Breaking model while retaining UV map and textures?

[Shawn Driscoll]

Is it possible to import an OBJ mesh that is already UV mapped and textured (diffuse, bump, spec image maps) and divide the mesh into three separate pieces, then export as OBJ and the UV mapping and textures still work with each piece?

[johnnycore]

Yeah it should be possible.. import model including textures into paint room, go to uv room to create new uv maps textures are automatically updated to new UV's when you apply the new UV's.

Next step is to export model with new uv's including textures and then you should be able to split them in your 3D app..

[AbnRanger]

You could do the same in your 3D app as well. Just detach the elements you want to separate. It shouldn't break the textures or UV's.

[johnnycore]

You could do the same in your 3D app as well. Just detach the elements you want to separate. It shouldn't break the textures or UV's.

Oh yeah ofcourse.. its better to do it this way I tought 3 seperate models + 3 seperate textures.. which comes in handy in some cases..

[Shawn Driscoll]

You could do the same in your 3D app as well. Just detach the elements you want to separate. It shouldn't break the textures or UV's.

I don't know if my modeling apps will let me bust apart models without scrambling their vertex order and UV mapping.

[johnnycore]

Which modeling app are you using?

[Shawn Driscoll]

Old ones. Silo. Hexagon. modo, which I can't stand modeling in.

[AbnRanger]

I don't know if my modeling apps will let me bust apart models without scrambling their vertex order and UV mapping.

I know in 3ds Max, you can break them up like that, without losing anything. When you apply a UV Unwrap modifier to the individual object, you won't see the islands from the other object. Only the ones for the current object, but their placement and scale is unchanged in the UV map.

So, it's essentially the same as what Johnny was telling you. You can simply select the islands of the separate objects, and move them to their own UV Sets. Once hit APPLY UV SET, you should now have 3 sub materials in the (object) materials panel. When exporting, it should be the same result as separating them in your 3D App.

Nevertheless, if you want to do them in 3DC, you have a lot of flexibility to change your UV maps and still keep the textures intact:

[johnnycore]

Modo should be able to do so eaily, you can also use Houdini very easily.. the Apprentice version is free for non commercial use, and it lets you do everything what the full version does except for rendering.. you might wanna check that one out.

[Shawn Driscoll]

So if I had a simple egg mesh that was already painted in some easter egg coloring, I would not be able to import it into 3D-Coat 3.7.18 (latest beta) and divide the mesh into a few parts (say the egg broke or something) and have each one retain a part of the UV mapping so they don't lose their textures?

I'm still learning 3D-Coat in this area. I supposed I could learn how modo would handle it. I only use modo for rendering. Not for any UV mapping or texturing.

[johnnycore]

You can try importing the model three times in the retopo room (if you want to divide it into three pieces) and then, and then delete the faces from eachother untill you've got three pieces.. not 100% sure if it works dont have 3dcoat on this computer currently.. but you can try this..

[AbnRanger]

So if I had a simple egg mesh that was already painted in some easter egg coloring, I would not be able to import it into 3D-Coat 3.7.18 (latest beta) and divide the mesh into a few parts (say the egg broke or something) and have each one retain a part of the UV mapping so they don't lose their textures?

I'm still learning 3D-Coat in this area. I supposed I could learn how modo would handle it. I only use modo for rendering. Not for any UV mapping or texturing.

When you create 2 additional UV maps and move the islands of the parts you want separated, you get the same result. That is effectively what happens when you split your model in an external 3D App. They get their own UV map, but the faces/verts all stay in the same location on their UV map. So, for example....let's say you had a character with all the parts on the same UV map. If you detach the head, arms and legs, as separate objects...when you look at their individual UV maps, their islands would be in the same location...only difference is that you have a lot of blank space where the other parts used to be.

If you import you model into the retopo room, you can separate the the different parts by creating blank layers for those, select the poly's then click the little icon at the bottom of the panel that lets you "move selected faces to current layer."

You now have different Retopo layers, but all are still on the same UV map. Merge to the Paint Room and now import your textures (Textures > Import). You will have one model, but separate sub-object (material panel) layers.

[Shawn Driscoll]

I'm understanding some of this. I'm visualizing that I'm watching a YouTube video of the process so I know what I'm doing.

[AbnRanger]

I'm understanding some of this. I'm visualizing that I'm watching a YouTube video of the process so I know what I'm doing.

Well, here's another one to visualize, then.

[digman]

If you want to break apart the mesh but keep the existing UV in Hexagon, use the "Dissociate tool" in Hexagon. It is highlighted in the picture. Check your export settings to make sure do not re-merge points(vertices) again on export...

The above will get the job done but how well it renders in an application that has a smoothing routine for the model, I could not tell you. I guess it would depend the application and whether you do any smoothing or not...

Multiple UV sets would be better in most cases as AbnRanger pointed out and you get more texture space for your diffuse, spec, normal maps etc...

[Shawn Driscoll]

Clever. I forgot about that tool. Does 3D-Coat have such a tool?

So the mesh is still one object. Just in parts. That may work. I was thinking I'd end up with three objects. modo 401 was not being friendly with OBJ exporting for me. I love how 3D-Coat lets you export an OBJ with texture maps, and then turn around and let you import the OBJ and it scoops up all the texture maps that come with it. modo only semi-imports texture maps with OBJ models, and doesn't export texture maps at all with new OBJ exports. Its MTL file is blank for all practical purposes.

[digman]

Yes, the model is still one object not three...

No Dissociate tool, like that in 3DCoat.

Also if you import a model into 3DCoat that is broken apart as we have discussed, then you have to do the below:

In the import dialog box choose Auto-smoothing-Groups and set it to "0" otherwise you will get rendering errors...

There will be no smoothing applied all.

To see the rendering errors do not use auto smoothing groups and you will see what I mean.

[Shawn Driscoll]

If I can get the mesh broken up, I won't need to use the model in 3D-Coat again after that. The model will be in pieces anyway, so it won't matter if the poly edges of the pieces don't smooth just right.

I'm going to download Hexagon 2.5 whatever from DAZ now. I'm not a fan of the program, but if it works....

Anyone know if Silo 2.2 does the disassociate thing?

ADDED:

I just found Silo's BREAK feature. So maybe I don't need to fuss with buggy Hexagon 2.5. I just need to keep in mind that the models I break up need to stay as one object as far as my rendering app is concerned.

[Shawn Driscoll]

The BREAK command in Silo 2.2 creates two objects from one. Each object has its own name. But they both retain UV map information. So I figured, "Hey, doesn't Hexagon 1.21 have that same feature?" So I loaded my model in it and used the Face Extraction tool. It did the same thing. Split one model into two and each model keeps its UV info. No vertex re-ordering, or UV map scrambling. So I am good with that.

What's really cool is how I can then import the broken model into 3D-Coat and do an off-the-cuff auto-UV mapping and my painted textures are still in their right place using all new UVs.

ADDED:

I did the same thing in modo 401, using the "Create null mesh, then cut/copy/paste piece of model into null mesh, then drag mesh to texture mapping folder (and/or assign existing UV'd material to dragged mesh)" method. Painful. Modeling in modo is like driving a car where you have to enable your turn signal first before the steering wheel will unlock and be able to turn only in the direction of the turn signal you enabled.

It too creates more than one model when the split is done. And it keeps the UVs intact.