UV unwrapping/baking woes, and fundamental confusion -- free mesh attached

Attached is a ‘well’. I’d like to unwrap and bake the lower/stone portion, but I’m having troubles doing so.

It may be because, as modeled, there’s a hole in the mesh IF you separate the wooden bit from the stone bit. It’s like the stone bit is a plastic shell, w/2 holes in it. So that’s one possible issue.

The other is my problem: I have a fundamental confusion with how UVs are handled in Blender. It seems (to me) that every Face is a portion of every UV map. I’m used to a different system that supports a Face-by-Face assignment of polys (Faces) to a UV map, and a UV map can have as few as zero faces as ‘members’. I’m just not seeing how Blender separates out the Faces from the UV maps.

Anyway, here’s the mesh. Enjoy! Feel free to use it if you like, it’s nothing special.
WellONLY_.blend (982.4 KB)

Maybe this will explain my fundamental confusion to some extent:

I made a toroid, then selected some few Faces on it. Going in the UV workspace I made a blank image , and used UNWRAP on those few Faces. At that point, I could see the UV mapping of the selected faces. This is as expected.

What throws me into confusion is the display when I select ALL the Faces: all the Faces are present in the UV map. :astonished: :astonished: :astonished: This is a foreign workflow for me: what do people do with all those unwanted Faces? Are they compressed and dragged off to the hinterlands of the texture map?

You are probably used to UDIM tiles in other software.

In Blender, UDIM support is new. It was added in 2.82.


So, by default, an UVmap in Blender is a map of the whole mesh where exists one UVFace per face.
When you synced selections between UV Editor and 3DView, only UV faces of faces selected in 3D View are shown in UV Editor.
But that does not mean that unselected polys don’t have corresponding UVFaces in UVmaps. They are just not displayed.

To be able to assign an Image only to an UVIsland ; you have to create UDIM tiles.
At that moment, each tile can be filled by a different image and dedicated to one UVIsland or one UVface of UVmap.

Wrong: I know nothing of UDIM. And, have no use for them. So, no.

OK. So I see another layer of confusion here. And I completely understand. Damn… it has been so long.

So yes. When you add a UV map in Blender it basically assigns UVs to the entire Mesh. Unlike LightWave where you can simply add UV data only to a selection.

If you get into a situation where you want to have some UVs not affected by a texture you will have to select those faces and assign them to another material that will not use the texture and not get any UV mapping. Or if you want to have it get uv mapping with with another texture.

In this case you UV will overlap if they are all selected at once. And the UVs will be used by their assigned materials.

Hope that makes sense.

Thanks Richard, your patience is appreciated.

I think I’ll wait 24 hours to let this all sink in b4 asking any more questions. :wink: --Well, about UVs at any rate.

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Hey man, when you are done unpacking your brain, maybe I can whip up a tutorial on UV mapping. It is on a long list of things to do.

Let me know if that will be useful.

It will probably give you more ammo to complain about how things work… ha ha ha

And that can’t be bad in the end. Right…? lol

But seriously. It isn’t a perfect process. But there are some great plugins I can share that really help. Also I have developed some techniques that basically demystify the process.

Still working on it. I found a very comprehensive YT video, BUT the problem was the presenter, although having stellar results, overcomplicated everything to 'wayyy beyond what I could digest.

And I’m still confused, I think because of my LW conditioning, as to how different UV maps are stipulated for given textures and/or Material Settings. Almost surely overthinking it. Should probably forge ahead and hope it all gets clearer via simple projects.

There’s some sort of interplay between a given UV map and the ‘slot’ system, which I find particularly baffling - the ‘slot’ seems like a useless complication to assigning Materials. In LW terms, ‘slots’ are a bit like ‘Parts’ - a Face can only belong to one Slot, as a Poly can only belong to one Part, but in Blender Materials are assigned to Slots…blah blah blah…

There’s also this confusing Blender thing where, if you create a single Slot, >all< the Faces are assigned to it, no matter what the Selection was. This is bulls!t: what they should have done is decree “there is ALWAYS one slot!” and just made it visible from the start, instead of magically adding everything to something the user creates. They pull the same stunt with the “virtual default material”.

Really, they are rubbish at UI.
EDIT: currently working on ‘decals’.

Yeah it took me a while to get around the slots thing as well. Took me a while to realize it is surprisingly similar to LightWave, having to have a default material. Or put it another way you have to have a material on everything. There is no such thing as just select some faces and there is your material the first time. LightWave forces this on you as well. If there is only one material it has to be on everything.

This is standard in any rendering system. An object cant have no material on any faces. That is how it renders. And that you can see it at all in a render is only because there is a fall back material.

LightWave forces you to use Default Material on any faces you don’t assign. And if you don’t assign any, the whole object gets the default.

Blender takes it a step further back and supplies a default Material you basically can’t see exists.

It is just one of those things you have to digest. That in Blender when you add the first material, it will be the one that gets all faces. Any materials after that have to get assigned from a selection.

OK. I made a wrong assumption.
But that does not change the fact that if you try UDIM, you will probably consider this workflow more close to how you are used to deal with UVs in lightwave.

In Blender, a Slot is a generic term used each time you encounter a list in UI.
Material List is made of Material Slots.
Render Tests list is made of Render Slots.
When you paint textures inside Blender, Textures List is made of Texture Slots.
Particle Systems List is made of Particle System Slots.

