>
> Rakshika,
>
> 2016-03-30 19:35 GMT+02:00 Rakshika Bagavathy <
> rakshika.bagava...@gmail.com>:
> > Hello Sean and Daniel,
> >
> > After reading your inputs on the task, i have a few questions:
> >
> > 1. Daniel mentioned that some additional features of bots that might be
> lost
> > in conversion. I'm unable to understand what those are. Also, all the
> > algorithms i mentioned in the proposal use just the basic vertices and
> faces
> > (with indexed vertices) as the input. So, what are those extra features
> that
> > we don't want to lose? either way, while returning a healed polygonal
> mesh
> > structure we can just change the vertices, faces, and normals (if
> required).
>
> Please have a look at struct rt_bot_internal in include/rt/geom.h.
> Did you understand all entries of this struct? How about OpenSCAD? I
> know nothing about its internal structures, but I'm pretty sure that
> e.g. the polygonal mesh (how many do they have?) isn't trivial.
Yes, i have looked at it and understood the entries. I'm looking through
the OpenSCAD primitive (which is in class PolySet, as i found). I do
realise that they are not trivial. What i meant to say was that, after we
convert a bot/polyset to the intermediate structure, we preserve the native
structures, work on the intermediate structure, and while converting it
back we'll need to be primarily changing only the vertices and faces and
other things such as normals and face normals can be computed, and some
other things like orientation, mode, etc. will still remain the same, which
can be used for topology correction. Am i missing something through this
approach?
>
>
> > 2. Sean mentioned that there will be topology changes, but as far as i
> > think, it won't matter much because we are going to be healing them after
> > those changes, right?
>
> Changes the topology doesn't necessarily mean that a mesh is broken.
> Think at a perfect mesh. "Healing" it should change nothing, but
> applying conversions to it could perhaps change the order of triangles
> or the order of vertices in a triangle. Could this cause problems?
Well, i don't think there would be problems when we convert from bot to the
intermediate structure (with just vertices and the faces with indexed
vertices), as we go from more information to less information. I'm not too
sure about the OpenSCAD primitive, still looking into it. If we're
converting from the intermediate structure to bot, if we followed the
method i mentioned above, would it not be fine? Essentially, if we
performed the topology corrections alone native to the two organizations
separately, the geometric operations can be combined through the portable
module.
>
>
> > So, would it be fine to go forward with an STL like format which can be
> > inter-converted to both BRL-CAD and OpenSCAD's primitives?
>
> It depends. Can you write converters which don't damage the mesh?
> How much time would you need to do it?
Please review the method i mentioned above. Time required to code might
depend on that.
>
>
> Did you understand the alternatives?
Yes i did. The method with compiler switches would essentially mean writing
the algorithm twice, right? Wouldn't the same problem come with the base
and derived classes as well? Using the intermediate structure seems like
the most efficient way possible.
>
>
> > Or, we could first solve all topological defects and then use the
> half-edge
> > data structure (as non-manifold meshes are the only ones that cannot be
> > represented by a half-edge data structure, am i missing anything?) to
> > correct all the other defects. Whichever one is the most optimal would be
> > fine.
>
> This sounds like doing the second step before the first one: Solve
> defects, but with which structure?
How about what i mentioned above: Solving the topological defects (singular
vertices, singular edges, orientation inconsistency) for both the
structures separately and performing only the geometric defects removal in
the portable module?
Sorry if i'm going about anything the wrong way.
Regards,
Rakshika.
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