + return Offset (sin ((90 - angle) * M_PI/180.0), + sin (angle * M_PI/180.0)); + else if (angle < -90) + return Offset (sin ((90 + angle) * M_PI/180.0), + sin ((-180 - angle) * M_PI/180.0)); + else + return Offset (sin ((90 + angle) * M_PI/180.0), + sin (angle * M_PI/180.0)); +} |