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Replace legacy curve code with new system #105253

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opened 2023-02-27 15:45:02 +01:00 by Dalai Felinto · 2 comments
Dalai Felinto commented 2023-02-27 15:45:02 +01:00
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Feature Replacement / Versioning

  • Edit mode
  • Remove or replace features
    • Shape keys
    • Vertex parenting
    • Hooks
    • Edit mode hiding
    • 2D curve UI distinction
    • Texture space
  • Remove features
    • Special tilt and radius interpolation
  • #96455
  • #98494
  • Replace "Offset" slider with node group
  • Replace "Taper Object" feature with node group
  • Replace implicit curve meshing with node group(s)
    • "Round" profile
      • All fill types
      • Extrude
      • Depth
    • Object profile
    • Custom profile (custom profile editor as node)
      • Extrude
      • Depth
    • "Start & End Mapping" (potentially not all modes)
  • Replace Spline Smooth flag with "sharp_face" attribute in versioning

Cleanup

  • Remove curves edit mode
  • Remove all references to OB_CURVES_LEGACY
  • Remove many references to CurveCache
  • Remove unused code

References

### Feature Replacement / Versioning - [ ] Edit mode - [x] #105053 - [x] #105055 - [ ] #105037 - [ ] #105038 - [ ] Separate selection to new object - [x] Duplicate operator - [ ] Mirror menu - [ ] Snap menu - [ ] #101778 - [ ] Set curve type - [ ] Set cyclic - [ ] Remove or replace features - [ ] Shape keys - [ ] Vertex parenting - [ ] Hooks - [ ] Edit mode hiding - [ ] 2D curve UI distinction - [ ] Texture space - [ ] Remove features - [ ] Special tilt and radius interpolation - [ ] #96455 - [ ] #98494 - [ ] Replace "Offset" slider with node group - [ ] Replace "Taper Object" feature with node group - [ ] Replace implicit curve meshing with node group(s) - [ ] "Round" profile - [ ] All fill types - [ ] Extrude - [ ] Depth - [ ] Object profile - [ ] Custom profile (custom profile editor as node) - [ ] Extrude - [ ] Depth - [ ] "Start & End Mapping" (potentially not all modes) - [ ] Replace Spline Smooth flag with "sharp_face" attribute in versioning ### Cleanup - [ ] Remove curves edit mode - [ ] Remove all references to `OB_CURVES_LEGACY` - [ ] Remove many references to `CurveCache` - [ ] Remove unused code ### References * #95355 * #68981
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Dalai Felinto added this to the 4.0 milestone 2023-02-27 15:45:02 +01:00
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Dalai Felinto added this to the Nodes & Physics project 2023-02-27 15:45:03 +01:00
Dalai Felinto changed title from Replace the old curves code with the new one to Replace the old curves code with the new one for 4.0 2023-02-27 15:45:33 +01:00
Hans Goudey changed title from Replace the old curves code with the new one for 4.0 to Replace legacy curve code with new system 2023-02-28 18:04:39 +01:00
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Tomas-Silvestre commented 2023-03-06 16:19:48 +01:00
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Does this also affect the text object?

Does this also affect the text object?
Hans Goudey removed this from the 4.0 milestone 2023-08-31 21:07:00 +02:00
Demeter Dzadik commented 2024-07-26 18:23:56 +02:00
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I'd like to thoroughly explain a fundamental limitation with rigging with curves, specifically about Twist, in hopes that it might give a chance for the new curve system to provide a solution.

Let's say you want to rig a dino's tail:

The standard setup: Object is deformed by a Curve Modifier, and the curve is deformed with bones via Hooks.
The curve and everything else is parented to the big bone in the middle, so rotating that works fine.
But the other bones just control curve points via Hook modifiers, and since those don't affect twist, you simply cannot twist only a part of this dino tail (such that the spikes point downwards).

Bad Solution 1: Try to drive the Tilt of the curve points with a bone transform.
Well, this works... Except, what space? With Local Space, it will fail as soon as the rotation is coming from a parent.
With Pose Space... Well, drivers don't have a Pose Space option, but we can convert their Local Space to Pose Space by using an Armature Constraint instead of parenting.

It's a step up, but flipping the bones upside down fails to flip the mesh upside down. I sort of understand why, but not well enough to explain it. And our tilt drivers don't help at all with this case. We can experiment with the different Twist Methods, and quickly find that none of them fix this issue.

Bad Solution 2: Just use Bendy Bones.
Bendy Bones don't struggle with twist and behave how one would expect. However, Bendy Bones deform meshes with the Armature Modifier, and that's not the same as curve deform; You can't shape the curvature of the deformation without squashing and stretching the bones.

And that's pretty much it. You just can't use curves to rig things that need to flip around or rotate a lot, because you'll run into issues with twist, no matter what you do. Sorry for the wall of text.

Here's the .blend file to play with: dino_tail.blend

Do you guys think this is a solvable problem for the new curve type?

I'd like to thoroughly explain a fundamental limitation with rigging with curves, specifically about **Twist**, in hopes that it might give a chance for the new curve system to provide a solution. Let's say you want to rig a dino's tail: <video src="/attachments/6d173ee1-b4f7-4aa7-b49c-663448c272f8" title="dino_tail_twist.mp4" controls></video> The standard setup: Object is deformed by a Curve Modifier, and the curve is deformed with bones via Hooks. The curve and everything else is parented to the big bone in the middle, so rotating that works fine. But the other bones just control curve points via Hook modifiers, and since those don't affect twist, you simply cannot twist only a part of this dino tail (such that the spikes point downwards). --- **Bad Solution 1**: Try to drive the Tilt of the curve points with a bone transform. Well, this works... Except, what space? [With Local Space, it will fail as soon as the rotation is coming from a parent.](/attachments/784e9eff-e4a9-4929-8a7e-1c0c743ad434) With Pose Space... Well, drivers don't have a Pose Space option, but we can [convert their Local Space to Pose Space by using an Armature Constraint instead of parenting.](/attachments/cd662f3d-2a7d-4e62-9923-5c2c3a01b45f) It's a step up, but flipping the bones upside down fails to flip the mesh upside down. I sort of understand why, but not well enough to explain it. And our tilt drivers don't help at all with this case. We can experiment with the different Twist Methods, and quickly find that none of them fix this issue. --- **Bad Solution 2**: Just use Bendy Bones. Bendy Bones don't struggle with twist and behave how one would expect. However, Bendy Bones deform meshes with the Armature Modifier, and that's not the same as curve deform; [You can't shape the curvature of the deformation without squashing and stretching the bones.](/attachments/a46eec6a-ac20-42fa-885a-1ebcfb9caa51) --- And that's pretty much it. You just can't use curves to rig things that need to flip around or rotate a lot, because you'll run into issues with twist, no matter what you do. Sorry for the wall of text. Here's the .blend file to play with: [dino_tail.blend](/attachments/0b730109-6acb-432a-a2c8-a30ba7147eb3) Do you guys think this is a solvable problem for the new curve type?
dino_tail_twist_driven_tilt_local_space.mp4
1.2 MiB
dino_tail_twist.mp4
2.2 MiB
dino_tail_twist_with_bendy_bones.mp4
2.4 MiB
dino_tail_twist_driven_tilt_pose_space.mp4
1.3 MiB
dino_tail.blend
967 KiB
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