#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):
Some progress, and a workaround:
sort_surfs_max() in lib/nviz/draw.c seems working as expected and to
return the same result both with and without the transparency_value=
option.
and yet, bypassing the sort with the following patch seems to fix(bypass)
the problem:
{{{
Index: lib/nviz/draw.c
===================================================================
--- lib/nviz/draw.c (revision 58790)
+++ lib/nviz/draw.c (working copy)
@@ -107,7 +107,8 @@
}
maxvals[indices[i]] = max + 1;
- id_sort[i] = surf[indices[i]];
+// id_sort[i] = surf[indices[i]];
+ id_sort[i] = surf[i];
}
return 1;
}}}
The sort returns layers ordered lowest to highest maximum value, and thus
for a planar surface cutting through a DEM the DEM will always be higher,
so the constant surface will always be rendered first, since it has a
lower maximum (& so will be sorted to first in the list of surfaces to
render).
proof:
by changing the constant surface from elevation_value=100 to 160
(slightly more than the max of NC's elevation map), it renders correctly.
By lowering it slightly to 150 (just below elevation's max) the semi-
transparent constant surface gets overwritten by the DEM.
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?
cheers,
Hamish
--
Ticket URL: <https://trac.osgeo.org/grass/ticket/2175#comment:5>
GRASS GIS <http://grass.osgeo.org>
_______________________________________________
grass-dev mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/grass-dev
