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Alternative to "Connect" scatter data point? (Read 4278 times)
easylin
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Alternative to "Connect" scatter data point?
12/04/07 at 03:27:59
 
hi
 
my data set is fully scattered points.
# (3-Vector and 1 scalar)
# X Y Z Value
 
I would like to find out a surface which can be represented by those scattered points.
In openDX I knew only "Connect" Module.
(I have also tried in other vis tools, like ParaView or gnuplot)
I think all of them may perform just Delaunay triangulation algorithm(or mesh generating, surface fitting, non-grid to gird data mapping...etc)
 
But the result of them is not alway *good*.
 undecided is there any other alternative or any way to do such task or to "tune" the result ?
 
especially some data set has "critical point"(e.g. extreme Z value).
The "Connect" would go wrong.
 undecided how can I overcome this problem?
 
thanks
 
 
 
 
 
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dmoroian
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Re: Alternative to "Connect" scatter data point?
Reply #1 - 12/04/07 at 04:00:45
 
I've just red the documentation for Connect. It seems that it creates only triangles (2d cells) while you have a 3d field. It is still a good solution, but I think that AutoGrid would be a much better option for you.
 
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TheBard
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Re: Alternative to "Connect" scatter data point?
Reply #2 - 02/01/08 at 07:25:06
 
This was posted some time ago, but I attempt a reply anyway.
 
There are many ways to grid scattered data, e.g. make a continuous line, surface or volume from scattered input. OpenDX is a visualisation tool, not a tool for gridding data. I started out with OpenDX using the internal gridding tools, but the nearest neighbor interpolation in AutoGrid is limited and slow for large data sets. So we grid our data outside OpenDX and use it only for visualisation.  
 
Gridding algorithms can be found in various places on the internet, keywords are "b-spline", "kriging", "weighted distance" and "nearest neighbor" interpolation. A nice tool for making maps from xyz data can be found here http://gmt.soest.hawaii.edu/ The output from "surface" is a netCDF file that can be imported easily in OpenDX using the nc2dx software you can get on the OpenDX home page.
 
Most of the algorithms available are for 2D or 3D data sets for making lines and surfaces, gridding of 4D data is not straightforward...
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easylin
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Re: Alternative to "Connect" scatter data point?
Reply #3 - 02/01/08 at 12:19:20
 
Quote from TheBard on 02/01/08 at 07:25:06:

I started out with OpenDX using the internal gridding tools, but the nearest neighbor interpolation in AutoGrid is limited and slow for large data sets. So we grid our data outside OpenDX and use it only for visualisation.

Gridding algorithms can be found in various places on the internet, keywords are "b-spline", "kriging", "weighted distance" and "nearest neighbor" interpolation.

thanks for your opinions  Wink
 
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