Pamela Galli Posted June 12, 2014 Share Posted June 12, 2014 I made the unforgivable mistake of importing a .dae and joining it to another mesh without changing the name of the meshes so they match. Therefore, the meshes I worked on for several hours I have to re-UV and texture. Why did Blender coders make this change? What is the benefit? Link to comment Share on other sites More sharing options...
MIstahMoose Posted June 12, 2014 Share Posted June 12, 2014 I've never encountered that problem, When joining meshes it usually keeps the unwraps? Screenshot? Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 12, 2014 Author Share Posted June 12, 2014 We have discussed it before, and it was said there was an actual reason the coders did this. I dont remember what it was, but it would have to be pretty good for it to be worthwhile. If the meshes do not have the same name now, one of them is deleted, so there is not much to show in a screen shot. Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 12, 2014 Share Posted June 12, 2014 now i am confused. I thought you where refereing to the change about how UV Layers are merged when meshes are joined. Now you say meshes are deleted during joining ? Link to comment Share on other sites More sharing options...
MIstahMoose Posted June 12, 2014 Share Posted June 12, 2014 I just performed what you said.. And I still have my uv layous & materials for each mesh, Albeit in a jumble, but there? Maybe I am not understanding lol Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 12, 2014 Share Posted June 12, 2014 Blender provides multiple UV layers per mesh. These layers can be named. When 2 meshes are joined then this hapens: In older Blender versions: UV Layers are merged depending on their relative position in the list of UV-layers. When mesh A has 2 UV-layers and mesh B has 2 UV Layers, then the first UV layer of mesh a is merged with the first UV layer of mesh B, and consequently the second UV layers are merged in the same way. This was considered a completely wrong behaviour. It ONLY works when both meshes have the same number of layers, the same logical order of layers and when the layers are used for the same things. In newer versions of Blender (i believe since 2.70): Blender uses the names of the UV Layers to find matching pairs. and it keeps non matching UV lauyers separated. Now the user has the option to prepare the meshes UV layers such that the mesh join will create the correct UV Layer join. Does that make sense ? There has been a discussion if there could be some sort of UV Layer join tool that would be able to join and separate UV parts of a mesh. But as far as i recall nobody has worked on this yet. Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 12, 2014 Author Share Posted June 12, 2014 Well no I did not understand because I don't know about UV layers. I just separate UVs by material. I dont know the purpose of UV layers. Mistah, make two meshes. Change the name of the UV Map of one. Then join them. One of the UV maps will disappear. Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 12, 2014 Share Posted June 12, 2014 A mesh can have several UV layers for many purposes. Where each UV Layer contains a UV Map. Just take this as a fact of Blender When you join 2 meshes where each mesh has only one UV Layer and when both meshes have named the UV Layer differently, then the joined mesh will have 2 UV Layers. You find the UV Layers in the Mesh data properties section... When both UV Layers have the same name, then the joined mesh will get one joined UV Layer. This new behaviour is better compared to the behaviour of older blender versions, where UV Layers where always joined undependent of their names. Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 12, 2014 Author Share Posted June 12, 2014 Are you saying there is a way to salvage the disappeared UVs Gaia? Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 12, 2014 Share Posted June 12, 2014 We would need a "join UV layers" function... hmmm... Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 12, 2014 Share Posted June 12, 2014 i just got a tip for how you could do it. Actually all you do is separate the object into its original parts, remove obsolete UV Layers, rename the remaining UV Layers to the same name, join: edit the joined object. select all verts which are connected to the first UV Layer separate this mesh as seprate object. (use 'p') take care to rename both UV Layers in Both Objects to the same name join the objects Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 12, 2014 Author Share Posted June 12, 2014 That does not work, Gaia. When separated, one of the UVs no longer exists. Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 13, 2014 Share Posted June 13, 2014 Sorry that i could not be of help in this case, but then obviously i also do not understand what your problem is. Maybe you deleted one of the UV maps while you where working in the joined object ? Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 13, 2014 Author Share Posted June 13, 2014 What happes is that one of the UV maps collapses into a dot in the bottom left corner of the UV space. I can send you an example file if you like, using the same process I described above. Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 13, 2014 Share Posted June 13, 2014 Pamela Galli wrote: What happes is that one of the UV maps collapses into a dot in the bottom left corner of the UV space. I can send you an example file if you like, using the same process I described above. This collapse happens when you separate the objects ? Could you publish a demo blendfile that shows the model just before the UV map collapses and then explain what exactly you do, that results in the collapsed UV map ? http://pasteall.org/blend would be a good service to use for publishing ... Link to comment Share on other sites More sharing options...
