[MBDyn-users] Blender+MBDyn-0.4.7_with_NetCDF_Interface-0.0.1.zip

doug at baldwintechnology.com doug at baldwintechnology.com
Tue May 10 17:22:24 CEST 2011


Patrick,

Looks good. Packaging NetCDF in a separate Python module is smart. As for
performance, I'd suggest first testing Python standalone for various
formats, block sizes, etc, assuming you later will write a C++ routine to
create such a data format. A better approach might be to compile in C++ a
Python module that presents the data to Python from C++ managed memory. As
you progress, test the Python code inside of Blender to see any
performance impacts or functional issues, especially if shared memory with
C++ is an option.

By the way, Python has an iterate() method, which is nice for traversing
AND indexing a list of objects (no need to keep track of a count++). I
expect we'll be able to seamlessly integrate into the import_mov and
display methods calls to your NetCDF module.

Doug


> Hi Doug,
> hello MBDyn users,
>
> please find attached version 0.4.7 of your scripts with a first draft of a
> Python NetCDF-interface included.
> I'm using the NetCDF-IO-routines included in  SciPy  .
>
> The interface is working on my machine but only on modified MBDyn - ".nc"
> - files that have no empty character variables
> any more. With unmodified MBDyn NetCDF output the  SciPy  routines fail
> for some unknown reason, though they should not:
> I checked  the .nc  files created from MBDyn  with  'ncdump'  and
> 'ncBrowse'  and both programs had no problem in
> reading (and displaying) the files, so it must be something specific to
> SciPy's  NetCDF routines.
>
> The variables causing the problems in MBDyn's .nc files are in the
> variables section e.g.
> variable:
>    ...
>    char node.struct.12(vec1) ;
>       node.struct.1:type = "dynamic" ;
> while in the data section the variable's data are empty (..what should be
> allowed in principal)
> data:
>    ...
>    node.struct.0 = "" ;
>
> Removing these variables from the .nc file fixed the problem (can be done
> using 'ncdump' or 'ncdump4mbdyn' and 'ncgen').
> Having removed these import is working also as either DOUBLE or FLOAT and
> even on larger files with many steps and variables.
>
> Maybe it's better/safer to change MBDyn's .nc output and rather define
> these informal kind of data as global attributes instead of variables,
> as the variables in MBDyn's nc-output should be more related to be
> time-dependent (i.e. having dimension 'time') in contrast to the char-vars
> which only reflect the structural node's type (dynamic/static).
>
> Another point that disappointed me is that I found the binary import in
> Python to be rather slow.
> Can you tell me if you get the same (bad) performance ?
>
> Best regards,
> Patrick.
>
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