Re: Data not rendering as IsoContour

Hi Russell,

If you are willing, you may be able to diagnose this problem
yourself. First, make sure you are using the latest source
from the VisAD ftp server. You'll want to run from compiled
source, so you can insert print statements. The focus should
be the makeContour() method of visad/ShadowType.java. At about
the 83rd line of this method there is a line:

  if (bvalues[0]) {

Insert a print of bvalues[0] before this - it should be true.
If it's false, then you want to focus on visad/ContourControl.java
and why mainContours (the source of bvalues[0]) is false, by
inserting calls to DisplayImpl.printStack("your message here")
at the various places where mainContours gets set (stack dumps
are useful for understanding the circumstances under which
bvalues[0] is being set).

If bvalues[0] is true then, back in ShadowType.makeContour(),
you'll want to make sure spatialManifoldDimension == 3 (so it
will try to make an iso-suface) and that fvalues[0] (the level
for the isosurface) has a reasonable value. Print fvalues[0]
before:

  if (fvalues[0] == fvalues[0]) {

at about the 101st line of makeContour(). If fvalues[0] has
an unreasonable value (NaN, or the minimum value of the Field
are likely unreasonable values), then insert calls to
DisplayImpl.printStack("your message here") at the various
places where surfaceValue is set in visad/ContourControl.java

Please let us know what you find.

Thanks,
Bill


On Tue, 12 Aug 2003, Russell Steicke wrote:

> Hello,
>
> We have a strange problem with ScalarMaps and rendering with IsoContour.
> Under certain circumstances the data will render correctly, but most of
> the time the data will not be displayed at all.
>
> We've tried to duplicate the behaviour with a simple example, but
> haven't been able to do that.
>
> The symptoms are that when we have data mapped to IsoContour, nothing
> will be displayed.  If we then add a ScalarMap from D to RGB or Red or
> Green or Blue or ZAxis, where D is any data that is actually present on
> the display, all the IsoContour mapped data will appear, including data
> unrelated to D.  We can also make the IsoContour mapped data appear by
> explicitly calling setContourInterval() on a ContourControl, which will
> make _all_ the IsoContour mapped data appear, not just the data
> associated with that ContourControl.
>
> There are obviously workarounds here, but it would be better to find out
> where the problem lies.  Does anyone have any ideas about this?
>
> Thanks
> Russell
>
>
> --
> Russell Steicke
>
> -- Fortune says:
> What does it mean if there is no fortune for you?