Drongle McMahon Posted June 13, 2014 Share Posted June 13, 2014 "the UV maps collapses into a dot in the bottom left corner" That's what you get when no UV mapping has been applied. All the vertices are mapped to coordinates 0,0. Even before the change to name matchng, if you combined two meshes with different numbers of UV maps, in one of them the mesh with fewer maps will never have been mapped, and all it's vertices will consequently be 0,0. With the name matching, I suppose the same thing still happens - wherever a mesh had no map with the name of one from the other mesh, all it's vertices will be 0,0 in the combined map. There is no need to have different UV maps for different materials. In fact, it is not a good idea for SL import because SL will only ever use one map, even if there are more in the collada file. So you need to have all the materials included in one UV map. Unless you are baking all materials into a single texture for SL, you can select by material to map each separately to the same UV map. That way, the whole UV space will get used for each material (by default) and the material maps will overlap, but that doesn't matter because they are going to be textured separately. To bake, just use a new image in the UV panel after selecting each material, then bake. You don't need a new UV map. The important thing here is to keep in mind a clear distinction between the UV map and the baked images. They are not the same thing. They are independent. On image can be used at the same time with different UV maps, and one UV map can be used at the same time with different images. Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 13, 2014 Author Share Posted June 13, 2014 I just tried reproducing it and, voila, cannot. I even tried with the same two meshes that this happened with yesterday, and could not reproduce it. I notice I am using 2.69. So, clearly I am hallucinating that upon joining meshes with different names, one collapses into a corner. And also hallucinating that when I take it inworld and apply a texture, the mesh turns black (which is how I am tipped off what has happened.) I hallucinate this about once a month, after importing a mesh and joining it with another. Sorry for taking up people's time with this repeatedly, you are always so helpful. :-) Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 13, 2014 Share Posted June 13, 2014 When it happens again report it to Blender https://developer.blender.org Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 13, 2014 Author Share Posted June 13, 2014 These two meshes had been mapped. I had used them both on other projects and was combining them for the new project. I had imported one into the file. But as I say I cannot reproduce it on purpose now. I do have all the materials in one UV map (except in advertantly when I join two with different names). I was trying to understand what the UV layers Gaia mentioned, are used for. My "layers" are by material, as you said here: "To bake, just use a new image in the UV panel after selecting each material, then bake." Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 13, 2014 Author Share Posted June 13, 2014 Thank you I will do that! Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 13, 2014 Author Share Posted June 13, 2014 Finding some info: https://developer.blender.org/T37182 https://developer.blender.org/T37577 I am not hallucinating after all, yay! Here is one comment: " bug only happens (as far as I can see) when you create the UVmap of the first cube in Edit mode, leave back to Object mode, and do not switch again first cube in Edit mode. Else, joining works as expected. So I suspect a sync issue in CDLayers between Object and Edit modes, somehow… Will dig this next week. PS: Following steps above allow to recreate the bug, if you really create first cube from scratch (using the default-scene one does not work). And to make joining work as expected, you just have to tab one more time in/out Edit mode for the first cube, before doing the joining (after or before duplicating to the second cube, that does not matters)." Like I am going to remember that haha! Link to comment Share on other sites More sharing options...
Gaia Clary Posted June 13, 2014 Share Posted June 13, 2014 oh, a 2.69 bug ... bah. So you work with old and outdated software But seriously ... this is another nice example for how important it is to tell which software version is used... I should have mentioned that i was testing on 2.71 release candidate, while you should have mentioned earlier that you use blender 2.69 So.. next time we all know better Link to comment Share on other sites More sharing options...
Pamela Galli Posted June 13, 2014 Author Share Posted June 13, 2014 LOL I would say I have learned my lesson but I had previously learned my lesson re not using the newest release of something until I was sure it was safe. But since 2.7 will soon be old, I will consider it safe :-) Link to comment Share on other sites More sharing options...
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