polygon meshes (again)

Next
 From:  okapi
2447.1 
Hi Michael,
I know you have said that it would be a lot of effort to create an importer for polygonal models,
or also to create a translator from polygons to nurbs.

Would it be as difficult to convert a model made up of quad and triangles into a set of nurbs, so that each face is a nurbs surface (tri or quad) ?
So all polygonal curved models would be translated as a serie of nurbs quads or triangle surfaces.
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  Paolo (PAOLOLOBBIA)
2447.2 In reply to 2447.1 
Hi okapi,

I used the MeshToNurb command
in Rhino.

I tested the model in the image below.
But even with a MeshAngle set to 40
degrees, it turned out slow to move
and rotate.
Image Attachments:
Size: 133.9 KB, Downloaded: 63 times, Dimensions: 793x556px
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  okapi
2447.3 In reply to 2447.2 
Hi Paolo,
I am thinking about this not for organic forms actually, but for simpler geometries (floor slabs, cubes etc....),
so more for objects mainly composed of planar faces.

The main issue for me is that I often work with 3d models of buildings provided by my clients.
Some of these work in Rhino, but others can only provide me with polygonal meshes.

It would be good to be able to import these as surfaces, to be able to work on the further in moi, or even to have them as reference.
I know you can import a wireframe into moi, but it would be better to have surfaces.
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  Paolo (PAOLOLOBBIA)
2447.4 In reply to 2447.3 
Hi okapi,

I understand your message.

I tested the model in Moi and it rotates and moves fast !
So i correct my previous message.

(I forgot Moi is different)
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  okapi
2447.5 In reply to 2447.4 
ok, thanks for testing out that this works in Rhino;
maybe this is a way to do it. Ideally I would like to have a process that bypasses Rhino though.
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  PaQ
2447.6 In reply to 2447.5 
As usual I'm with Okapi on this one, looks like we have the same kind of workflow. I often rebuild models from draft poly object, and for the moment I have to do printscreens in my poly software and use them as images reference in MoI.

I have tried the _meshtonurbs in rhino, but it's not that great on mid-res models (5000+ polys), MoI can handle it easily, but the wire curves slow down the viewport a lot on this kind of modelds. But maybe layers will allready help a lot, if it's possible to put the meshnurbs'reference one a layer and hide the curves for this layer.
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  Michael Gibson
2447.7 In reply to 2447.1 
Hi Okapi,

> Would it be as difficult to convert a model made up of quad and
> triangles into a set of nurbs, so that each face is a nurbs surface
> (tri or quad) ?
> So all polygonal curved models would be translated as a serie of
> nurbs quads or triangle surfaces.

It's not too difficult to implement as far as writing the code, but unfortunately it does not tend to produce very good results except for in the special case of a model that is supposed to be faceted like a diamond for instance.

NURBS models are generally intended to have curved surfaces made up of larger smooth single surface sheets and it does not fit very well into the overall NURBS structure to have geometry that should be smooth instead be diced up into a lot of little tiny planes.

I actually added a command for that in Rhino, called MeshToNurb as described above.

However, check out this post from someone who currently works on Rhino support - he wishes that it would have never been added because it causes a lot of problems and tends to lead people down a path giving bad results...

So I'm not exactly too excited to go down that path... But if you really do need to do that now, Rhino's MeshToNurb (or I think Sycode.com has a mesh to solids program also) can do exactly that kind of a process.


Eventually maybe I'll be able to figure out some better way to handle polygonal data imports. Maybe if I had a special command that was for importing "reference geometry" or something like that rather than having it in the regular Open file list.

- Michael
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  Michael Gibson
2447.8 In reply to 2447.3 
Hi Okapi,

> I am thinking about this not for organic forms actually, but for
> simpler geometries (floor slabs, cubes etc....),
> so more for objects mainly composed of planar faces.

Yeah actually for this kind of stuff it would work.

Unfortunately this is kind of a special case - typically it is just a lot more common for polygon mesh files to contain more organic types of shapes which does not work well for this kind of a thing.

It's kind of a problem to have a tool which will most frequently be used in a way that does not work well and only in special circumstances will do the right thing... That's sort of my general worry about it at any rate.

- Michael
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  jbshorty
2447.9 In reply to 2447.7 
Michael you beat me to it. I was going to point to that same Rhino discussion. True, such a command can create some potentially bad situations if someone imports a non-manifold mesh without knowing it. But I have found that command to be very useful in Rhino. And probably it has practical use for archviz work. For example, you could easily import a Sketchup model, run MeshToNurb, then run MergeAllFaces to get a clean nurbs model on boxy geometry. But it takes some knowledge of the mesh you putting in before you do it! I guess many of the problems occur when the mesh is created first by someone else... Either way, I don't much see the point of converting something organic like that "pighead?" to be all planar nurbs faces. It's kind of useless, except as reference. So might as well just import a mesh, and forget converting to Nurbs...

jonah
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
Next
 From:  okapi
2447.10 In reply to 2447.9 
Thanks for the info.
I see it pretty much as jbshorty:
this is not for importing organic forms into moi, but rather to import basic geometries as references.
I do mainly arch viz.
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged

Previous
 From:  Michael Gibson
2447.11 In reply to 2447.10 
Hi okapi, sure I understand that.

And what will probably work better is if in the future I can add a polygon mesh object type as another kind of object in MoI, rather than trying to convert polygons to a bunch of little NURBS planes as the primary way to bring OBJ data over. (which is what you seemed to be asking about in the start of this thread)

If for example I added an OBJ import to the regular File/Open and File/Import commands that would do this kind of polygon-to-faceted-NURBS processing, it would get used by quite a few people for trying to bring in organic forms anyway, even though it would not work well for that. Pretty quickly I would be getting questions why opening OBJ files results in 200MB NURBS files that are totally unwieldy...

That's why that one particular method of conversion to NURBS is difficult to set up as the main way to handle polygon reference data, it would probably tend to work better if polygon data would stay as polygon data for the general case.

- Michael
  Reply Reply More Options
Post Options
Reply as PM Reply as PM
Print Print
Mark as unread Mark as unread
Relationship Relationship
IP Logged
 

Reply to All Reply to All