Manifold problem and difference between UV Set in UV room and Paint room

[Stefka]

Halo community.

I´m using 3DCoat 2023.41

I do have an issue with the manifold problem in 3DCoat. Beside the thought, if this function is clever, even so it might be useful in cooperation with other programs, I would like to solve my problems by myself and not let 3DCoat delete part of my models. But this is not the topic of this post.

Here is what happens on my side, when I do have a manifold problem in my model.

This picture shows the area, where the manifold problem appears. There had been some inner faces, which caused the problem. Little bit hard to identify. (Bild1) 

In the Modelling room I edited the mesh by deleting these extra faces and adding a new face. Looks pretty good (Bild2)

This picture shows the mesh in Modelling room. Special interest is the area in the upper left corner. As you can see, there are no lines coming from anywhere of the mesh. (Bild3)

As you can see the mesh is still correct in the Paint room (Bild4)

As well in the UV room (Bild5)

Model also still looks good (Bild6)

As you may have realised in (Bild3), some of the edges are soft edges and wrong. To edit this I go back to Modelling room and add some sharp edges. (Bild7)

Returning back to Paint room, shows the positive result. (Bild8)

Than I go to UV room for unwrap. As you can see the UV mesh is still ok. (Bild9)

HERE COMES THE PROBLEM

When I go back to Paint room, the UV mesh is different to UV room. In Paint room, as you can see there are suddenly lines going from anywhere in the UV mesh to the upper left corner, crossing other islands. (Bild10) and this caused texturing errors in the model (Bild11)

In UV room these lines to the upper left corner are not there (Bild12)

I also tried from UV room the command "Apply UV Set", but nothing changes.

So how can it happen, that the UV mesh in UV room is different to the UV map in Paint room and why is the command "Apply UV Set" not changing the result?

Just to answer the questions. Yes I did unwrap, yes I loaded the mesh when entering the Modelling room, yes I baked the mesh when leaving the Modelling room.

I tried many times to solve the problem, but no positive result. I tried to solve the manifold problem in many ways (within 3DCoat), but no positive result. 

It would be great if anyone could help me out.

Thank you very much for your assistance.

Best regards Walter

 

[Oleg Shapov]

22 hours ago, Stefka said:

It would be great if anyone could help me out.

Hello! Your model is so complex that it’s hard to immediately understand what’s going on. Could you share the scene to try to figure this out? Or maybe one of the more experienced 3D artists will answer soon.

[Stefka]

45 minutes ago, Oleg_Shapo said:

Your model is so complex that

Thank you for the response.

I know it is complex, but I think the complexity of the model is not the problem, but the manifold problem. The problem appears only in the area where the manifold problem was. As long as I was not trying to solve the manifold problem, I could change between the different rooms without problems. 

Thank you and best regards 

Walter

[digman]

I can only add suggestions or ask questions as this file would need to be looked at.  Read the tool tips on each function I mention.

Was this model created in 3DC using the modeling room or imported. 

If this model had a normal map and you just unwrapped in the uv room again, your normal map would be messed up which could cause a few problems in itself. You need to unwrap without rotation or flipping to preserve the normal map. Use PackUV2 for that function. if there is no normal map then you are fine. 

Did you use "Upd. Islands" under Commands after fixing your Manifold problem.  When you added new faces, they need new uv seam creation which I imagine you did, hence the use of Update islands, this confirms the new seams but no unwrapping is done. You had unwrapped before, so 3DC needs to know that you have altered the seams. Then you can unwrap again. Even though the new Uv seams are in the same location 3DC is not aware of them till you run the command.

I am not sure of the reason Apply UV is not functioning. I've not had that problem yet.

Since Apply UV set is not working, I would suggest deleting the model and paint layers in the paint room and re-baking.

Make sure all problems in the model are fixed. Unwrapping is correct. Bake to the paint room without a normal map to confirm everything is correct. If you need a normal map, you can rebake and 3DC will ask you if want to delete the model in the paint room before baking. Click on yes.

Also, I need to mention this: Normally when you edit a polygon mesh as you have done after baking those changes are not updated in the paint room. You must re-bake for the new edited mesh to be correct. You said that the mesh was being updated but that is generally not the case. 

