[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
----------------------------------------+-----------------------------------
 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                      |  
----------------------------------------+-----------------------------------

Comment(by hamish):

 Replying to [comment:6 annakrat]:
 > Could we have the  transparent layers as the last ones? Perhaps
 > using `GS_get_att` we can identify them?

 Hi,

 it's not specifically transparent surfaces, or even constant surfaces that
 cut through.

 for example instead of null areas (which leave jagged triangles at their
 edge) to mask off below sea level areas you can have a constant opaque
 white surface at 0.0 to do the same, while the real DEM surface plunges
 below. with that trick you get a nice crisp edge at the water's edge.

 you might also want a dynamic surface which breaks but does not exceed the
 max elevation of the main DEM, transparent or not. (e.g. a raster building
 [are semi-transparent 3D vector surfaces possible?])

 I guess the question is if allowing a user definable layer order is the
 way around all this?


 I'm also having trouble with sub-integer constant elevation values, even
 after changing TYPE_INTEGER to TYPE_DOUBLE in m.nviz.image/args.c for
 those options which are later parsed with atof(), so theoretically should
 accept floating point values. e.g. 11.0-11.4 see reasonable but 11.5 and
 11.7 drop down to near 11.0 again. it's all a bit weird but probably a
 matter for another ticket.


 Hamish

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/2175#comment:7>
GRASS GIS <http://grass.osgeo.org>