"Chris B" <nom### [at] nomailcom> wrote:
> "Mr" <nomail@nomail> wrote in message
> news:web.4a81df0e4068d214e3f0b2880@news.povray.org...
> > ...
> > Actually, there should'nt be any triangles since they are just extruded
> > vertices
> > forming a long uninterrupted continuous series of edges like a spline
> > without
> > interpolation. (hair)
> > so they should'nt be arrays of 3 edges... only pairs one after the other.
> > I
> > feel it should be easier to convert those to actual geometry on blender
> > side.
> > but eve if I don't make it, it's not worth the effort. It's not as if hair
> > didn't get exported, just some of its curlyness set up into its child
> > particles.
> >
>
> Ah! Ok. My first assumption was all wrong then.
>
> There definitely are triangular faces in the file snippet you posted,
> although it's not possible to see whether the triangles are degenerate,
> because you only show the first vertex and I'd need to see the first 3
> vertices to be able to say whether the first triangle is degenerate (two or
> more vertices in the same place).
>
> I now assume you're creating a surface and extruding the vertices in
> Blender, then exporting as an 'obj' file that you convert to POV-Ray using
> the excellent PoseRay utility written by FlyerX.
>
> If this new assumption is correct, then the sample you posted must have
> contained some sort of surface defined in Blender when you exported it,
> otherwise you wouldn't get any faces in the mesh2 object.
>
> When you export to Wavefront-obj format from Blender, the generated 'obj'
> file contains a set of 3 and/or 4 sided faces to represent surfaces and a
> series of 2-sided faces for the straight-line segments.  If you then convert
> this to POV-Ray using the PoseRay utility that FlyerX wrote, it converts any
> 3 and 4 sided faces into triangular faces within a mesh2 object and ignores
> the 2-sided faces. This means that any 'hairs' created as extruded vertices
> forming a "long uninterrupted continuous series of edges" will be lost and
> you will end up with only the original surface from which they were
> extruded.
>
> The good news is that the 'obj' file format can give you the 'edge' data you
> would need to reconstruct the 'hairs' in POV-Ray. To display these in
> POV-Ray you'll need a script to go through the 'obj' file looking for
> 2-sided face definitions and adding a POV-Ray cylinder to represent each
> 'edge'. Here's a simple 'obj' file I exported from Blender, having created a
> 4-sided face (a plane) and extruded the 4 vertices. I then extruded the
> first of those 4 vertices a second time (f 9 5) giving a total of 5 edges.
>
> # Blender3D v248 OBJ File: linetest2.obj.blend
> # www.blender3d.org
> mtllib linetest2.mtl
> v 0.970005 -0.000000 -1.014998
> v 0.970005 0.000000 0.985002
> v -1.029996 0.000000 0.985002
> v -1.029995 -0.000000 -1.014998
> v 2.334797 -0.000000 -2.424784
> v 0.445084 0.000000 1.599909
> v -1.554916 0.000000 1.599909
> v -1.554915 -0.000000 -0.400091
> v 3.969549 -0.000000 -3.174670
> usemtl (null)
> s off
> f 1 4 3 2
> f 1 5
> f 2 6
> f 3 7
> f 4 8
> f 9 5
>
> The 'obj' file shows the resulting 9 vertices. The 4-sided face uses
> vertices 1, 4, 3 and 2 and the five extruded 'hairs' are each represented as
> a 2-sided face. Writing a simple script to create a set of straight-line
> cylinders to represent these Blender 'edges' should be fairly
> straight-forward. If you wanted to get more sophisticated it would be
> possible to match up adjacent 'edges' to create a nice smooth spline, but
> this is likely to be significantly more complex.
>
>
> If you used some other way to generate the code snippet you posted, then it
> is possible that it contains a sequence of degenerate triangles representing
> just the 'edges' (the 'hairs'). This would need a different solution to be
> able to see make it visible in a POV-Ray scene.
>
> Regards,
> Chris B.

Thanks For this very well explained tip on faceless edges in obj format.
Although I'm using Blend2Pov instead of the Obj export, the problem seems to be
much more simple: after checking up again, what I had copied was another mesh
of the scene. The faceless mesh didn't get  exported at all.

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