Interpolate curves is broken on curves objects if converted from particle system #118305

New Issue

SleepyEngi · 2024-02-15T02:29:22+01:00

SleepyEngi commented

2024-02-15 02:29:22 +01:00

System Information
Operating system: rtx 2060 super
Graphics card: windows 10

Blender Version
Broken: 3.6, 4.0.2
Worked:

Short description of error
Interpolate curves node group does not work on curves objects that were made from a particle system through the convert particle system to curves option. bald spots are generated, which do not appear if you make a new fur object.
Missing attributes don't matter, even after deleting all the attributes on the new object it still works, but not on the converted particle system

Exact steps for others to reproduce the error

Convert a particle system to curves, attach it to the surface, and set the uv map.
Use the geometry nodes to interpolate curves
Bald spots will appear. they are more apparent with smaller "Max neighbors" settings, but it does not fix the issue in larger objects. And changing this in a working regular fur object does nothing.

I tested having the same attributes on both objects and saw no difference. This happens in the "interpolate hair curves" node as well.

Edit 1:
Further testing, it seems it can happen on regular fur objects as well, if the density is high enough. Unclear what even causes this and why this issue only suddenly started appearing as I've worked with way higher densities before.

Edit 2:
Interestingly, in my mammoth model, the curves are not truly gone but appear in rendered mode or in renders. If you apply the modifier the curves are still there. If you delete a large amount of other "visible curves", they re-appear. However, if I increase the amount of curves even further, the truly disappearing curves issue occurs. In this case, the curves become "0-length" curves, and will not appear in rendered mode.

However, in the Suzanne model provided, this is not the case. If you apply the modifier, the curves instead become 0-length curves, and do not appear in rendered mode.

It seems this issue might actually be 2 different issues? One that is only visual in the viewport if too many curves are displayed, and one that actually breaks the interpolation if there's too many curves?

Edit 3:
The "additional subdivisions" setting in the viewport might be relevant. Setting it to 3 has a much lower ... "display limit" on the amount of curves, while setting it to 2 returns many of the missing curves to the viewport. This only applies to curves that only disappeared visually though, with the Suzanne file not benefitting from it.

**System Information** Operating system: rtx 2060 super Graphics card: windows 10 **Blender Version** Broken: 3.6, 4.0.2 Worked: **Short description of error** Interpolate curves node group does not work on curves objects that were made from a particle system through the convert particle system to curves option. bald spots are generated, which do not appear if you make a new fur object. Missing attributes don't matter, even after deleting all the attributes on the new object it still works, but not on the converted particle system **Exact steps for others to reproduce the error** 1. Convert a particle system to curves, attach it to the surface, and set the uv map. 2. Use the geometry nodes to interpolate curves 3. Bald spots will appear. they are more apparent with smaller "Max neighbors" settings, but it does not fix the issue in larger objects. And changing this in a working regular fur object does nothing. I tested having the same attributes on both objects and saw no difference. This happens in the "interpolate hair curves" node as well. **Edit 1:** Further testing, it seems it can happen on regular fur objects as well, if the density is high enough. Unclear what even causes this and why this issue only suddenly started appearing as I've worked with way higher densities before. **Edit 2:** Interestingly, in my mammoth model, the curves are not truly gone but appear in rendered mode or in renders. If you apply the modifier the curves are still there. If you delete a large amount of other "visible curves", they re-appear. However, if I increase the amount of curves even further, the truly disappearing curves issue occurs. In this case, the curves become "0-length" curves, and will not appear in rendered mode. However, in the Suzanne model provided, this is not the case. If you apply the modifier, the curves instead become 0-length curves, and do not appear in rendered mode. It seems this issue might actually be 2 different issues? One that is only visual in the viewport if too many curves are displayed, and one that actually breaks the interpolation if there's too many curves? **Edit 3:** The "additional subdivisions" setting in the viewport might be relevant. Setting it to 3 has a much lower ... "display limit" on the amount of curves, while setting it to 2 returns many of the missing curves to the viewport. This only applies to curves that only disappeared visually though, with the Suzanne file not benefitting from it.

Broken interpolate.PNG

428 KiB

Broken curves.PNG

556 KiB

Missing curves.blend

3.4 MiB

Working curves.PNG

595 KiB

SleepyEngi added the

labels 2024-02-15 02:29:23 +01:00

SleepyEngi commented

2024-02-15 03:55:51 +01:00

I'm very confused as to why this issue started happening, as I've definitely made curve objects with over 5 million splines and over 30 million control points but didn't experience this before. Been testing all day but no results on a cause. I went back to 3.6 to see if it happened- and yes, it does. But it didn't before. I have no idea what the difference might be.

Edit: It turns out this might be 2 separate issues, because the mammoth file and the Suzanne file seem to have different properties, where the mammoth file is only visual, but the curves are technically still there and appear in rendered mode or if you delete other curves almost like a visual limit on the amount of curves that can be displayed, while in the Suzanne file the curves are instead 0-length curves, and if applied they become just flat points.

I'm very confused as to why this issue started happening, as I've definitely made curve objects with over 5 million splines and over 30 million control points but didn't experience this before. Been testing all day but no results on a cause. I went back to 3.6 to see if it happened- and yes, it does. But it didn't before. I have no idea what the difference might be. Edit: It turns out this might be 2 separate issues, because the mammoth file and the Suzanne file seem to have different properties, where the mammoth file is only visual, but the curves are technically still there and appear in rendered mode or if you delete other curves almost like a visual limit on the amount of curves that can be displayed, while in the Suzanne file the curves are instead 0-length curves, and if applied they become just flat points.

Philipp Oeser commented

2024-02-15 10:12:21 +01:00

Can confirm, cannot make sense of it either.

Philipp Oeser added

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Interpolate curves is broken on curves objects if converted from particle system #118305