[visit-developers] SR rendering without data decomposition

tom fogal tfogal at sci.utah.edu
Mon Oct 20 17:03:18 EDT 2008

Hi all, I've been working on the compositing-related problem for the
volume plot, in which arbitrary slices across image space seem to get
faded out.

I've been testing with 2 nodes. It seems the issue is that data are not
distributed to the second node, confirmed by a run with -dump producing
a blank image on the 2nd. My guess is that the two nodes composite,
blending together their two images, which is of course wrong because
the second node has no image data, thus it blends in white.

To fix this, I added some code to the network manager to detect when
only the root node has any data. In that event, we just pull the image
from the RenderGeometry call on process 0, and don't even run the image
composition process.

While that fixes the bug, it seems to break other portions of the test
suite.  Some images appear to be missing large `chunks', almost
assuredly because an entire domain is on the processor that I've
decided to ignore.

Is there any reason a plot would report no cells, or a VisWindow
report no primitives, and yet still have data to render?  What might
be a better test for this case?

(Yes, this points to some potential other bugs -- e.g. why does node 1
have no data? what exactly causes the composite not to either detect or
handle this case? etc. -- but I probably won't have time to look at
everything for 1.11.)



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