Re: [visad] Strange rendering depending on axis range

• To: visad@xxxxxxxxxxxxxxxx
• Subject: Re: [visad] Strange rendering depending on axis range
• From: Tom Rink <rink@xxxxxxxxxxxxx>
• Date: Thu, 24 May 2012 15:59:36 -0500

Tomas,

Thanks to some debugging from Ghansham Sangar (SAC/ISRO) and plots
from Chris Pudney, this indeed looks like a precision problem manifested
in the surface normal generation. The double-precision Set classes won't
help with this.  To help verifiy this is the case, you might try

Tom

On 5/22/12 9:27 PM, Pudney Chris (ext) GBJH wrote:

G'day,

Here's another example of the issue Tomas is talking about (from the MZmine software).

The artefacts appear when the sampling resolution along the m/z axis is high (attachment 1).

They're not present at lower resolutions (attachment 2).

Floating point precision could well be the issue.

Regards,
Chris.

On 22/05/12 08:11, Tomas Pluskal wrote:

Hi Tom,

Thank you for the tip.

I would like to try that, but what class should I use instead of the Linear2DSet? There seems to be only Gridded2DDoubleSet, but no equivalent for the linear set.

By the way, please check the other batch of screenshots I sent: http://www.unidata.ucar.edu/mailing_lists/archives/visad/2012/msg00057.html There the same issue appears although the spacing between the data points is not so close (around 1).

Tomas


On May 21, 2012, at 10:41 PM, Tom Rink wrote:

Hi Tomas,

With the Linear2DSet you've defined, the points are pretty close, maybe

too close for single precision. You could try the double-precision version

of the Set classes.

Tom

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    • From: Tom Rink
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    • From: Tomas Pluskal
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    • From: Pudney Chris (ext) GBJH