[GRASS-user] raster drape color question

[Glynn Clements]

Ken wrote:

> I'm a total grass newbie.  When I drape a map over my base dem map the 
> "draped" map blows away my colors in the dem map.  Even where the drape 
> map doesn't appear to have any values. (the dem map seems to get a sort 
> of grey tone in those areas)  Is there a way to preserve the color map 
> from my base map and have the drape map only overlay the colors where it 
> actually has values?  ie: is there a transparency color i can set?  the 
> "(transparent null value cells)" checkbox doesn't seem to change anything.

In the GUI, if you specify a "drape" map, it uses d.his (rather than
d.rast), with the "base" map used for the intensity (i_map= option)
and the "drape" map used for the hue (h_map=). In that case, the base
map should be grey-scale (typically the aspect map produced by
r.slope.aspect); also, the "transparent null value cells" option
doesn't work with d.his.

If you just want to overlay multiple maps, create a separate layer for
each map, with the "transparent" option enabled for all of the upper
layers.

-- 
Glynn Clements <glynn at gclements.plus.com>