[GRASS-user] voxel from dems

[Soeren Gebbert]

Dear Maciej,

On Tuesday 25 July 2006 21:47, Maciej Tomaszczyk wrote:
> hello all
> 
> i try to make a grid3d geological model from a drillhole data
> first i generated a couple of dems which represent a geological bounduary,
> (using Z values of geological bounduary from drillholes), 
> after that i used r3.out.vtk and everythink looked ok in paraview, but 
> i got a big problem with some geological structures wich are not more less planar
> as salt diapir or overturned folds, its mean that in some drillhole profills more 
> than one Z value exist (which represent the same bounduary)  
> and i am not able to make a DEM using both Z values.

There is no way to create such volume surfaces with r3.out.vtk + dems,
because of the limits of dems to have only one Z value per cell.

But there are maybe some other ways:

One way would be to modell the geological structures as 3d faces in
grass and export this with v.out.vtk. But this is very .... hard.

The second way would be to modell the geological structures as raster
map slices at a specific hight and put them together with r.to.rast3. 
take a look at:
http://www-pool.math.tu-berlin.de/~soeren/grass/modules/screenshots/r.to.rast3.png

Now you can export this data with r3.out.vtk and use the threshold or isosurface 
filter of Paraview to extract the geological structure. To use these Filter you will need
VTK point data (export with r3.otu.vtk or the Cell-Data-To-Point-Data filter of Paraview).

For now there is no way to import the generated VTK isosufaces into grass. 
And it would be nice if GRASS would have such a threshold or isosurface modules like VTK. 
But this is just a wish... . 
Well .... i have some ideas in my mind how to implement this. ;)

Best regards
Soeren

> maybe some of you got the same problem
> can you help me solve it
> best
> maciej  
> 
> Maciej Tomaszczyk
> Polish Geological Institute
> Geological Mapping Department
> 
>