Though the face or faces you deleted and the new faces are in the same location, re-baking is required. This could be part of your problem as well. 

Other than the above, I would need to look at the file. Pm me with a link to download the file if you wish. 

[Stefka]

Hi @digman

Thank you very much for your detailed answer. I will check and follow your proceedings as soon as possible and let you know the results.

Up to now thank you very much.

Best regards

Walter

[Stefka]

Hi @digman

First of all, I think I got it! Thank you sooooooooo much. I can´t thank you enough, because this solves a lot of problems for me.

To answer your question, the model was created in Sketchup 2017 and uploaded to 3DCoat.

My fault was, that I did the changes in the modeling room, than I baked with "Updated Painting Mesh with Retopo Mesh", so my model looked good in "Paint room". When I entered the "UV room", first of all I did not use "Upd. Islands" and then I used "Unwrap" instead of "PackUV2", this crashed my texture.

So the following may be interesting for some other users, this is my current and I hope correct sequence now.

In the "Modeling room", update the mesh by "Take mesh from the Painting room"

Do the model modifications.

Bake mesh by "Update Painting mesh with Retopo mesh", you may save it or not. (Up to you)

Change into "Paint room", model looks good.

Change into "UV room".

Press "Upd. Islands", then "PackUV2"

Change into "Paint room", model and texture is still fine.

Up to now I only did minor modifications in the "Modeling room", like deleting one or two faces, adding a seam or face here or changing soft seam to hard seam.

Dear @digman you deserve your title as "Reputable Contributor" and everyone who gets help from you can be happy!

Thank you again and best regards

Walter

PS: The problem of the different UV sets in UV room and Paint room came for sure from my misuse of the software.

The popup window of the command "PackUV2", for me was misleading. It says that it is just rearranging the islands, so I had no idea that the command would have anything to do with modifications on the model.

Just as an idea; wouldn´t it be great if you change your model in the "Modeling room" and when leaving and baking by "Update Painting mesh with Retopo mesh" that the UV islands are automatically updated and packed by PachUV2, so UV set in UV room and paint room are the same!? Just to make things simple.

[Stefka]

Hi @digman

Sorry to interrupt you again, but there is still an issue I´m having.

I did the editing of a defect model as described above and for the first turn, everything went well. This means I inserted the first face (triangle), followed all the steps as described above and got a perfect result, as you can see in "Picture1". Because there is also another face (triangle) missing, I went back to "Modeling room" and inserted another face (triangle), the semi transparent gray face. On the right side you can see the mesh, in the center is the lower part of the steering wheel, with the 2 holes where the spoke of the steering wheel is fixed. "Picture2"

If you hover with the mouse over the lower part of the steering wheel or over the spoke of the steering wheel, you can see on the right side the relevant meshes. (Picture3, Picture4)

Now I want to mark another seam. As soon as I click on "Mark Seam", the mesh of the 2 separated islands stick together, as you can see on the right side. I did not jet mark a seam. (picture5) Than I mark the seam.

Now I start the sequence with "Updated Painting Mesh with Retopo Mesh" and instantly as you can see by the semitransparent distortions, the texture is broken. (Picture6)

This does not change even if you follow the sequence to the end. The texture is broken. (Picture7)

So I´m very astonished that the sequence works fine for the first time, but does not work for the second time!?

I tried many ways to add the trriangle for the second time, by "R-Fill", by "Points to Polygons", by "Add/Splitt", but always the same result.

Do you have any idea what I did wrong?

Thank you very much for your assistance.

Best regards

Walter

PS: Astonishing to me  is the fact, that in (Picture5) you can see the combined mesh is intersecting the island of another object, but on this object the texture is not broken!?

 

Edited February 9 by Stefka

[digman]

I need to say without having the file in question I can only do so much as this is more technical and understanding how 3DCoat functions. Also, I cannot check the mesh for the problem area plus the area has very many polygons that are connected. If my solution fails it could the problem is in the mesh itself.

