[Octave-bug-tracker] [bug #53397] Delaunay returns inconsistent (cw/ccw) orientations in 2-D (needs overhaul)

[A.R. Burgers]

Follow-up Comment #5, bug #53397 (project octave):

The proposed m-code solution in the [comment #0 original submission] is still
valid, and is fully vectorized, so no urgent need to go to c++? We are
calculating the cross product already anyway. (wasn't the case at the time
when this bug was submitted)

Could be as simple as this (untested)


diff -r 753e48aa488c scripts/geometry/delaunayn.m
--- a/scripts/geometry/delaunayn.m      Sat Feb 19 13:14:44 2022 -0500
+++ b/scripts/geometry/delaunayn.m      Sat Feb 19 22:41:37 2022 +0100
@@ -110,6 +110,8 @@
     det = cross (p12, p23, 2);
     idx = abs (det (:,3) ./ sqrt (sumsq (p12, 2))) < tol & ...
           abs (det (:,3) ./ sqrt (sumsq (p23, 2))) < tol;
+    is_clockwise = det(:,3) > 0;
+    T(is_clockwise,2:3) =  T(is_clockwise,[3,2]);
   else
     ## FIXME: Vectorize this for loop or convert delaunayn to .oct function
     idx = [];



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