[GRASSLIST:10514] Dxf and other 3d objects in NVIZ

GRASS GRASS user
1

Hi All,

I’m new to the list but not Grass which i use primarily on Mac OS X. Is there an alternative option to getting 3d objects into NVIZ. I have tried to obtain the v.in.dxf (OpenDWG Toolkit) but have failed.

Has anyone had success with buildings or Windturbines in thier correct geographic positions. I have a ‘.dxf’ instances i would like to import.

Thanks,

Paul Shapley

2

Hi list,

I've got some problems with r.topidx.

I've used both normal elevation maps and preprocessed (with r.fill.dir) depressionless elevation maps, but the resulting topidx map is full of artifacts

- a lot of -10 values in the resulting topidx map
- with some elevation maps, a kind of gridlike raster pattern is produced, with a background of NULL values and a grid consisting of both -10 and positive values.

Any ideas?

cheers
wouter

3

Hi,

Since r.topidx tries to calculate topidx values based on the resolution of a
dem, the dem has to have the right resolution. If the resolution is less than
the actual grid size, r.topidx cannot know whether cells within a grid are
sinks or not.

When your elevation data is (assume its resolution is 1):

123
456
789

If the above data has a resolution greater than 1 (let's say 3 here), the
imported raster will look like the following:

111222333
111222333
111222333
444555666
444555666
444555666
777888999
777888999
777888999

Now, GRASS cannot say those duplicated (because of greater resolution) 9 cells
per each grid are really one grid or 9 grids. Similarly, r.topidx treats those values as sinks.

To find the correct resolution of your dem data, run the following script
(find_res.sh my_dem):
---
#!/bin/sh
r.stats -1n "$1" | awk '{
  v = $0
  if(NR > 1 && v != v0){
    if(min_n == 0 || n < min_n)
      min_n = n
    n = 1
    v0 = v
    next
  }
  v0 = v
  n++
}
END{
  print min_n
}'
---

The above script counts the minimum number of duplicated cell values. Now you
want to multiply the current resolution by the printed number.

g.region -p | grep nsres | awk '{print $2}'

  1

find_res.sh my_dem

  3

g.region res=3 # 1 * 3
d.erase
r.topidx in=my_dem ou=topidx

Huidae Cho

On Wed, Feb 22, 2006 at 11:39:36AM +0000, Wouter Buytaert wrote:

Hi list,

I've got some problems with r.topidx.

I've used both normal elevation maps and preprocessed (with r.fill.dir)
depressionless elevation maps, but the resulting topidx map is full of
artifacts

- a lot of -10 values in the resulting topidx map
- with some elevation maps, a kind of gridlike raster pattern is produced, with
a background of NULL values and a grid consisting of both -10 and positive
values.

Any ideas?

cheers
wouter

4

You can use v.extrude for buildings. I tried it and it is pretty slick.

Michael

Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
Arizona State University
Tempe, AZ 85287-2402

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

From: Paul Shapley p.shapley@gmail.com
Date: Wed, 22 Feb 2006 11:04:53 +0000
To: GRASSLIST@baylor.edu
Subject: [GRASSLIST:10514] Dxf and other 3d objects in NVIZ

Hi All,

I’m new to the list but not Grass which i use primarily on Mac OS X. Is there an alternative option to getting 3d objects into NVIZ. I have tried to obtain the v.in.dxf (OpenDWG Toolkit) but have failed.

Has anyone had success with buildings or Windturbines in thier correct geographic positions. I have a ‘.dxf’ instances i would like to import.

Thanks,

Paul Shapley

5

I also tried for some time to get 3d shapes from a CAD file into GRASS as 3d vectors. I used lots of different methods - extruded shapes (like v.extrude but in CAD), individual faces/surfaces, etc., and never had anything come out right in GRASS. I was using v.in.ogr to import Microstation .dgn files - which works fine for 2d vectors, and for 2 1/2d vectors – contour lines with elevation – but not for proper 3d objects.

Nick Cahill

On Feb 23, 2006, at 8:19 AM, Michael Barton wrote:

You can use v.extrude for buildings. I tried it and it is pretty slick.

Michael

Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
Arizona State University
Tempe, AZ 85287-2402

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

From: Paul Shapley <p.shapley@gmail.com>
Date: Wed, 22 Feb 2006 11:04:53 +0000
To: <GRASSLIST@baylor.edu>
Subject: [GRASSLIST:10514] Dxf and other 3d objects in NVIZ

Hi All,

I’m new to the list but not Grass which i use primarily on Mac OS X. Is there an alternative option to getting 3d objects into NVIZ. I have tried to obtain the v.in.dxf (OpenDWG Toolkit) but have failed.

Has anyone had success with buildings or Windturbines in thier correct geographic positions. I have a ‘.dxf’ instances i would like to import.

Thanks,

Paul Shapley