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Remaining issues with hair curves #125700

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opened 2024-07-31 11:35:21 +02:00 by Simon Thommes · 4 comments
Simon Thommes commented 2024-07-31 11:35:21 +02:00
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With the new curves type attempting to replace the particle hair system there are a number of issues left that keep us from retiring the legacy system in favor of the new one. These issues are mainly, but not exclusively related to dynamics/animation.
This list is an attempt to bring them all in one task to keep track of them in one view to assess the required effort and see the progress towards that goal.

Notes:

  • This is all besides making the new curves type ready to replace the legacy curves for other use-cases than hair, which also still needs to fill a number of gaps. (#68981, #105253)
  • This is also besides the need for a builtin solution for hair simulation which is a hard requirement to replace the legacy system.

Disclaimer:
At this point the list is not necessarily complete!

Problems that are left:

  • Various workarounds left in node setups because of missing node features
    • merge by distance needs Group ID
    • sample nearest Curve
  • Convenience Features
    • surface geometry fallback
    • default UVmap fallback
    • presets/operators to manage operation order and modifier settings for correct deformation (currently the modular approach makes it non-trivial to avoid jittering hair during animation, which is a commonly reported issue)
    • dynamic node-group/modifier UI based on inputs (hide panels by boolean/enum)
  • replace blackbox Guide Interpolation with node-group
    • lists for multiple guide associations
  • replace blackbox Surface Deform with node-group
  • Surface Attribute Interpolation
    • generate+interpolate creates redundancy and collision, sincegenerate already samples the surface attributes and stores them per guide. Interpolate interpolates the existing attributes between guides, rather than using the ones sampled on the surface points.
  • User Confusion/Problems with modifier order for stable animation
  • UV smoothing under Subdivision creating discrepancy/invalid curves
  • Rest position attribute yielding inaccuracy with Subdivision
    • Interpolation settings per attribute
  • Curve Deformation lacking option to use guide deformation (e.g. clump tips)
With the new curves type attempting to replace the particle hair system there are a number of issues left that keep us from retiring the legacy system in favor of the new one. These issues are mainly, but not exclusively related to dynamics/animation. This list is an attempt to bring them all in one task to keep track of them in one view to assess the required effort and see the progress towards that goal. Notes: - This is all besides making the new curves type ready to replace the legacy curves for other use-cases than hair, which also still needs to fill a number of gaps. (#68981, #105253) - This is also besides the need for a builtin solution for hair simulation which is a hard requirement to replace the legacy system. Disclaimer: At this point the list is not necessarily complete! ### Problems that are left: - [ ] Various workarounds left in node setups because of missing node features - [ ] merge by distance needs Group ID - [ ] sample nearest Curve - [ ] Convenience Features - [ ] surface geometry fallback - [ ] default UVmap fallback - [ ] presets/operators to manage operation order and modifier settings for correct deformation (currently the modular approach makes it non-trivial to avoid jittering hair during animation, which is a commonly reported issue) - [ ] dynamic node-group/modifier UI based on inputs (hide panels by boolean/enum) - [ ] replace blackbox Guide Interpolation with node-group - [ ] lists for multiple guide associations - [ ] replace blackbox Surface Deform with node-group - [ ] [Discontinuity in geonode hair/fur when surface mesh is under deformation due to lack of tangent interpolation](https://projects.blender.org/blender/blender/issues/128184) - [ ] default surface tangent space - [ ] [Surface Attribute Interpolation](https://projects.blender.org/blender/blender/issues/122878) - [ ] generate+interpolate creates redundancy and collision, sincegenerate already samples the surface attributes and stores them per guide. Interpolate interpolates the existing attributes between guides, rather than using the ones sampled on the surface points. - [ ] [User Confusion/Problems with modifier order for stable animation](https://projects.blender.org/blender/blender/issues/109285) - [ ] UV smoothing under Subdivision creating discrepancy/invalid curves - [ ] Rest position attribute yielding inaccuracy with Subdivision - [ ] Interpolation settings per attribute - [ ] Curve Deformation lacking option to use guide deformation (e.g. clump tips)
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Simon Thommes added the
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Simon Thommes added this to the Nodes & Physics project 2024-07-31 11:35:22 +02:00
Ducktor commented 2024-09-26 00:59:30 +02:00
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default surface tangent space

Is this referring to how the surface deform node doesn't interpolate tangents across the surface of the mesh, leading to discontinuity in stuff like fur when the surface mesh is under deformation?

> default surface tangent space Is this referring to how the surface deform node doesn't interpolate tangents across the surface of the mesh, leading to discontinuity in stuff like fur when the surface mesh is under deformation?
Simon Thommes commented 2024-09-26 12:01:31 +02:00
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@Ducktor-Cid might be tangentially related, but this is more just about explicitly accessing mesh tangents in a way that they can be attached to a UV space to make sure they are stable.

Would be good if you could specifically report the issue you are referring to, so we can see if it's related to an existing one or track it separately and refer to it here in this task.

@Ducktor-Cid might be tangentially related, but this is more just about explicitly accessing mesh tangents in a way that they can be attached to a UV space to make sure they are stable. Would be good if you could specifically report the issue you are referring to, so we can see if it's related to an existing one or track it separately and refer to it here in this task.
Ducktor commented 2024-09-26 15:03:31 +02:00
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@SimonThommes Done. Issue can be found here: #128184

@SimonThommes Done. Issue can be found here: #128184
Simon Thommes commented 2024-09-26 15:24:30 +02:00
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Thanks, I added it to the list

Thanks, I added it to the list
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