[GRASS-dev] [GRASS GIS] #2175: m.nviz.image: adding transparency_value= changes raster layer stacking order

[GRASS GIS]

#2175: m.nviz.image: adding transparency_value= changes raster layer stacking
order
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 Reporter:  hamish                      |       Owner:  grass-dev@…              
     Type:  defect                      |      Status:  new                      
 Priority:  normal                      |   Milestone:  6.4.4                    
Component:  Default                     |     Version:  svn-trunk                
 Keywords:  m.nviz.image, transparency  |    Platform:  Linux                    
      Cpu:  x86-64                      |  
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Comment(by annakrat):

 Replying to [comment:5 hamish]:
 > Some progress, and a workaround:
 >
 > The question then becomes do we try and come up with a better sorting
 strategy or render in the order the layers were added, and why does it
 work correctly when transparency_value= is left unset even though the
 layers are sorted with the DEM rendering last? Is there a second bug which
 was masking the first?
 >

 It works in wxNVIZ, too, with some limitations. It depends on the layer
 order (as you are explaining) so if you set transparency for the last
 loaded layer, it works, otherwise you get weird results. It's better than
 before (we can achieve what we need) but it's even more confusing for
 users (now it would be working only sometimes instead of not at all).
 Could we have the  transparent layers as the last ones? Perhaps using
 `GS_get_att` we can identify them?

 The transparency_value=0 causes setting the transparency attribute. We can
 probably just add another condition (to test specifically 0) to
 m.nviz.image/surface.c (line 145).

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2175#comment:6>
GRASS GIS <http://grass.osgeo.org>