Support for exporting curves in .OBJ and/or Collada formaat

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Germ
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Support for exporting curves in .OBJ and/or Collada formaat

Post by Germ »

Hi!

As per the trailing discussion in https://forum.freecadweb.org/viewtopic.php?p=652924 ,I was hoping for the curved surfaces on my model to be exported as such in Wavefront .OBJ or using the Collada exporter

There is one to represent curved surfaces in both formats:

For .OBJ: I was wondering if we'd do it the same as for https://github.com/FreeCAD/FreeCAD/issues/6008
vm4dim
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Re: Support for exporting curves in .OBJ and/or Collada formaat

Post by vm4dim »

https://martinreddy.net/gfx/3d/OBJ.spec
This specification was proposed / published 15 years ago.
But section "Free-form curve/surface" remains unrealized.
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Germ
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Re: Support for exporting curves in .OBJ and/or Collada formaat

Post by Germ »

vm4dim wrote: Thu Jan 19, 2023 1:42 am https://martinreddy.net/gfx/3d/OBJ.spec
This specification was proposed / published 15 years ago.
But section "Free-form curve/surface" remains unrealized.
Thank you for your reply!

When I started looking for `surface' I found almost the entire document being about it.
I'll start looking deeper. What I wonder is if there is another modeller to use for tests. I suppose any would do
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Germ
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Re: Support for exporting curves in .OBJ and/or Collada formaat

Post by Germ »

So I see what you mean with the section not specified @vm4dim

I keep running into references of it being supported though, i.e. https://docs.fileformat.com/3d/obj/#free-form-surfaces

Initially I was going to create a git issue over this but now I am not too sure

FWIW there is a similar thread on the Blender forum: https://devtalk.blender.org/t/nurbs-imp ... rt/17581/7

Also I know AutoDesk isn't necessarily a reference but Alias's reference also mentions curves/surfaces supported in .OBJ https://knowledge.autodesk.com/support/ ... -html.html
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Germ
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Re: Support for exporting curves in .OBJ and/or Collada formaat

Post by Germ »

FWIW, http://www.uhu.es/francisco.moreno/gii_ ... J_SPEC.PDF has the "Free-form curve/surface section.
But again Idk anymore I feel pretty alone on this :)
heda
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Re: Support for exporting curves in .OBJ and/or Collada formaat

Post by heda »

yeah, making parsers for proprietary file formats is a lonely path to walk.
probably not that hard to do the fc part of it, but without documentation of the other side, you will have to reverse engineer a format that they can (and do) change in a whim from year to year. most of the proprietary formats have binary blobs in them, and without full docs, well it is anyones guess what that blob actually means...

with that said, if you have an itch to scratch - by all means do it.
you can probably find some macros dealing with imports of surfaces, for example in iges.
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Re: Support for exporting curves in .OBJ and/or Collada formaat

Post by Germ »

Thank you! I will create an issue and report
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Germ
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Re: Support for exporting curves in .OBJ and/or Collada formaat

Post by Germ »

OK we are not yet one year in :D:

From bugging Blender about the same [1] I have been made aware of Ayam, which seems to support those features (NURBS in Wavefront .OBJ files.)

I am (gettit ? :P) trying to compile it on my NetBSD.
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