Re: [brlcad-devel] I am new to the brl-cad world

[Christopher S. M. <br...@ma...>]

On Aug 12, 2010, at 12:26 AM, Jean-Luc Delatre wrote:

>
> I would suggest using http://openscad.org/ to create the geometry
> and importing the STL into BRL-CAD for whatever else you want to do.

Wow.  I wouldn't.  That would be exceptionally counter-productive if  
you intend to use the geometry for any analytic purpose (including  
ray-tracing, which he indicated).

Geometry format transformations are lossy.  Conversion to polygonal  
is usually the worst preserving, increases the data requirements by  
about two orders of magnitude, and often introduces completely new  
problems such as interferences, holes, and solidity failures.  You  
want to maintain a faithful representation and not change formats.

It, of course, entirely depends on whether the intended geometry  
purposing is entirely just visualization or limited by some other  
tool chain being used.  In that limited case, STL (i.e. polygonal  
boundary representation) might be an acceptable format to import from  
but rarely ever is that the case.  Otherwise, OpenSCAD doesn't offer  
*any* capability that BRL-CAD doesn't already provide and has it's  
own problems (e.g., OpenCSG will fail on a real-world model).

The natural option I left out I thought was obvious.  In addition to  
writing scripts or C/C++ code, one could model the geometry  
interactively using our geometry editor.  That will preserve data in  
compact implicit form and be robust for analysis purposing.

Cheers!
Sean