UV Mapping Warping Issues

M

MMounteer

0
Hi everyone,

I keep having issues with the UV mapping in Cheetah. Most of the time it does as expected but I'm not going to lie, it often times feels like a black box to me where I just kinda hope it works.

I have a simple model here and made (what I felt) were some reasonable cuts to UV map this object. The problem is that it seems to warp one side of the object more than the other and also doesn't scale things appropriately as you can see.

Screen Shot 2022-03-17 at 6.46.43 PM.png


Does anybody have any idea why this could be happening?

I'm also wondering what the difference is in the Unwrap with LSCM and Unwrap with ABF options?

Thanks and looking forward to any and all replies!
 

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I´d try the UV-mapper on polygon selections then instead. If it´s a symmetrical object I´d delete one half and add with the symmetry-modifier back in place - that should give identical UVs you can place on top on each other in the UV editor to save space.
While LCSM UV unwrapping (least-squares conformal maps) seems more suitable for organic shapes and tries to maintain equal quad topology ABF (Angle Based Flattening) works better on hard surface models (industrial and architectural design).
UVmapper.png
 
MMounteer said:
...
Does anybody have any idea why this could be happening?
Click to expand...

I don't do much mapping, but I have a theory. The surfaces on the long side of your model has a series of indentions, closer to the top than the bottom. I suspect that if you look at each point on the top edges of one side, you'll find that they are not PERFECTLY aligned. I'm talking one or two thousandths of a unit off or less. The other side IS probably aligned, which could be why you got a rectangle on one side and boomerang shape on the other. Understand that the numeric interface display is actually a rounded value compared to the number being used in C3D's internal math. Grab those points and flatten that line using the scaling tools, both laterally and vertically, just squish them into alignment even though they already appear to be lined up. ( Trust the math ). Then try mapping it again.
 

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MMounteer said:
Hi everyone,

I keep having issues with the UV mapping in Cheetah. Most of the time it does as expected but I'm not going to lie, it often times feels like a black box to me where I just kinda hope it works.

I have a simple model here and made (what I felt) were some reasonable cuts to UV map this object. The problem is that it seems to warp one side of the object more than the other and also doesn't scale things appropriately as you can see.

View attachment 38314

Does anybody have any idea why this could be happening?

I'm also wondering what the difference is in the Unwrap with LSCM and Unwrap with ABF options?

Thanks and looking forward to any and all replies!
Click to expand...
hi how can I change the color dark mode of cheetah ? white mode is bad for eyes
 
MonkeyT said:
I don't do much mapping, but I have a theory. The surfaces on the long side of your model has a series of indentions, closer to the top than the bottom. I suspect that if you look at each point on the top edges of one side, you'll find that they are not PERFECTLY aligned. I'm talking one or two thousandths of a unit off or less. The other side IS probably aligned, which could be why you got a rectangle on one side and boomerang shape on the other. Understand that the numeric interface display is actually a rounded value compared to the number being used in C3D's internal math. Grab those points and flatten that line using the scaling tools, both laterally and vertically, just squish them into alignment even though they already appear to be lined up. ( Trust the math ). Then try mapping it again.
Click to expand...
I think you are on to something here. I looked into it and they definitely were skewed. I didn't realize that the UV mapper is so sensitive (not sure if sensitive is the right word but it does appear to have fixed the issue. I did as frank suggested and used symmetry and now they seem to be correctly aligned. Thanks for your reply!
 
frank beckmann said:
I´d try the UV-mapper on polygon selections then instead. If it´s a symmetrical object I´d delete one half and add with the symmetry-modifier back in place - that should give identical UVs you can place on top on each other in the UV editor to save space.
While LCSM UV unwrapping (least-squares conformal maps) seems more suitable for organic shapes and tries to maintain equal quad topology ABF (Angle Based Flattening) works better on hard surface models (industrial and architectural design).
View attachment 38316
Click to expand...
Hi frank, I did give this a go and had better luck although selecting the polygons was a little bit tedious. The symmetry modifier worked like a charm though. I gotta learn to use the UV Mapper tool better now tho because it really is a life saver.

Also thanks for your definitions! I have been wondering that for some time now and wasn't able to find it in the documentation although I suspect I just missed it.
 
MMounteer said:
Hi frank, I did give this a go and had better luck although selecting the polygons was a little bit tedious. The symmetry modifier worked like a charm though. I gotta learn to use the UV Mapper tool better now tho because it really is a life saver.

Also thanks for your definitions! I have been wondering that for some time now and wasn't able to find it in the documentation although I suspect I just missed it.
Click to expand...
This should not be too elaborate. "Group select" can select UV islands in one click in the UV editor. Or in 3d view you go into Top-view and use Area-Select and with cmd + Ring-select you can subtract the other parts.
 
While Frank is entirely correct, it's sometimes well worth to try both LSCM and ABF on some objects. In the past I've had sometimes better results with LSCM on hard edge models and ABF on organic shapes.

Also, you should look into pins in Cheetah. You'll find some posts where Frank explains the use of them.

Probably the most important thing is to get an UV checker map, a texture usually with squares and numbers, that will help you to control the uv map visually for distortion and stretching. You can then change it accordingly (it's somewhat astonishing that still so much has to be done by eye). You will find a map of your liking using any search engine with the keywords "UV checker map".

Also it's a question of the use case for the object you are uv mapping. For painting, for some other external tools and so on you can get away with a streched map or an atlas map (for most cases that gives you way to many islands). Some tools (like Substance painter and to my knowledge armor painter (I'm not so sure about that, though)) can create their own map automatically (it's usually distorted like hell, but in such a tool it doesn't matter).

By the way, there is a reason most people in 3d hate uv mapping. Sometimes it eats up way more time than the modeling itself. So I cheat the hell out of it, do not use one if I can somehow get away without, and sometimes use more than one map (with different seams) so I can cover for example scratches on edges easily that on the other map are parted. At the same time, of course, you need exercising the mapping, so you're getting faster.
 
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