[Octave-bug-tracker] [bug #55384] Adding a light removes the transparency from surfaces with 'FaceColor'

[Francisco Vazquez]

URL:
  <https://savannah.gnu.org/bugs/?55384>

                 Summary: Adding a light removes the transparency from
surfaces with 'FaceColor'
                 Project: GNU Octave
            Submitted by: v44r
            Submitted on: Fri 04 Jan 2019 12:11:22 PM UTC
                Category: Plotting with OpenGL
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.4.1
        Operating System: GNU/Linux

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Details:


[x,y,z] = sphere;
surf(x, y, z, 'FaceColor', 'red', 'FaceAlpha', 0.2);


A transparent, red sphere is drawn. However, after adding a light:


light;


The sphere becomes opaque. This happens in fltk and qt.

Note that if the sphere is drawn without 'FaceColor'


[x,y,z] = sphere;
surf(x, y, z,'FaceAlpha', 0.2);
light;


the transparency is kept after adding a light.

In Matlab both cases produce a transparent sphere.




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