[GRASS-dev] CELL/FCELL/DCELL [was: Re: r.mapcal rand() strangeness]

[Helena Mitasova]

On Mar 1, 2008, at 5:18 PM, Maciej Sieczka wrote:

> Glynn Clements pisze:
>> Maciej Sieczka wrote:
>
>>> I was going to add this information, but I'm not sure if I  
>>> understand correctly that GRID3D is always floating point. Raster  
>>> intro seems to suggest so, but r3.mapcalc suggests the opposite,  
>>> eg.: "Note: If you calculate with integer numbers, the resulting  
>>> map will be integer". Please tell me.
>
>> I suspect that's probably an artifact of verbatim copying from the
>> r.mapcalc documentation.
>> I'm fairly sure that G3D only supports FP.
>
> Can you confirm if double precision only? I guess so by experiments  
> with r3.mapcalc - eg.:
>
> $ r3.mapcalc 'map=float(1)'
> $ r3.info map -t
> datatype="double"
>
>> Looking at the r3.mapcalc code, the only way that you can get CELL
> > values from a 3D grid is if you use the various # operators to  
> perform
> > colour lookups.
>
> It still yields double for me:
>
> $ r3.mapcalc 'map_g=g#map'
> $ r3.info map_g -t
> datatype="double"
>
> ?
>
>
>
> Can anybody please say what is the official name for GRASS 3d  
> raster data, which should be used in the raster intro? So far I  
> have found the following:
>
> $ cd /usr/local/grass-6.3.svn/docs/html$
>
> $ grep -r -i "3d raster" . | wc -l
> 89
> $ grep -r -i voxel . | wc -l
> 50
> $grep -r -i g3d . | wc -l
> 46
> $ grep -r -i GRID3D . | wc -l
> 17
> $ grep -r -i "3d cell" . | wc -l
> 6
>
> "3d cell" (which r3.info uses in it's output too BTW) seems kindoff  
> strange - 3d rasters are supposed to be only FP data type, whereas  
> in 2D raster GRASS lingo "CELL" designates the integer data type.

we have used "3D raster is called GRID3D" (similarly as 2D integer  
raster is called CELL) in the GRASSbook,
but we have used voxel in few places too (I am not sure whether that  
was good).
g3d is historical and 3d cell sounds confusing - it could get
mixed up with CELL.

Helena


>
> Maciek