Split an UV-mapped object into smaller parts and smaller UV maps?

[skote]

Hi, I'm new to 3D coat and just checking if this is the right program for me.

I have a number of 3D-scans that I need to split to smaller objects to use in a game, for example a human where I need a separate .obj and a separate UV-map for each limb. I can do this in C4D which I normally use, but then each individual part still uses the whole UV map from the original objects, even though it's only a few islands that are actually being displayed, which is a waste of space. I've managed to import my scans and split them up in 3D coat, but how do I go about assigning the new objects new UV maps with only the relevant bits? 

Thanks a lot!

[Carlosan]

Hi

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:

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.

[skote]

Thank you @Carlosan it works well! Do you happen to know if there is any way of exporting separate objects as .obj from 3DC? Right now it combines all my elements into one mesh in export so I need to do each element in a separate file, which is quite time consuming. 

[Carlosan]

Exporting as fbx file helps to separate ?

[skote]

Yes, that works!

[houGenie]

On ‎16‎.‎11‎.‎2017 at 11:00 PM, Carlosan said:

Hi

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:

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.

I have tried this procedure. But the normal map is not recalculated for paint room it seems, when I change the UVs in UV room. Any idea why ?

[Carlosan]

Try this please.

Dont press Apply UV-set in UV tab.

Switch back to Paint and only apply changes there

 

[houGenie]

@Carlosan: Thank you for the tip, but it did not help. But it looks different now. I can provide you a file if you want to look.

[digman]

I am back at the fourms now too. There is a way to get the desired result.

Access to your file for downloading would be helpful to show you.

[houGenie]

Ok thanks. What I want to do is to pack the UVs in the scene file. There were previously more meshes in the scene file which I deleted. Now I want to assign the free UV space to the left object. The file is compressed, otherwise it would be about the limit. Thanks for the help!

magazine2.7z

[digman]

I will now try to understand this change.

You deleted the sculpt layers but left the hidden retopo objects... Do you need them anymore? If not delete them.

I will tell you what I did based on what I think you want now. 

I created a new uv set named magazine. 

I selected the Retopo object layer named magazine. Next at the bottom of the panel the icon for select all faces on that layer, I used.

I next selected Move Select and moved the said faces / uv-islands to the new Magazine UV set. 

Unwrapped  the uv -set and prepared for baking but I did not bake. 

Now having gave a method, I am not sure what your desired workflow is. Do you only want to bake the Magazine and not have any other model in the 3DC scene.  

If you only want the magazine model, delete the hidden retopo objects including the plane and then remove the unused Uv sets. Same drop box you use for creating a new uv set.  

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If you desire to have the gun model with all the sculpt layers and retopo objects. 

You can create as many uv sets has you need and move the selected faces / uv-islands using the method describe.  There is a method for baking multiple Uv sets and overlapping model parts to prevent occlusion artifacts.

If you use Skype for screen sharing and voice communication, I can help you faster there as you will have more questions, the above will depending upon your workflow bring up more questions.

Note: Sometimes 3DC will just simply refuse to delete one unused UV set, there is a workaround for that.

You have a problem on the model, you can see the red face in the uv-set. I would check it out and see what is causing it.

 

Edited December 3, 2017 by digman

[houGenie]

@Digman: What I want to do is to delete all objects but the magazine and spread the magazine islands to the whole UV space (0..1). All paintings I have done in the layers (painting room) should be preserved but use the new UV arrangement. Normally you would do that in the UV room and then go back to paint room. But when I do that, the magazine looks weird, it must be ther normal map:

[digman]

In order to preserve the normal map you must do the below when preserving the normal map layers. This is when you update the UV set. 

After moving the magazine uv-islands to the new uv-set you must use PackUV2. It only scales and moves the islands for a better fit. Any rotation or flipping changes the normal vectors thus messing up the normal map.  This does not apply to textures but only for normal maps. If your model does not have a normal map then any unwrapping will work, That is just for information. 

In this case because of having a normal map only use PackUV2. 

If you get stumped, pm me if you use Skype and we can setup a session. I do this to help as I volunteer my time and Skype can be just faster than instruction through typing.

Edited December 3, 2017 by digman

[houGenie]

18 hours ago, digman said:

In order to preserve the normal map you must do the below when preserving the normal map layers. This is when you update the UV set. 

After moving the magazine uv-islands to the new uv-set you must use PackUV2. It only scales and moves the islands for a better fit. Any rotation or flipping changes the normal vectors thus messing up the normal map.  This does not apply to textures but only for normal maps. If your model does not have a normal map then any unwrapping will work, That is just for information. 

In this case because of having a normal map only use PackUV2. 

If you get stumped, pm me if you use Skype and we can setup a session. I do this to help as I volunteer my time and Skype can be just faster than instruction through typing.

Yes! This works. Thank you very much for your effort. But I do not get it. I thought there is a recalculation anyway, so why is a rotation of the islands relevant ? Why does a rotation of an Island change the normal vector ? I thought only the color information is used to store the normal vector (a difference vector to the vertex normal to be precise).

Edited December 4, 2017 by houGenie

[digman]

It has been a few  years since talking to Andrew through e-mail about this subject. I addressed the issue to him but I can not remember all the details from that dialogue. Main thing is we have a way to update and keep the normal map and textures when updating our uv sets if necessary.  

 

[Carlosan]

Try Textures > Texturing Baking tool

This tool allows you to get projections of normal.

Use it to bake old model to new model.

Hope it help

 

[houGenie]

Thank you for the infos, I will try it. 

[digman]

One problem with the Texture Baking Tool is that it still does not support PBR exporting.  I would have mention that method as well if it did. If you only need a normal map or the old gloss/spec workflow then it is fine to use.

Also if you are just exporting textures from a high polygon scanned mesh to a low polygon mesh that has a normal map already that works as well.  This a workflow I use at times.

I mention a number of times that it needs to be updated to include a PBR workflow...

Edited December 5, 2017 by digman