Bengt,
Hello and thanks for writing!
The error message you mentioned (_nul_tess unimplemented) pretty much
sums up the problem. To export any geometry to the STL format
requires tessellating the geometry and apparently tessellation of the
DSP primitive is not yet implemented.
It really isn't something that would be hard at all to implement
(could probably be done in an afternoon) but that probably doesn't
help you a whole lot.. Surprisingly enough, you're the first to bring
it up that I can recall. Can't say that I've ever even tried to
export myself. :-)
I've added it to the TODO for someone to hopefully look at and
implement soon. If you know how to code, I'd be glad to point you at
where in the source code you'd need to look to implement the
tessellation support.
Cheers!
Sean
On Sep 9, 2008, at 5:32 AM, Bengt Wennehorst wrote:
Dear BRL-CAD developers,
first of all thank you very much for this powerful free cad system!!
During a web search I’ve recently discovered brl-cad and installed
it at home on ubuntu 8.04. I am particularly interested in the dsp
(displacement map) feature and the g-stl translator, since I’d like
to use the results of height-calibrated microscopic fluorescence
measurements as input for cad modelling and further cfd
preprocessing (requiring stl-interfacing).
The dsp-feature seems to be extremely useful for solid-modelling of
my “microscale terrain data” and I’ve successfully used a 16 bit
RAW image file for dsp primitive creation.
However, trying to translate the database consisting only of this
object to stl format, the translator aborts due to tessellation
faults (modifications of the different tolerance values didn’t have
any effect). Error messages include something like “…_nul_tess
unimplemented” and “…boolean_walk_subtree…” (If necessary, I’ll
send you the exact messages). Using a simple sphere primitive shape
as the only database object, the translation was successful.
Since I wasn’t able to find any further details concerning the
creation and handling of dsp primitives (e.g. required input file
format - I identified raw by trial and error but I am not sure) and
the g-stl translation of those primitives (tessellation process and
possible problems/restrictions), I would like to ask if you could
give me some hints how dsps are properly being created and
translated to stl.
I would greatly appreciate your reply!
Best regards,
Bengt Wennehorst
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