How do I get a line's Angle?

There are a couple of different measurements for working with angles, depending on which angle you are looking for. The angle measurement returns the counter-clockwise angle between two linear objects in the range [0, 360]. The principal_value measurement can be used to normalize this angle to the range [-180, 180]. There is also axis_angle, which treats two linear objects as directionless axes and returns the smallest angle between them, which is going to be in the range [0, 90].

I was not familiar with this "normalized" segment angle displayed in the Show Element window, but it seems to be the counter-clockwise angle within the quadrant from x or y coordinate axis to the segment. This angle will be the same regardless of segment direction, it will just shift the quadrant. If we have the angle from a unit vector [1, 0] to the segment, the normalized angle na can be expressed as a mod 90, or the reminder after dividing a with 90. Like in many programming languages, mod only works on integer numbers in Ravel, so we will have to express this a bit more convoluted as na = a - 90(floor(a/90)).

Suppose that you have a relation mysegment with the segments that you want to check. You could then find this angle by:

(define mysegment_angle
  (transform (s) mysegment
    (s (angle (CREATE_VECTOR 1 0) s))))

(define mysgement_normalized
  (transform (s a) mysegment_angle
    (s a - 90.0*(floor a/90.0))))

You would then subtract this from your constraint value and compare the absolute value with some epsilon.

There are a couple of different measurements for working with angles, depending on which angle you are looking for. The angle measurement returns the counter-clockwise angle between two linear objects in the range [0, 360]. The principal_value measurement can be used to normalize this angle to the range [-180, 180]. There is also axis_angle, which treats two linear objects as directionless axes and returns the smallest angle between them, which is going to be in the range [0, 90].

I was not familiar with this "normalized" segment angle displayed in the Show Element window, but it seems to be the counter-clockwise angle within the quadrant from x or y coordinate axis to the segment. This angle will be the same regardless of segment direction, it will just shift the quadrant. If we have the angle from a unit vector [1, 0] to the segment, the normalized angle na can be expressed as a mod 90, or the reminder after dividing a with 90. Like in many programming languages, mod only works on integer numbers in Ravel, so we will have to express this a bit more convoluted as na = a - 90(floor(a/90)).

Suppose that you have a relation mysegment with the segments that you want to check. You could then find this angle by:

(define mysegment_angle
  (transform (s) mysegment
    (s (angle (CREATE_VECTOR 1 0) s))))

(define mysgement_normalized
  (transform (s a) mysegment_angle
    (s a - 90.0*(floor a/90.0))))

You would then subtract this from your constraint value and compare the absolute value with some epsilon.