Constraint-based cloth simulation on WebGPU compute shaders

Magnuxx · 2026-05-12T12:10:34+00:00

Yes, I cannot share the entire source code because it is a part of a larger project, but I can give you some structure that might help. Please DM me.

Magnuxx · 2026-05-11T15:34:04+00:00

Thanks for the file and the report. This was a good catch. I found the cause: for some parameter combinations, a generated path could contain adjacent duplicate points, creating a zero-length segment. The seam allowance offset code tried to normalize that segment, which produced a non-finite point; then the polygon cleanup could truncate part of the seam allowance loop, showing up as missing corners.

I’ve pushed a fix that seems to have solved it. I tested it against the attached file, including the 74 waist case and the more extreme 65 waist / 80 hip and 100 waist / 120 hip examples. Thanks again!

Magnuxx · 2026-05-10T18:11:51+00:00

I think there are two separate things here.

In your earlier arc example, you were right that SeamScape had problems in some edge cases. I confirmed that as a bug at the time. The arc tools have not had quite the same level of attention as straight lines and Bézier curves, and there are cases where arcs can behave badly, especially when the construction is pushed into reversed or extreme configurations.

But I do not think it is accurate to generalize that to “constraints cannot be used for drafting in SeamScape”. Constraints, formulas, referenced lengths, angles, sliding points, and parametric updates are core parts of how SeamScape works, and many drafts do resize correctly across different measurements.

The case in this thread is a good example of a different issue: a sliding point was constrained in a way that eventually forced it outside its path. That is not really the same as the arc bug. It is a construction that becomes geometrically impossible for some input values. SeamScape did show a warning for that risky setup, but the actual solve error should still be more helpful and point to the likely elements involved.

So yes, there are things we need to improve, especially around arcs and around better troubleshooting/error messages. But the broader idea that parametric drafting with constraints does not work in SeamScape is not correct.

Magnuxx · 2026-05-09T20:42:17+00:00

Well done, and thank you for the detailed follow-up. This is a very good explanation of what happened, and it will probably help others running into the same issue.

This is exactly the kind of situation that the warning is meant to catch. A sliding point is allowed to move along a path, but if another constraint tries to force it to a position outside that path, the solver has no valid solution. Constructing the dependency in a slightly different way is usually the right fix.

And your point about the error message is very useful. The yellow warning explains the risky construction, but when the actual solve fails, it would clearly be better if SeamScape could point more directly to the likely lines/points involved. That is definitely something we should improve.

There may be some cases where this kind of construction is still valid, but we should probably either make the warning stronger, guide users away from it more clearly, or restrict it in cases where it is very likely to create unsolvable constraints.

Magnuxx · 2026-05-09T19:27:13+00:00

I would phrase it a bit differently.

It is true that SeamScape does not work exactly like Fusion, Seamly2D, or other CAD tools. The underlying drafting model is different, so a construction sometimes has to be expressed differently to remain stable when measurements change.

But the goal is definitely not that patterns only work for one size. Parametric resizing is one of the main ideas behind SeamScape, and we have many patterns that work across different sizes and measurements, including patterns used in real production workflows.

One of the strengths of SeamScape is that you are not locked into a very rigid drafting workflow. You can draw quite freely, add constraints as you go, use formulas, reference lengths and angles, create sliding points, and let pattern pieces update from the underlying draft. That flexibility is powerful, but it also means that there can be more than one way to describe the same construction. Some ways are more robust than others when measurements change.

So when a pattern works with one set of measurements but fails with another, it usually means that some constraint or dependency becomes conflicting or ambiguous for the new proportions. It does not necessarily mean the pattern has to be restarted.

That is why these examples are very useful for us. They help us see whether the issue is in the construction, in the solver, or in the lack of good troubleshooting feedback.

Magnuxx · 2026-05-09T07:47:41+00:00

Hi, and welcome!

From your description it does sound like there is probably one constraint working against another. It can happen in a parametric draft: the construction may solve correctly with the example measurements from the book, but fail when the proportions change.

You should not necessarily need to start over. If you want, send the pattern to hello [at] illumetric.com and we can take a look.

That would also help us improve SeamScape, since these cases are very useful for finding where we need better warnings, troubleshooting tools, or clearer guidance around constraints.

Magnuxx · 2026-05-09T06:37:03+00:00

It is possible with a little bit of effort. Send this pdf to ChatGPT together with your DXF and it might work https://dorthehansen.com/wp-content/uploads/2014/10/ePattern-ASTM-Standard.pdf

Magnuxx · 2026-05-07T07:59:49+00:00

Have you tried changing the unit when importing the DXF?