Material Slots are not different from what you wrote.
A face can only have one material. It is only assigned to one material slot.
By default, all faces are using material in first material slot.
If there are already several material slots, newly created faces by subdivision, extrusion, are assigned to material slot used by faces they were generated from.
But if you had new faces by adding new primitive from shift A menu, they are using first slot material.

A material slot is a container for a material. That means that if you are not happy with material in material slot, you can simply put another material in it.
You don’t have to redo any grouping of faces for that.

So, one face is only using one material. But a material can use as many UVmaps as textures.
But concept can be compared to a Google map.
You are searching for a street. But you know that if you zoom out, you will see the city and continue to zoom out the country and the whole planet.
If you select a face in 3D View, you only see UV face corresponding to the face.
If you select a part in 3D View, you only see UV face corresponding to the part.
If you select all faces in 3D View, you only see UV face corresponding to the whole mesh.

You probably have already seen deformed world maps for statistics purposes where countries having more of one type of resources than others are represented bigger.
For each statistic, you end-up with a different world map.
That is not different.
For different purpose of mapping, you will have different UVmaps.

To continue this analogy, UDIM tiles are the way to cut your world map into pieces.
And you can dedicate an UDIM tile to an UVIsland or Face like you would dedicate page of a geographical index to a country or a city.

The problem with only assigning a UV to a single face of an object in LW, is that its a hack and not a proper way of working with UV’s. It looks like only one face is in the UV map in LW, but look at the 3d view how it wraps the image.

Now export as obj and load it in Blender and see it looks the same, It was not UV mapping only that face it did all faces but hide it from you.

Don’t mind the image, it was cheap. :rofl:

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In Cycles, reset all, select the face you want to keep, select inverse, move UVs outside. Then set the image to Clip and Alpha output can be used with procedurals if needed. Baking emission (just a noise texture), the single face was baked down to texture.

I know a lot of this is “that’s just the way it is (get used to it)”, but damn, so much of it seems bass-ackwards.

Yeah, and I think that is silly. It exists, just name it and use it, don’t make the user go thru this charade of creating one. Same with the first Material slot.

I guess I’ll just grit my teeth and try to handle it.

On to a maybe better class of confusion: in this test blend:
UV toroid.blend (759.2 KB)
(hmm, that file seems mighty small for a packed file, lemme know if it works)

…there are 2 materials, 2 slots, and 2 UV maps. In this screenie,

moving the indicated UV point around doesn’t move the texture in the 4 affected Faces. Why would that be?

Hi @Jeric_Synergy,

You’re materials are both referencing the same UV map ( the 1st) - specify which specific uv map a material uses with a node:



Thanks for that info: Is that (nodes) the only way that Blender differentiates between UV Maps for different materials? 'Cuz that was a huge question I had: how are different UV Maps specifically associated with different materials?

And if the answer is “it defaults to the first in the list, but can be switched via nodes”, that clears up a lot of questions (or maybe just one big one).


As far as I know, or use it, yes, that is the only way to make a specific material use a specific UVmap. By default every standard piece of mesh geometry once created has a default UVmap, which is usually very clean in its layout.


I agree. Maybe they are in the process of changing that. I noticed that the Cube comes with a Material and a UV map now by default.

That would help. But if you are coming from LightWave and you ever delete that material you would be back at square one again… lol

So, also understand my approach with helping you is hopefully an even dose of reference back to something you are familiar with (which always helps me when I am leaning), in LightWave. And then trying to explain the explainable. Things I was finally able to get my head around after hours of banging my head against the wall.

If there is anything I have in my favor, it is not necessarily smarts. I am just dogged and persistent. And I have a way to simplify things - hopefully - for others once I have actually figured it out.

But if there is anything I have learned in these last years of 3D, it is being able to accept that, this is “rome” now. So I think it is just a matter of having a visa for Italy but don’t give up your citizenship from where you came from. And visit home often… lol

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By default, I believe it will select the first in the list yes. But the way you assign a material to a particular UV Map if you have many is to select the map here:

You may also do this in nodes. And everything you do in this panel will also hook up nodes for you in the background.

Like this:

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When you don’t precise an UVmap in material, default UVmap used in Viewport is :

  • for Material Preview or Rendered mode, the one with the Render icon enabled in UVmap list.
  • for Solid mode, Texture color, the one active, highlighted in UVmap list.
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Yes, I’ve perceived that, and appreciate it. It’s a little bit discouraging how one’s perceptions are shaped by one’s initial exposure to… waaaaaitaminit, I didn’t have ANY trouble w/c4d’s approach to the same thing. Nah, it’s Blender.

I’d definitely be better off it was the first 3d s/w I’d ever used, kinda like you don’t know your first gf/partner is rubbish until you get another, better one. I’d say Blender is a bit like a bad girlfriend/partner, except less expensive. 'WAYYY less.

Like you, I’ll continue to beat my head against this wall, because it’s the one I can afford. I’m keeping a document that records my travails, and could eventually excerpt all the LW-centric stuff out of it, if anybody’s left from LW-land to make it worthwhile. AND, I’ve channeled a lot of energy into RightClickSelect, so the people here don’t have to put up (so much) with my whining. Many of my suggestions are well received.