First: Model imported from Sketchup, if fixing problems in 3DCoat, I highly recommend not having any kind of normal map till all problems are fixed. If the model had no normal map things are easier. 

It appears you got color information you do not want to lose. You must be importing for per pixel painting and then fixing problems. You mentioned uploading but was not specific. Of course, when importing for Per Pixel painting a blank normal map is created but that is no problem as it has 0 depth normal information on it. You can check in the texture editor, selecting to show the normals. 

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Use Complex Checker to see what I mean below:

The UV islands have different orientations of U and V. (notice the letters are not in the same orientation) Not a problem till you have to create new uv seams after unwrapping but only happens at times depending on the new uv seam creation and UV island orientation.  It is not the fault of 3DC. 

The problem is the U and V orientation of the UV islands in question. 

When you update the UV islands, the orientation is not corrected so you get the stretching problem and overlapping problem.

I used the default creature as it shows your problem as well. My example is simpler but shows the problem. I deleted some seams and created new ones.

Two ways to fix this after updating UV islands:

1. Use regular Unwrap, this is where having no "normal map comes in". Of course, it unwraps all the islands again and might not be what you want.  

2. Manually fix the problem uv islands so you keep the same uv layout except those uv islands. 

First picture shows the UV orientation between the two UV Islands. The letters do not match the same orientation. 

Second picture just is highlighting the two UV islands. 

Third picture shows the stretching and overlapping that happens after running update uv islands. 

Fourth picture shows my manual fix.  

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Manual fixing is for when you do not want to unwrap the entire uv set again but fix the problem uv islands.

Create a new UV set:

Select and transfer the problem UV islands or UV island to the new uv set.

Regular unwrap these UV islands / UV island .Now they have more texture space of course but you can scale them down to the same texture space manually.

Select the uv islands and move them outside the 0 and 1 uv space. The reason is when you transfer them back to the original uv set they will not be overlaying any other islands. 

Select the UV islands and move them manually back into position Inside the 0 and 1 uv space.  You can rotate them as needed or scale them a little more if needed.

After you are done, delete unused UV sets.  Creating, Moving between UV sets and deleting unused ones are located in the top menu.

Next is to continue your workflow. 

Having problems between software applications when importing models is not uncommon at all. The main question is your 3D application able to solve many problems, not saying all problems. 3DCoat can solve many problems but understanding how to do so takes some time to learn and you are working on a more 

complex model.

EDIT. Also, even if the uv islands had the same orientation, location in UV space would be a factor too. If the uv islands are separated by UV location distance you would get stretching too. 

A lot to keep track of, is it not.  

I would suggest use the default Creature to practice on to better understand the process if my wording is not quite readable.

 

[digman]

This goes with my above post about your second problems

Why flip the U and V in UV islands or rotate uv islands anyway.

It creates a more logical UV workspace for texturing. Your uv islands line up in a way that painting across them is visually easier and more understandable. 

"""""""Now in 3DC we do not have to worry about that as we paint directly on the 3D model but what if we want to paint on the uv islands in the texture editor or paint on the uv set in an external editor.  The uv islands give you visual clues plus whole groups of uv islands can be arranged in a manner that is easier to understand what we are seeing. Also we just simply might like things tidy. """"""

In my simple example I have flipped the U and V plus rotated the UV islands so I can paint horizontally across them easily. You see the letters are in the same orientation and UV islands have been rotated correctly. You see the selected polygons are directly across from each other.  Imagine a uv set with a number of UV islands scattered around the uv space not having any flipping, rotating or creating groups plus rearranging, painting that kind of unorganized uv set in 2D would be a pain...  I just used these two UV islands too keep it very simple to understand. These are not all the uv islands in the set.

Now in some software I could sew these two uv islands together, but we have no sewing option in 3DC. 

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In your case you do not have to worry about the above except for problem fixing, it is just FYI and you might know this already.

[Stefka]

Hi @digman

Jesus Christ! You must have spent hours for the explanations! Thank you so much!

I will have to go through it and try to understand all the expert informations first.

I will come back to you as soon as possible.

But here are some additional informations regard your first paragraph.

