Unable to create manual curve to mesh UV with spline parameter #93811

New Issue

michael campbell · 2021-12-07T12:47:14+01:00

michael campbell commented

2021-12-07 12:47:14 +01:00

System Information
Operating system: Windows-10-10.0.19042-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 472.12

Blender Version
Broken: version: 3.1.0 Alpha, branch: master, commit date: 2021-12-02 18:49, hash: 56ff954030
Worked: (newest version of Blender that worked as expected)

Below file is creating uv's from the curve length and profile and then outputting as a custom_UV attribute. There seems to be squashing happening at the beginning and end.

spline parameter fac bug.blend

**System Information** Operating system: Windows-10-10.0.19042-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 472.12 **Blender Version** Broken: version: 3.1.0 Alpha, branch: master, commit date: 2021-12-02 18:49, hash: `56ff954030` Worked: (newest version of Blender that worked as expected) Below file is creating uv's from the curve length and profile and then outputting as a custom_UV attribute. There seems to be squashing happening at the beginning and end. [spline parameter fac bug.blend](https://archive.blender.org/developer/F12704164/spline_parameter_fac_bug.blend) ![image.png](https://archive.blender.org/developer/F12704168/image.png)

michael campbell commented

2021-12-07 12:47:14 +01:00

Added subscriber: @3di

blender-admin commented

2021-12-07 12:47:14 +01:00

#103908 was marked as duplicate of this issue

blender-admin commented

2021-12-07 12:47:14 +01:00

#93503 was marked as duplicate of this issue

michael campbell commented

2021-12-07 13:06:33 +01:00

only seems to happen on cyclic curves.

Jacques Lucke commented

2021-12-07 14:39:06 +01:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2021-12-07 14:39:06 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Jacques Lucke commented

2021-12-07 14:39:06 +01:00

Looks like the Spline parameter node does not handle cyclic splines correctly. Note that a fix to the node will probably only work when you also change the domain of the group output to face-corner.

Hans Goudey commented

2021-12-07 14:54:07 +01:00

Added subscriber: @HooglyBoogly

Hans Goudey commented

2021-12-07 14:54:07 +01:00

Sadly it's not that simple, this is more of a fundamental limitation with the current design of curves. One that I hadn't run into before actually.
{F12704446 size=full}
Since attributes are stored on spline control points, this interpolation from almost 1 to 0 in the last point is inevitable.

Feels like we should design a way around this, but it is not a bug for now. I'm on the fence about known issue vs. archived, but I'll keep it around as a reminder about this.

Sadly it's not that simple, this is more of a fundamental limitation with the current design of curves. One that I hadn't run into before actually. {[F12704446](https://archive.blender.org/developer/F12704446/image.png) size=full} Since attributes are stored on spline control points, this interpolation from almost 1 to 0 in the last point is inevitable. Feels like we should design a way around this, but it is not a bug for now. I'm on the fence about known issue vs. archived, but I'll keep it around as a reminder about this.

Hans Goudey changed title from ~~incorrect attribute values when creating from spline parameter's fac~~ to Unable to create manual curve to mesh UV with spline parameter

2021-12-07 14:56:03 +01:00

Case Kubesh commented

2022-01-27 05:06:53 +01:00

Added subscriber: @Chase-Kubesh

Case Kubesh commented

2022-01-27 05:06:53 +01:00

For now, here's a workaround. A little hacky but thats life. You end up with duplicate verts at index 0 and 1 of the circle, as thats the only way to fix it for now {F12826647 size=full} ProperUVsHack.blend

For now, here's a workaround. A little hacky but thats life. You end up with duplicate verts at index 0 and 1 of the circle, as thats the only way to fix it for now {[F12826647](https://archive.blender.org/developer/F12826647/image.png) size=full} [ProperUVsHack.blend](https://archive.blender.org/developer/F12826650/ProperUVsHack.blend)

Garek commented

2022-02-01 17:23:08 +01:00

Added subscribers: @Sanctus, @Garek

(null) McNull commented

2022-02-08 19:24:14 +01:00

Added subscriber: @null

CybranM commented

2022-05-16 20:03:03 +02:00

Added subscriber: @IihT2cWA9xiP30BsYphz3EiEISNoScoe

Oliver Weingarten commented

2022-07-11 19:31:35 +02:00

Added subscriber: @owei

Oliver Weingarten commented

2022-07-11 19:31:35 +02:00

Hi there!
Any news on this? Would be a pity NOT to be able to use custom closed curves in Geometry Nodes.
I have to use Houdini instead to get proper UVs on a closed curve?
Thanks!

