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[IDV #GHK-711416]: Error with display of contour lines in head on view (video included)

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  • Subject: [IDV #GHK-711416]: Error with display of contour lines in head on view (video included)
  • Date: Tue, 22 Apr 2008 13:40:26 -0600
Hi again-

> Full Name: Hrobjartur Thorsteinsson
> Email Address: address@hidden
> Organization: Icelandic Met Office
> Package Version: 2.5b2 build date:2008-04-22 07:05 UTC
> Operating System: Linux
> Hardware: Java: home: /home/hroi/local/share/IDV_2.5b2/jre version: 1.5.0_11 
> j3d:1.5.1 fcs (build6)
> Description of problem: I get a bug with the display of contour lines over a 
> colour filled surface.
> The contour lines are invisible when viewing the map head on, but are
> visible from any other angle.
> 
> Please observe my demonstration video of this effect (14 MB):

> 
> The data that I am plotting is a forecast model in WMO GRIB format,
> please find the data and the bundel file here:

> 
> I notice that this effect doesnt seem to occur with the demonstration
> data sets provided in NetCDF format.

The issue here is that the 2D grids are really 3D grids at a fixed height.
So the pressure is rendered at 0 meters and the temp at 2 meters which
puts the pressures behind the temperature.  With the default vertical
range (0 to 16 km), the z ordering is hard to determine, so as you
rotate, sometimes the contours show through.  They are always visible
from the bottom since they are actually below the temp.  If you change the
vertical range to something closer to the data (e.g. 0 to 50 meters),
you'll see that they are separated.

The only solution I have at present is to use the make2D() Jython 
procedure that takes a one level 3D grid and converts it to a 2D
grid.  You could either make a formula to call this (the formula
would be make2D(a) ) or just use the Grids->Define a Grid Diagnostic
and put in make2D(a) for the gddiag.   Then select your temperature
field and it will be rendered at the same level as the pressure.

We have talked about adding in a feature to the plan view controls
to allow the user to "ignore" the vertical dimension and move the
display up and down in the box.  But I don't think I'll get that
in the next release.

Thanks for your kind words about the IDV.  We are glad you find it
useful.

Don Murray 

Ticket Details
===================
Ticket ID: GHK-711416
Department: Support IDV
Priority: Normal
Status: Open