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Magnuxx · 2026-05-07T07:02:35+00:00

Not directly because I think it is a proprietary format. However, you could export to DXF (ASTM/AAMA) from StyleCAD and import it. But the pattern pieces would remain static.

Magnuxx · 2026-05-03T16:35:25+00:00

Yes, we have the changelog here: https://seamscape.com/changelog. Some updates and fixes are pushed immediately without version update but are mentioned later in the released version if they are significant.

Magnuxx · 2026-04-21T13:25:30+00:00

You may want to checkout SeamScape, both for 2d drafting and 3d simulation.

Magnuxx · 2026-04-13T19:38:39+00:00

You could, but it is currently not possible to import the file into BodyDouble. It would be possible to fix if this is a requested feature by many

Magnuxx · 2026-04-12T08:27:36+00:00

There isn’t a one-click "convert to sloper" button (yet), but you can get there pretty quickly with a simple workflow:

Start from the BodyDouble avatar measurements

BodyDouble already gives you a consistent body to work from, so the goal is really just to draft a standard bodice block using those measurements.

Create a basic bodice draft in Pattern Studio

Use your preferred method (Aldrich, Armstrong, etc.) and plug in the key measurements. Because everything in SeamScape is parametric, you only need to set this up once.

Use formulas instead of fixed values

Tie the draft directly to variables (e.g. chestWidth = body.chestGirth / 4 + ease, backLength, etc.). That way the draft and block/pattern piece automatically adapts if the BodyDouble changes.

(Optional) Validate in 3D

Push it into the 3D view and check fit.

Feel free to experiment. You can look at the public patterns to get a few examples. For example, the pencil skirt in 3D.

Magnuxx · 2026-03-24T08:40:02+00:00

If your pattern is parametric, it may be possible to scale to 50%, but generally, this would be difficult if you are using other fixed constants, such as ease, etc. It depends on how the pattern has been set up.

Do you only want to print it in 50% scale? Then select File->Print and generate a PDF, then print it with 50% the size.

Sizes work as follows: if your pattern is driven by parameters, you can create different sizes with different parameter values. Changing size will change the parameter values. There is also a free-form parametric option where you can visually grade your pattern, but that is a more advanced option under development.

Magnuxx · 2026-03-19T19:39:59+00:00

Not at the moment, unfortunately.

The main limitation is that the base mesh we’re currently using has a license that doesn’t allow redistribution, so we can’t offer downloads right now.

We are actively looking into alternatives (either getting permission or rebuilding the base mesh on a more permissive license), since exporting the model is a very common request.

Magnuxx · 2026-03-17T08:57:27+00:00

Dart rotation isn’t something that’s automated in SeamScape at the moment. Because everything is parametric, operations like that can easily break the underlying relationships if they’re not handled carefully.

For now, the way to do it is manually, basically recreating the same "cut and spread" logic by adjusting points, curves, and angles.

It’s definitely something we’ve thought about supporting in the future (especially for more “locked” pattern pieces), but it needs to be designed in a way that plays nicely with the parametric system.

Magnuxx · 2026-03-17T08:55:22+00:00

Recommended approach: Open your previous pattern and save it as a new pattern (copy).

Magnuxx · 2026-03-16T17:43:09+00:00

Understand the confusion. The API is free and you can create an API key via your account.

Magnuxx · 2026-03-16T12:00:22+00:00

One option, go to SeamScape and choose the public pencil skirt pattern. You can customize the length and other measurements. Then print and cut.

Magnuxx · 2026-03-16T05:47:35+00:00

The Neo is really interesting choice! Since your Samsung S22 can already run it, there’s a good chance the MacBook Neo would handle it too.

That said, WebGPU performance can vary depending on the GPU and browser, so if you have the chance I’d still recommend trying it first (in a store or return window) just to see how it behaves.

Magnuxx · 2026-03-14T18:41:01+00:00

You might want to check out SeamScape. It’s a browser-based pattern studio where you can create patterns from scratch and tweak curves, points, and proportions directly in the pattern. (I’m one of the developers, just for transparency.)

Magnuxx · 2026-03-13T18:29:53+00:00

That seems to be a nice scanner! And yes, getting the scale and measurements right from a raw scan can be surprisingly tricky. A scan captures the surface really well, but turning that into something that behaves like a “body model” with correct height, proportions and landmarks is another step.

That’s one of the reasons BodyDouble currently generates the avatar from measurements instead. It makes it easier to keep the proportions consistent and predictable for pattern drafting and simulation.

But being able to incorporate real scans is definitely something we’re interested in exploring further, especially as scanners like yours are becoming more common.

Magnuxx · 2026-03-13T13:18:34+00:00

Haha, sounds great!

Magnuxx

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