Option to export with original UVs (no inner cuts) + adjustable outline seam allowance

[xfurryfucker2x]

Please consider adding:

An option to export without inner cuts inside UV islands
→ basically, to use the original UV map as-is, instead of the automatically generated unfolded map.
This would be useful when the user already defined their own seams and doesn’t want any additional auto-cuts inside the islands, and for making sewing patterns.

An optional “outline” or offset around each island (seam allowance)
→ for sewing patterns, it would be great to have a selectable seam allowance width (e.g. 3–10 mm) added automatically around each island’s outline during export.

If not possible, please tell where in the code the cut generation happens. I tried hard to vibecode it for few hours straight...

[addam]

Inner cuts are supposed to be only added when strictly necessary. If any less seams would be generated, the net wouldn't be flat and couldn't be printed on paper. If you believe that the model you are currently working with is handled incorrectly, please attach it here.

Are you working with a stretchable material, as suggested in #73 and #98?

(The code does not generate cuts anywhere. Instead, it starts with disconnected faces and tries to join them together as much as possible. This way makes it easy to prevent self-overlaps.)

There is no direct option to add outline around islands but you can easily fake it by choosing Tabs: None, Numbers: Outside. These generated numbers will effectively create a buffer around the outline, and their size can be customized by Tabs and Text Size.

[xfurryfucker2x]

Thanks for the question. Yes, I am working with stretchable material, specifically fabrics like minky. I think it would be very useful to have an option in the exporter to generate patterns without any additional cuts.

I tested the workaround using the “Seams to Sewing Pattern” addon. I created a flat model from 3d model uvmap for cloth simulation with sewing, then used the exporter, and it produced the expected result. Almost everything worked as intended, although a few faces were cut, which is a bit strange since the model was completely flat planes.

For reference, a similar tool that handles this workflow is plushify.net

[addam]

Wow, thank you for these links! The Seams to Sewing Pattern addon looks like the right tool to properly design and preview models from elastic materials.

I'll review it some more but I believe the issues related to elastic materials can be closed, and I'll direct users to that addon instead.

[xfurryfucker2x]

Unfortunately the Seams to Sewing Pattern addon is not a working alternative. According to its author the exporter does not work in newer Blender versions and in practice it fails even in any older ones too.

So I would like to ask directly if you plan to add proper support or an export mode specifically for elastic or stretchable materials in this addon or if we should assume it will not be implemented ?

[addam]

I believe that designing from fabric or foam is fundamentally different from paper modeling. I'm thinking of adding some basic support but I don't think it could ever work for materials that actually can stretch.

If the Seams to Sewing Pattern addon does not work in newer versions, I'd rather contact the original author and rewrite it.

[xfurryfucker2x]

The Seams to Sewing Pattern add-on hasn’t been actively developed for several years now.

I haven’t personally worked with foam, but I do make plushies from minky fabric and generating sewing patterns directly from UVs actually works perfectly in practice if you know what are you doing.

The key requirement, however, would be to give users full manual control over where cuts and seam lines are placed, rather than leaving that to the automatic unfolding algorithm.

[addam]

Ok, I'll try to explain how the algorithm works. Maybe there's something I didn't understand correctly about your idea.

It starts with separate faces and joins them together to form the net. In the start all edges are seams and all edges (that are not marked as seam) will be eventually tried for joining two islands. Once there are no more edges to be tried, the process completes with result A.

Now, if I tried to support elastic fabric, I could do it only in the last step because I don't know beforehand how the net will be formed. (If I knew, there would be no need for unfolding, I could just call the UV Unwrap operator.) Fixing in the last step only affects one or two faces, leaving a possibly asymmetric result B.

What I believe is the correct result is C but getting there requires actually taking a very different approach from the start, and that's why I believe Seams to Sewing Pattern is superior for this task. Note that real models are way more complex than this.

What I actually could do is allowing the result B when you call the Unfold operator. That would generate few seams around the model, and would assume the material can stretch somehow. Exporting the asymmetric net makes little sense but you could then generate the net using UV Unwrap and export it from there. This might generate meaningful sewing patterns with very little effort.

However, from what I know about making fabric toys, it is essential to choose the right seam lines to get the right shape. Generating the seams from my script could not possibly match your artistic intention. And that's also why I believe that the Quick Clothsim approach taken by Seams to Sewing Pattern is great.

[xfurryfucker2x]

If I understood correctly, due to the way the algorithm is built, it’s not possible to achieve an output identical to UV Unwrap (Angle Based) without major code modifications.
If that’s indeed the case, I’d like to suggest adding a option to the addon (or even creating a separate one?) that would rely entirely on the UV Unwrap method, while using the existing code responsible for nesting and PDF export from this addon.

“It is essential to choose the right seam lines to get the right shape. Generating the seams from my script could not possibly match your artistic intention.”

That’s exactly my point instead of using an algorithm to automatically determine seam positions, I’d prefer to let the user decide where to place them.
As I may have mentioned before, a UV map created from a 3D model with properly placed seams is basically the only thing needed to produce a correct plush pattern what can i proff if needed.

I also need to clarify the matter of the Seams to Sewing Pattern addon.
I rechecked the export function. I could only review it through the author’s YouTube videos, since the export feature didn’t work for me despite testing it in four Blender versions (2.8, 2.9, 2.93, and 4.5).
From what I can tell, the addon essentially does the same as bpy.ops.uv.export_layout(), exporting only to the .svg format, with the possible addition of a scale conversion between the 3D model and the exported layout.
As for Quick ClothSim, it’s simply an algorithm that converts a mesh for cloth simulation purposes.

I’m attaching a vibecoded version of the custom addon that demonstrates my idea.
Main features:
Exports UV layout to a PDF file (with a basic nesting system)
Applies the 3D model’s scale to the exported pattern
Allows adding a custom seam allowance
Supports pattern pieces larger than A4 paper size
addon.zip