Weld Command and UV map

[gap]

Hi there,

this is a problem I run across quite often: let's say that I am modelling an object composed of many identical modules adjacent to each other. What I would do, is creating just one of those modules, unwrap it and then duplicate/displace it as needed.
The problem arises when I combine and weld the duplicated objects: it seems that, besides welding the coincident faces, Wings also tries welding the UV projections of faces adjacent to the welded faces, screwing them up. Is there a way to avoid that, other than UV mapping each module separately after the welding process (with waste of time) or not using the weld command at all (with an avoidable increase of poly/vertex count in the final model)?

[micheus]

The problem arises when I combine and weld the duplicated objects: it seems that, besides welding the coincident faces, Wings also tries welding the UV projections of faces adjacent to the welded faces, screwing them up.

Just to be sure, are you talking about that distortion on the mesh we can noticed discretely close to the big cube?

[gap]

Just to be sure, are you talking about that distortion on the mesh we can noticed discretely close to the big cube?

Yes, I think your screen capture describes pretty well the problem I was talking about. Any workaround to avoid it happening?

[micheus]

Ok. That is something it seems nobody had noticed before.

I don't think so. I tried many options an I couldn't find a workaround.

When UV mapping an object usually the best practice is do that when it's finished - that means - we are not to change its topology anyway and we are doing that if using Weld. Maybe Wings3D should to look for this kind of situation - I'm not sure how this work in other 3D apps.

[gap]

When UV mapping an object usually the best practice is do that when it's finished - that means - we are not to change its topology anyway and we are doing that if using Weld.

I understand, in general that's my workflow too, but in my example UV mapping the object before cloning and welding it n times, is critically more time efficient

Maybe Wings3D should to look for this kind of situation - I'm not sure how this work in other 3D apps.

Wings3D is my main modelling tool, but at times, when I need a to perform a task not supported by Wings, I post-process my models in other 3D applications. The free version of Softimage XSI has a better implementation of the Weld command imho. It doesn't weld faces but couples of near vertices, it works well on UV-mapped meshes, with no UV map corruptions, an there is even an option for welding UV projections automatically.

[micheus]

The "problem" is the UV map coordinates is a vertices attribute, not a material one. So, by welding you are removing one of the two matched vertices from a face (like in my sample) - I think that could be the problem (but I can be wrong)

You probably will not smooth the object, so if you don't mind to have some extra and tiny faces close to the weld region then you could try to extrude a short amount the face that will be welded. But, use the Weld [RMB] and set the tolerance to a shorter value.
I'm not sure it would work, but you could try.

[gap]

The "problem" is the UV map coordinates is a vertices attribute, not a material one. So, by welding you are removing one of the two matched vertices from a face (like in my sample) - I think that could be the problem (but I can be wrong)

I see, it makes sense

You probably will not smooth the object, so if you don't mind to have some extra and tiny faces close to the weld region then you could try to extrude a short amount the face that will be welded. But, use the Weld [RMB] and set the tolerance to a shorter value.
I'm not sure it would work, but you could try.

No, I won't smooth it, it is a model I am creating for a videogame, but I want its geometry to be as clean and simple as possible. All in all, I think I will keep the duplicated polygons unwelded, or I will weld them using ModTool or MeshLab.

Here is a quick preview of the model I am working on by the way. It is the now destroyed old lighthouse of the Île de Sein, in France. My question applied to the railing and to lantern rooms's metal framework



Thank you for your feed-back anyway, I appreciate it

[micheus]

Nice work. Don't forget to share it with us at the Gallery session when you have done.

[gap]

Nice work. Don't forget to share it with us at the Gallery session when you have done.

Thank you!

Sure I will share it along with several other models that I have been working on during the last few years. So far I have been a bit reluctant to show my work here because most of my models are meant for real-time rendering, and they probably won't look as smooth as the models shared by other forum members

[micheus]

Don't worry about that.
By being Wings3D a modeller tool we like to see the meshes created with it. A beautiful render is a plus.