The mesh from Sketchup has no colour informations or any UV map. I´m importing an OBJ file. On import to 3DCoat as you said, I´m using "Paint UV Mapped Mesh (Per Pixel)".

When importing I generate UV map by "Auto Mapping" option.

After checking the mesh in 3DCoat, I start painting. But sometimes there are still problems that I did not find in the first check. So now I have spent many hours in painting the model and there are 2 faces missing, f.e. One way would be to repair original model in Sketchup and reimport and restart painting, other way is to try to solve the problems in "Modeling room". For me it seams reasonable that the repair in "Modeling room" should be posssible and much faster. 

I for sure will go through your explanations in detail and I´m sure I will learn a lot about 3DCoat, but the point you did not handle was the fact, that on the first run, adding the first face, everything worked perfect, even so the face also connected the spoke and the steering wheel. (I think it was the face right to the missing face) Only in second turn when I added another face, attached to the first one, right beside of the first one, the things went wrong and the colour informations were broken. On that point, when second turn started, it can´t have anything to do with the original model, it can´t have to do anything with orientation of the different faces, a.s.o., because everything went well in the first turn, with exactly all the same facts. 

Please do not misunderstand my argumentation. For sure you are MUCH MORE experienced than I ever will be, but to me it makes no sense, that things went well on first turn but not on second turn if everything is exactly the same.

I´m sorry, I can´t send you the original broken file, because I already did some modifications and I have overwritten the old version.

Thank you so far for your excellent explanations!

Bets regards

Walter

[digman]

No problem at all, Texting and reading information and not understanding on my part or yours happens quite often with just using written words even with pictures included.

I agree if all at possible fix problems in Sketchup. even then a few errors might so the still need to know how to fix them in 3DC is important and which you are working through.

Side note:

I noticed in the pictures it appears that you have random sharp edges, the blue highlighted edges. in the future something to know is, when importing a model into the paint room 3DC will reorder your normals. Use lock normals on import to bring in the model as it was created in Sketchup.  You in Sketchup could have created a model with both sharp edges and smooth. You do not want 3DC to reorder the normals. I am only making a guess that these are random hard edges and not intentional ones, but I could be wrong. 

an example of using sharp edges is you when you want part of the model to be smooth and another part to stay sharp. The smoothing routine will not affect the sharp edges. 

Back to the topic. 

You have a sharp edge connecting to the star configuration. It splits the normals, if not needed remove the sharp edge and it could be part of the problem. 

I cannot tell you why the problem you described is happening without having the 3DC file which you cannot share. 

I would also fix both triangles at the same time before using your workflow to make sure no errors popup or to fix them. That is if I read right. You fixed one triangle, worked through your routine and then worked on the other triangle.

Suggestion:

If the problem is not easily solved, I would isolate the problem area to another uv set to help figure out the problem and work through solutions. That is what I would personally do. Also checking the orignal uv set is not being messed up when trying various solutions. 

Sometimes I will just get rid of a few polygons and remodel that area back in if all else fails to see if that fixes my problem. 

Hope all goes well and of course I will still answer questions as I have time do too so.

 

 

 

[Stefka]

Hi @digman

Regarding your side note: In Sketchup I can add sharp and smooth edges and they are imported correctly to 3DCoat. So this is intentionaly.

I clearly understand that giving the right answer is not possible without the model itself. I highly appreciate your suggestions.

But I think one of your "suggestions" brought the solution for my problem.

I isolated the defective part to a new UV set and followed all the seuqences as described above. The effect was, that only the defective part was influenced by any further problems like texture distortion and no other parts. 

I don´t know why I didn´t find the solution by myself, because I often split the UV set to different UV sets and recombine them in the end. So I´m aware of the process. But sometimes it needs a kick from an expert of find the solution.

I´m also thankful for all your extra explanations on the UV set. For sure this will be very helpful for me in the future.

Thank you again and I hope I can come back to you when I run into another problem.

Thank you and have a nice time.

Best regards

Walter

[digman]

Alright, it is always good when a problem or problems are solved, and that knowledge goes into your Kitbag. 

For sure I will answer any future questions you may have.