Re: undersampling points in vizualization

• To: Tom Nelson <tanelso@xxxxxxxxxxxxxxxxxx>
• Subject: Re: undersampling points in vizualization
• From: Bill Hibbard <billh@xxxxxxxxxxxxx>
• Date: Mon, 20 May 2002 14:59:34 -0500 (CDT)

Hi Tom,

The undersampling happens because VisAD uses texture mapping
by default for effciency. You can disable it by:

  GraphicsModeControl mode = display.getGraphicsModeControl();
  mode.setTextureEnable(false);

You can also limit the degree of undersampling with texture
maps by:

  mode.setCurvedSize(int curved_size);

Good luck,
Bill
p.s., visad-list-digest is not working, but our system
admins are working on fixing it.
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html


On Mon, 20 May 2002, Tom Nelson wrote:

> Greetings,
>
> I have just started using VisAD. I want to visualize
> a 'terrain' of data samples, say 100x100 in longitude
> and latitude, with various height values.
>
> I modified P4_01.java from the tutorial to do this.
>
> I also added option buttons to allow me to set PolygonAttributes
> to POLYGON_FILL, POLYGON_LINE, and POLYGON_POINT, and to
> also setPointMode(true) or (false) on the GraphicsModeControl.
>
> When I setPointMode(true), I see all of my data samples.
> When I attempt to show a 'terrain' (POLYGON_FILL) or a grid
> (POLYGON_LINE) there is an undersampling of my data points
> leading to an incorrect display.
>
> I see the same effect with the original P4_01.java code
> when I add my components to change the PolygonAttributes
> and/or the PointMode. The 50x50 samples are reduced to 25x25
> in the POLYGON_LINE and POLYGON_POINT mode.
>
> I've been digging into the source code to track down just where
> my samples are converted to Java3D objects, and I've also
> looked in this list archive for previous question about this.
>
> Ideally, I'd like to have control over whether my data is undersampled
> or not. I just haven't stumbled on the obvious way to fix that!
>
> Tom Nelson
>
>
>
>

• References:
  • undersampling points in vizualization
    • From: Tom Nelson