UV mapping: mapped polygons disappear

GTA:V Modding with ZModeler3 discussion.

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UV mapping: mapped polygons disappear

Postby V.T. » Tue Apr 18, 2017 1:09 pm

I am trying to UV-map a car (Bullet). I keep running into a problem that makes a UV-mapped set of polygons from a mesh disappear from UV-mapping window once I UV-map another set of polygons from the same mesh - in this case, 'bodyshell.'
In Bullet, 'bodyshell' is composed of all four quarter panels, a roof, a front bumper and a hood. So, I start from selecting a front bumper area:
Image

Now, I 'detach' with these options:
to new object OFF
keep original OFF
enable drag OFF

Believing the programme that it indeed detached the polygons (single click on the selected polygons), I apply the UV-map:
Image

Now, I would like to UV-map sides. So, I select all the left-side polygons and detach them:
Image

As soon as I assign a UV-map to the left side, the bumper disappears from UV-mapping window, even though I detached both the front bumper area AND left side from 'bodyshell':
Image

There is also a similar problem that some of the earlier mapped polygons disappear from the view once I get to UV-map a new group of bodyshell polygons - here, some of the left side polygons vanished after UV-mapping a hood:
Image

I haven't managed to make a working UV-map using the detachment method with all the 3 ticks off. How do I prevent these problems from happening?
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Re: UV mapping: mapped polygons disappear

Postby Oleg » Wed Apr 19, 2017 6:09 am

you should not change mesh topology while editing UV-mapping, as it can corrupt mesh mapping incidentally. when ZM detects topology changes, it removes objects from UV mapper that it considers to be potentially problematic, but it can leave some other uv fragments (that are still possible to be problematic). Literally, never use Detach/Weld/Attach on geometry when there are some mapping objects in UV Mapper window. The good way will be to detach needed fragments first (you can assign per-poly IDs to detached polygons, so you can re-select them quickly by ID later), and once everything is properly detached, start editing UV for these fragments. If you need to apply some mesh-topology tool, close UV Mapper (so it clears all uv-charts), apply tool(s) and apply Edit UV again ("Keep old" for old fragments and "Generate new" for new fragments) and continue your mapping work.
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Re: UV mapping: mapped polygons disappear

Postby V.T. » Wed Apr 19, 2017 10:47 am

I think I understand the concept to the degree, thanks - however, I will need to reapply it because I omitted a few polygons that messed up my mapping.

Also, is there a quick way to UV-map the lower LODs in the same way as L0?
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Re: UV mapping: mapped polygons disappear

Postby Oleg » Thu Apr 20, 2017 5:59 am

nope.
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Re: UV mapping: mapped polygons disappear

Postby V.T. » Tue Apr 25, 2017 8:56 am

After a few tries, I don't actually seem to know what to do, as I end up with corrupted mapping for "detached" parts, with stretched lines in the UV-map window. The car in question doesn't have a boot as-is - instead, it has a 'bodyshell' where a boot would be. Should I do it in this order?

0. Change the view to "Top".
1. Select desired bodyshell polygons (like a roof).
2. Assign a future livery material to the roof polygons.
3. Detach the roof.
4. Deselect the roof and select another bodyshell polygons (like a boot).
5. Assign a future livery material to the boot polygons.
6. Detach the boot.
7. Create a UV-map for the roof and the boot separately (since their polygons share edges), while still in "Top" view.
8. While being on full screen on UV-map window, change the view to "Perspective" and move on to another part of the car, like left side.
9. Select left side bodyshell polygons, assign material etc.

The actual order I made the mapping with might be different due to trying different methods.
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Re: UV mapping: mapped polygons disappear

Postby Oleg » Wed Apr 26, 2017 3:30 am

the best choice would be to attach/detach parts before you start mapping, so you can easily selected model fragments with Select \ Separated tool as needed.
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