[Octave-bug-tracker] [bug #64658] delaunay / delaunayn - sometimes return empty if inputs are of type int

[Nicholas Jankowski]

URL:
  <https://savannah.gnu.org/bugs/?64658>

                 Summary: delaunay / delaunayn - sometimes return empty if
inputs are of type int
                   Group: GNU Octave
               Submitter: nrjank
               Submitted: Tue 12 Sep 2023 12:26:28 PM EDT
                Category: Octave Function
                Severity: 2 - Minor
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Nicholas Jankowski
        Originator Email: 
             Open/Closed: Open
                 Release: 8.3.0
         Discussion Lock: Any
        Operating System: Microsoft Windows
           Fixed Release: None
         Planned Release: None


    _______________________________________________________

Follow-up Comments:


-------------------------------------------------------
Date: Tue 12 Sep 2023 12:26:28 PM EDT By: Nicholas Jankowski <nrjank>
for some inputs, delaunayn is fine if the points are specified as doubles or
ints:

for one simplex:

>> pts  =  [0 0 0; 0 10 0; 10 0 0; 0 0 10]
>> delaunayn(pts)
ans =

   1   3   2   4
>> delaunayn(int32(pts))
ans =

   1   3   2   4


or multiple:


>> pts  =  [0 0 0; 0 10 0; 10 0 0; 0 0 10; 5 5 5]
>> delaunayn(pts)
ans =

   5   2   3   1
   5   3   4   1
   5   4   2   1
>> delaunayn(int32(pts))
ans =

   5   2   3   1
   5   3   4   1
   5   4   2   1


but at some point, the type seems to make a difference:


>> pts = [0 0 0; 0 0 10; 0 10 0; 0 10 10; 10 0 0; 10 0 10; 10 10 0; 10 10 10;
5 5 5];

>> delaunayn(pts)
ans =

   7   5   9   1
   7   9   3   1
   6   9   5   1
   6   2   9   1
   6   9   7   5
   6   8   7   9
   4   3   9   1
   4   9   2   1
   4   7   9   3
   4   7   8   9
   4   9   6   2
   4   8   6   9

>> delaunayn(int32(pts))
ans = [](0x4)



stepping through delaunayn for the case above, both come out of the
___delaunayn___ simplex calculation the same.  it seems having the pts as ints
going into the volume check creates erroneous evaluations of the simplex
volume, and it removes them all as 'trivial' simplexes.  recasting pts as
double should be the easiest fix.








    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?64658>

_______________________________________________
Message sent via Savannah
https://savannah.gnu.org/