Two bevel modifiers, but only one messes up the UVs. Why?

I have basically a box, where two sides needs to have a large bevel and the rest of the sides only very small ones. Yet, the small ones (which cover all of the model) play nice with the UV mapping, but the large one in the bottom right corner of the video messes it up:

Anyone know why? Is it because a new ngon was created on the side? This is 2.8, so I would have hoped that it would be a bit more intelligvent in preserving the mapping…

EDIT: If I go into edit mode and bevel, I’m fine as long as I create a chamfer… but the moment I increate the segments, the UVs go crazy for that new ngon. :frowning:

EDIT 2: Worth noting is that he UVs go crazy in a different way after I apply the bevel. So perhaps there’s hope that the live modifier could perhaps be updated to play more nicely with the UVs in the future?

Such error is possible. You can use data transfer modifier to copy uvs , basically duplicate the original box and use it as the source.

it looks like your smaller bevel is wrapping around the corner, rather than creating a round corner. That round corner generates a big ol’ n-gon which can be tricky to keep the UV’s straight.

Is this a case of using the new miter options in bevel? I (bevel developer) admit to not having looked hard at what happens to UVs with them, yet.
Also there is a long-standing problem that if you use an odd number of segments, it is hard to get bevel to make consistent choices that “look good”. But I don’t think from your video that that is the case here. If it is not that kind of problem, you can submit a bug report and I will look at it.

1 Like

That sounds interesting, but I failed to find a tutorial for this. If I search for “data transfer uv” I get either only tutorials for the modifier, or tutorials for copying uv maps. I haven’t seen a tutorial which shows how to project uv maps from one object to another using the ray cast option, which I believe is necessary here (especially if I want to keep the original mirror modifier which I already applied in the above example).

I’m never sure what is a bug and what is a feature request when it comes to blender bug reporting (most of my bug reports get closed as feature requests and being told to go to rightclickselect).

Here, I wonder if it’s the bevel modifier not playing nicely with the subdivision modifier, not respecting islands, or not respecting seams (I tried this actually, made no difference):

  1. Live modifier


2. Applied modifier


3. Manually corrected corner UV map

I cannot tell what is going on from screen shots. I need a .blend file.

I know it is difficult to tell whether something is a bug or a feature request in Blender. Often, though not always, it is a bug if it used to work in an older version of Blender but not in the newest one. If we had a perfect and perfectly detailed specification of what each feature and tool in Blender was supposed to do, then the test for “is a bug” is just “it doesn’t do what the documentation says”. Unfortunately we have nowhere near a complete specification of what stuff is supposed to do. I once tried, for Bevel, but it turns out to be really hard to anticipate and document everything that might happen with such a complicated function.

So, the sad state is, if you are unsure if something is a bug or a “working as intended”, the best course is to report a bug (pro tip: use the “Report a Bug” menu option under the Help menu at the top of Blender; it has recently been updated to prefill in all of the OS information needed; and as always, the most essential thing to do is include a .blend file in the bug report). And if a developer says, “sorry, closing as ‘working as intended’”, try not to feel bad.

1 Like