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[IDV #WNR-458825]: Problem w/volume rendering

Hi Katie-

> Hi Don. I have a few more questions concerning volume rendering I hope you 
> can help me with.
> 
> First off, a little background. I'm trying to do volume rendering of lwc 
> (liquid water content, clouds) over terrain. Each file is a netCDF file (80 
> meg) that has 1250x1250x50 points of liquid water plus 1250x1250 of terrain 
> elevation. There are 60 files total to be visualized (1 file=1min). There are 
> several problems I've been having:
> 
> 1) Even with 12 gig of memory allocated to IDV, often volume rendering runs 
> out of memory, even at much courser resolutions. Are there any parameters I 
> can change that will speed up the volume rendering?

Does the memory monitor actually show 12 Gb allocated?  Are you running a 64 bit
version of Java?  The 32 bit version will only allocate 2 Gb.

> 2) Sometimes IDV does not use the full 12 gigs allocated to it, but still 
> takes a very long time to render. Is this just because my data set is so 
> large?

Volume rendering is very much a hog of memory.  To do the volume rendering
we have to retransform the entire dataset.  If these are staggered WRF grids,
that will be even worse because we need to destagger them.

> 3) Occasionally, instead of getting the entire volume rendered, only a small 
> "chimney" will be visualized. It appears to be the full data set but only 
> over 1/20 of the proper area. Any ideas about what causes this? (Of course, I 
> can't get it to do it now, so I don't have a screen shot to show you)

I hate problems like that. ;-)  I can't think of anything off the top of my head
that would cause that.

> 4) Once the data is fully loaded, I can't seem to make the clouds look like 
> clouds. I want to control the volume to be colored by opacity, not color. If 
> the lwc is below a certain threshold value, I want those points to be totally 
> transparent (ie, want to be able to see straight to the ground). Any advice 
> on how to control the opacity in this way? (see attached photo of how our 
> clouds currently look; they are not very good-looking clouds)

The image didn't come across, but here are a couple of suggestions.  First, 
use the  Visible Range in the display control to set the range of the
values you want to visualize.  Alternatively (or in addition to), edit
the color table and set the transparency for the range you don't want
to see to 100% and the values you want to see to 90%.  That will make those
values you want to see more "cloudy".  Transparency is order dependent, so
if you have other displays in the View, you'll want to use the View->Bring to 
Front
menu on the Volume Control so you can see the other displays.

> Thank you so much for your time,

Don
> -----Original Message-----
> From: Unidata IDV Support [mailto:address@hidden]
> Sent: Thu 4/17/2008 5:34 PM
> To: Carbonari, Katie
> Cc: address@hidden
> Subject: [IDV #WNR-458825]: Problem w/volume rendering
> 
> Hi Katie-
> 
> > Full Name: katie carbonari
> > Email Address: address@hidden
> > Organization: northrop grumman
> > Package Version: 2.5
> > Operating System: linux
> > Hardware:
> > Description of problem: Hello. I've been trying to do some volume rendering 
> > of clouds in IDV. Isosurface works fine (as you can see in the attatched 
> > picture) but volume rendering gives a gray cube. This gray cube doesn't 
> > change when I change various parameters (color range, transparency, etc). 
> > Any ideas on why this is happening? The 2 pics are of the same data file, 
> > so I don't know why the volume rendering doesn't give clouds.
> 
> This is probably a graphics card issue.  What is the graphics
> card you are using?
> 
> Try the following:
> 
> - do the volume rendering
> - bring up the properties for the Volume Rendering control
> (Edit->Properties menu of the control).
> - Uncheck the Use Texture 3D property and click the OK button.
> 
> Does that make your volume rendering appear?
> 
> Don Murray
> 
> Ticket Details
> ===================
> Ticket ID: WNR-458825
> Department: Support IDV
> Priority: Normal
> Status: Open
> 
> 
> 
> 
> 
> 


Ticket Details
===================
Ticket ID: WNR-458825
Department: Support IDV
Priority: Normal
Status: Open