[Octave-bug-tracker] [bug #53187] quiver3 draws z-axis aligned arrows with no visible head (line aligned to stem)

[Nicholas Jankowski]

Update of bug#53187 (group octave):

                 Summary: Will not display arrows for quiver3 in z axis =>
quiver3 draws z-axis aligned arrows with no visible head (line aligned to
stem)

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Follow-up Comment #5:

this still exists in octave 9.0.90

a mwe is to simply plot:

vz = quiver3(0,0,0,0,0,1)

see attached. 

the line properties for the arrow are:


>> get(get(vz, 'children'), 'xdata')
ans =
{
  [1,1] = 0
  [2,1] =

       0     0     0   NaN

  [3,1] =

       0     0   NaN

}

>> get(get(vz, 'children'), 'ydata')
ans =
{
  [1,1] = 0
  [2,1] =

       0     0     0   NaN

  [3,1] =

       0     0   NaN

}

>> get(get(vz, 'children'), 'zdata')
ans =
{
  [1,1] = 0
  [2,1] =

     0.6000   0.9000   0.6000      NaN

  [3,1] =

          0   0.9000      NaN


so the head is child #2, a 3-point line. the x and y values are currently
being calculated such that both head segments lie along the arrow stem. 
Matlab example shown as well. head is clearly calculated wider, to about
+/-0.15 (axes scale make them look rather large)

(file #55706, file #55707)

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Additional Item Attachment:

File name: quiver_nohead.png              Size:27 KB
    <https://file.savannah.gnu.org/file/quiver_nohead.png?file_id=55706>

File name: quiver_nohead_matlab.png       Size:18 KB
   
<https://file.savannah.gnu.org/file/quiver_nohead_matlab.png?file_id=55707>


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