Re: .g File Conversion
Christopher Sean Morrison <brlcad@...
2013-11-06 03:47:23 GMT
You've reached the right place, hopefully I can be of assistance. Be aware, though, that what you ask is quite a complex topic.
So sorry to hear about your conversion difficulties. There are indeed many tricks to overcome the complexities involved, but there is no set recipe. The dominant factors that affect conversion success are the tolerance settings, the structure of the geometry involved, the complexity of any boolean recipes, and the particular export method being used (they are not all equal).
There are ways to influence all four of those which will affect the output quality.
For tolerance, most all of the stand-alone BRL-CAD export tools (like g-iges and g-obj) have flags that let you set the absolute (calculation), relative (calculation), normal (curvature), and distance tolerance. These have HUGE impact on quality, conversion time, and success rate. The easiest way to learn how they work are to take a simple region and play with different settings. Try setting relative to 10 degree or 1 degree. Try setting absolute to 0.01 or 0.001 (default is 0.0005). There are limitless possibilities.
That said, I'd also suggest not using the g-iges converter as it's one of the most complex converters in BRL-CAD. The g-obj or g-dxf or g-obj might be a little easier to manage. Since you mentioned the scripting option, you should also be aware that we already have/provide a script that converts a .g model region by region. See the facetall.sh script or the facetize_all_regions command in mged (which is what the script calls).
That's a lot to hopefully help you get started, but be aware that this is a complex topic. If it could easily be made turn-key, we would have made it that a *long* time ago. There is rarely a conversion that cannot success by adjusting the conversion tolerance settings and model configuration, but knowing what to change and how to change it is very complicated.
Please reply back with any questions you have. I'll try to answer what I can and hopefully help reduce some of the frustration.
p.s. As a glimmer of hope, be aware that we know that we are working to make this a LOT easier. We've spent years implementing advanced nurbs/brep/step infrastructure that completely changes the fundamental method of conversion so that it's much more reliable for export. Advancements are due to be announced over the next 3-6 months.
On Nov 5, 2013, at 8:15 PM, Johnson, Lynsey E. wrote:
I am writing to request a contact for software support in the area of file conversion for the BRLCAD 7.24.0. The g-iges executable command produces models with many flaws, and I am wondering if there are any tricks to improve the quality of the converted files. My division is in desperate need of reliable file conversion, so much so that we are attempting to create a shell script that converts .g models by region.
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