[GRASSLIST:5481] NVIZ and GTOPO30 on osx

[Ian Macmillan]

Hi all, I have been trying to visualize a gtopo30 tile in NVIZ, but rather unsuccessfully.  When I load the tile into NVIZ the vertical exxagerration seems to be incredibly high.  When I try to draw the image with anything but zero vertical exaggeration, the mountain peaks become incredibly exaggerated or the image simply does not appear.  With zero exaggeration, the only wire mesh that shows is a single line that seems to be several thousand meters above the flat raster.  In addition, in some views with a z exag of 0.001 (the peaks are still really pointy), there are some "phantom" E-W trending dark bars that appear at several thousand meter (>10000m?) elevations.  Querying the data in NVIZ reveals correct elevations, it is just the image that is really distorted.

The DEM shows up in GRASS as a raster and a shaded relief (using an aspect map).  When I brought in the dataset I changed all of the -9999 values to null using r.in.bin (as signed integers).  r.info tells me that the elevation values are -79 to 4328 (as they should be), and everything looks right with this data in GRASS.  I have tried changing the region size (g.region) without any real success so far.  I have also messed with the polygon resolution with no real success.
 
I have gotten nviz to work in other locations with other DEMs, so I know it works on my machine, so I can't figure why I can't image this data.  Any ideas out there?

I am running GRASS5.0.0 on osx10.2.3

Any help would be great.  The mailing lists are pretty devoid of nviz info.

thanks, ian