Cheers,
oliver

Hi there! Any news on this? Would be a pity NOT to be able to use custom closed curves in Geometry Nodes. I have to use Houdini instead to get proper UVs on a closed curve? Thanks! Cheers, oliver

Hans Goudey commented

2022-07-12 14:22:10 +02:00

This really needs some research and thought IMO.
One way to solve it that I would be interested in exploring is adding a choice of interpolation methods to the store named attribute and capture attribute nodes, AKA "attribute metadata". That would tell the node the attribute is meant to be used as a UV, so it should move it to the face corner domain (and somehow choose a proper value for the last corner??)

This really needs some research and thought IMO. One way to solve it that I would be interested in exploring is adding a choice of interpolation methods to the store named attribute and capture attribute nodes, AKA "attribute metadata". That would tell the node the attribute is meant to be used as a UV, so it should move it to the face corner domain (and somehow choose a proper value for the last corner??)

michael campbell commented

2022-07-12 14:58:25 +02:00

maybe until you come up with that you could just add a closed/open curve option to the curve nodes. So the circle node for example would have two points (an end and a start) in the same location.

michael campbell commented

2022-07-12 15:06:16 +02:00

or in the set spline cyclic node you could have an 'align first to last' checkbox?

michael campbell commented

2022-07-12 15:23:12 +02:00

@HooglyBoogly have you checked how the standard curve code does it?

Right is a standard curve, left is a geometry node curve. Maybe you could just copy what someone's already done in the standard curves?

@HooglyBoogly have you checked how the standard curve code does it? Right is a standard curve, left is a geometry node curve. Maybe you could just copy what someone's already done in the standard curves? ![image.png](https://archive.blender.org/developer/F13288805/image.png)

Hans Goudey commented

2022-07-20 00:55:37 +02:00

Thanks for the comparison. It's not a question of whether it's possible or how the code would work, it's a question of making the design consistent with elsewhere in geometry nodes and generic enough that we don't need to refactor it in a few months. For example, how would it choose which attributes to interpolate this way?

Iliya Katushenock commented

2022-07-20 01:07:01 +02:00

Added subscriber: @mod_moder

Iliya Katushenock commented

2022-07-20 01:07:01 +02:00

I think the simplest is the vertex domain for the edge
like Edge Corner
But this is a head-on decision that requires huge changes.

You can infer Face Corner with a length factor

You can design nodes that have a FieldContext with multiple values, so that the user himself implements the value mixing function to implemetd field on domain node group

There can be many options, if you want, on RCS you can write the most thoughtful and useful

I think the simplest is the vertex domain for the edge like Edge Corner But this is a head-on decision that requires huge changes. You can infer Face Corner with a length factor You can design nodes that have a FieldContext with multiple values, so that the user himself implements the value mixing function to implemetd field on domain node group There can be many options, if you want, on RCS you can write the most thoughtful and useful

michael campbell commented

2022-07-20 02:13:16 +02:00

@HooglyBoogly for the uv, you'd just use spline factor to set 1st point = uv 0, last point = uv 1. first and last point would be in the same location for closed curves, which would resolve the issue we have here of not being able to store two uv values on the same point which is leading to a non seamless UV. To my recollection this is how closed splines are able to provide uv's in H (they're not actually closed). Interpolation of the UV's is done in the shader if I understood you correctly, but could be done with a spline factor to get the value of a different attribute at an interpolated point in geometry nodes.

Tolkfan commented

2022-12-02 21:01:00 +01:00

Added subscriber: @Tolkfan

Ivan commented

2022-12-24 03:25:48 +01:00

Added subscriber: @Deviner

Iliya Katushenock commented

2023-01-16 10:10:29 +01:00

Added subscriber: @Leroy-Xie

Philipp Oeser removed the

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Unable to create manual curve to mesh UV with spline parameter #93811