UV triangle unwrap / flatten surface

Hi there,

Some time ago I made a piece of a prism turned towards the sky and now I want to make it in metal, so it had occurred to me to make a UV unwrap on the sides so that I had them flat, then vectorized them and sent them to a laser cutting machine for later mount them.

Prior to this, I was trying to do it with sheets of paper and I’m seeing that the sides don’t fit. Reading through the forums I have seen that for an unwrap to be a faithful flattening I have to do the step of “follow active quads” but this object that I made is made of triangles and when I perform the action of “tris to quads” it does not transform all of me the triangles.

If someone could help me I would be eternally grateful since I am very lost with the possible solutions.

Tris to quads (alt-J).

I tried but there are a few tris that do not convert into quads :frowning:

I don’t see how “follow the squads” will help you. In fact it will do the wrong thing: It forces straight lines, where (in your model) nothing straight should be!
grafik

The normal uv unwrap should do the trick in your case. it’s results in 4 simple chains of triangles (given that you marked all corner edges and the bottom as seam). How much is it wrong? Can you post a screenshot of your uv?

if that does not help, then perhaps the triangles are indeed problematic, because the are so strictly alternating. Then indeed making them into quads and dividing them in the middle may help to get better fitting flat sides.

Btw: you can visualize the streching in the overlay drop down:
grafik

There are some extra vertices in the bottom that doesn’t dissolve to quads. You have to do that manually.

Hi again, thanks for your responses and your time guys. I attach a picture of the unwrap

I am aware that in the base there are more vertices than optimal but I cannot convert some of the central part either. Also if you tell me that this is not the solution because it will turn everything into straight lines, what else could i do?

(Why the triangles might be problemtatic:)
if the unwrapping leads to totally unstreched uvs (all blue. for angle and length stretching) and it still does not work (Test that first!) it might be that a chain of triangles is not suitable for printing out / lasercutting:
The chains can be perfectly flatten. and -after printing and cutting- they should perfectly recreate the object. If you do all the folds!
grafik

If not, then the errors might accumulate and can lead to problems. My idea is to make it more stable by adding an loop cut in the side surfaces: so that the 3d structure of the surface is better approximated.


Still: only separate it into 3 parts. the middle line should stabelize the uv-unwrapping.

The form of the uv looks ok in principle. These white parts look suspicious, are where additional hidden faces?
grafik
Can you check with the stretching overlay, if there is some stretching (see my first post)?

I’m out for today.
happy blendering.

Hello @Tachtian ,

First of all, thank you very much for your interest in helping me! I really appreciate it.

I just tried what you told me and first of all here is a screenshot of the stretching:

It seems that everything is fine except for a localized triangle where you have suggested to me the problem of hidden additional faces. I have eliminated them but then the UV unwrap remains as follows:

However, these two vertices that in the unwrap are disconnected, in the three-dimensional piece it is united since if I only select one vertex and move it, both faces move. (Please tell me if I don’t explain myself well : '(

On the other hand, I will try to insert loop cuts on the sides even though the geometry is a bit weird.

If you can think of anything else that could help me or you think that after that stretch capture, the sides are perfectly flat and I’m the one who can’t make a proper paper mockup, tell me too hahaha

PD: As i can only post 1 picture per comment i attach the other one now:

Hello again,

I keep trying to solve the problem and I have seen when exporting the UV layer and viewing it with zoom in photoshop that there is a kind of deformation in the size of the polygons since these edges that I attach in the photo should fit perfectly and in the three-dimensional piece they do.

However, when it comes to unwrap there is something that is distorted

I’m glad to help. You can post a picture of the final masterpiece if you want to thank me :slight_smile:

These are just the projections from the left border onto the curved right border. I compared the actual length of the egdes: They seem to be fine.

Regarding the gap:

  • try to [M]erge > “by distance” to combine nearby vertices
  • If you use “smart unwrap” then try “Unwarp” instead and “UV” > “mark the 3 main edges as seam”. So that smart unwrap does not insert unexpected seams
  • If you already use “Unwrap”: is that edge marked as seam?

Good luck

I’m not sure if this helps but you could look at the following info:
https://docs.blender.org/manual/en/latest/addons/import_export/paper_model.html

It is possible that your geometry cannot be flattened accurately in to just 3 strips, the add on will not correct those problems.

To understand why the form may not be be flattened as you ideally want, you should do some reading on developable surfaces.

Typically a small amount of twist is possible, however, in looking at your form the rotation of the cross sections around the center axis may be too great, and you may need to recreate the form.

Can you share the file?

I might be able to offer some additional input if I can examine the geometry.