[GRASS-user] Fwd: 3-D plane workflow

[Anna Kratochvílová]

On Wed, Feb 27, 2013 at 12:38 AM, Adam Dershowitz
<adershowitz at exponent.com> wrote:
> I would like to be able to put some surfaces in the space over a DEM.  In
> other words, I have a DEM, and then I need to calculate some regions that
> are "keep-out zones" in space above.  I can calculate where these surfaces
> are fairly easily in Python, for example.  So the output of my calculation
> would be some points.  In the easiest example, it would just be 4 sets of
> x,y,z that represent the four corners of a plane.
> I would then like to be able to visually show this plane (or multiple
> planes), over the DEM, and show that the DEM does, or doesn't, penetrate
> this surface.  If it does penetrate, I would like to be able to calculate
> the penetration height.
>
> The kind of thing that I would like to do, would end up looking like the
> examples of Slovakia precipitation that Mitasova has done.  Some of those
> examples show a DEM, and then a surface that is being penetrated by the DEM.
> I have been reading some of the examples for 3D visualization (such as here:
> http://grasswiki.osgeo.org/wiki/Help_with_3D), but figured that a post here,
> but might get me a little more guidance about a general suggested workflow.
>
> In those examples, are the isosurfaces does as 3D rasters?  If I just want a
> plane in space, and I have the four corner points, is a 3D raster seem like
> the best way to draw it?  Are those examples displayed with NVIZ or
> paraview?
>
> Is the following a reasonable approach:
>
> Calculate the surfaces in some code and export as faces:
>
> F 4
>  0 100 10
>  50 50 80
>  0 0 10
>  0 100 10
>
> Then, import into Grass with v.in.ascii.
> Next, I would have to convert to a raster:  v.to.rast.
> Then, I would have to convert to an elevation:  r.to.rast3elev
> Finally, I could export both the surfaces and the ground DEM with
> r3.out.vtk, and visualize with paraview.
>
> Is this a reasonable workflow?  If I just need a semitransparent surface, is
> it necessary for it to be 3D, or can it be done with 2.5D (all I really need
> is x,y and elevation, like a DEM).  For, example, I might be able to just
> skip the raster version and use v.out.vtk?    Or maybe I can just use nviz
> to visualize what I need, if I can get it to the right format.
> If I do convert the plane to a raster, I suppose I can then use mapcalc to
> calculate the height difference between the plane and the ground DEM?
>
> I am just looking for some general workflow guidance for a good overall
> approach to get going.  It seems like there are some things that are not as
> clear about 3D work in GRASS, and I am just trying to get a reasonable
> picture.
> Any thoughts are greatly appreciate.
>
> Thanks much,
>


Hi Adam,

(sorry if you already got this email)

I am not sure if this is exactly what you want but have a look at the
attached screenshots. This is done in wxNviz. I created a plane (3
points) with

v.in.ascii -n input=inputFile.txt output=out format=standard separator=" "  z=3

The file containes what you already used (F 4 ...). Then you can
display it in 3D view. However, the transparency of the surface is not
working well together with the vector. You can play with using wire
style as in the
screenshot. If it is not clear, just ask for more details.

Regards,
Anna
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