Path animation and the new curves type #98494

New Issue

Hans Goudey · 2022-05-30T12:39:28+02:00

Hans Goudey commented

2022-05-30 12:39:28 +02:00

Eventually every use of BKE_where_on_path will have to be removed, since it isn't supported by the new curves type.
This task is just about the two constraints that use evaluated positions, tangents, and normals of the first curve at a specific factor.

The eventual idea is to use versioning to change all legacy curve objects to the new curves object type, so this will have to be addressed for that transition.
But the change can also make animation workflows more intuitive and consistent with other Blender design.

Path Animation Settings

In order to support the new curves object, the "Path Animation" settings from the legacy curve object will have to be moved to the contraints that support them, because the new curves data-block will not store those specific settings. Any animation on the curve's path animation settings should also be moved to the constraint.

It's not important to make the design for the constraint perfect, since the long term goal is to replace them with a node based system anyway. The path animation constraint will then need these new settings:

"Frames"
"Evaluation Time"
"Clamp"

After the change, the "Path Animation" panel wouldn't exist anymore.

Parenting

The new curves object should not support the special parenting behavior for the legacy curve object that uses the path animation settings instead of regular parenting. This behavior will have to be removed with versioning, replaced with a proper follow path constraint, as described above.

Open Questions

What happens when there is no evaluated curve
Previously the constraints used the original curve with some set of the deformation modifiers applied. That was often problematic because what looked like a curve visually in the viewport was actually a mesh, so the constraints wouldn't work. Now we have a more precise definition of the evaluated curves, which is different than before.

This is potentially problematic, because the changes suggested above could introduce regressions. I would suggest using the original curve without any modifiers applied in this case. This behavior is still slightly different, but it is simple and easy to predict, and doesn't involve keeping track of a "pre-tesselation point" in the middle of modifier/nodes evaluation, which is basically a non-starter for the new curves object.

Todo

Implement updates to sample curve node (the constraints need to use that internally) (#95443)
Update constraints to use the new evaluated curves data
- Follow path constraint
- Clamp To constraint
Move path animation settings to constraints/curve deform modifier
Remove special parenting behavior by adding follow path constraints in versioning

Eventually every use of `BKE_where_on_path` will have to be removed, since it isn't supported by the new curves type. This task is just about the two constraints that use evaluated positions, tangents, and normals of the first curve at a specific factor. The eventual idea is to use versioning to change all legacy curve objects to the new curves object type, so this will have to be addressed for that transition. But the change can also make animation workflows more intuitive and consistent with other Blender design. ### Path Animation Settings ![image](/attachments/ccb31acd-ff6a-445e-9f36-0d1bac222c15) In order to support the new curves object, the "Path Animation" settings from the legacy curve object will have to be moved to the contraints that support them, because the new curves data-block will not store those specific settings. Any animation on the curve's path animation settings should also be moved to the constraint. It's not important to make the design for the constraint perfect, since the long term goal is to replace them with a node based system anyway. The path animation constraint will then need these new settings: - "Frames" - "Evaluation Time" - "Clamp" After the change, the "Path Animation" panel wouldn't exist anymore. ### Parenting ![image](/attachments/64471c1a-5107-4f80-a00c-381188be8339) The new curves object should **not** support the special parenting behavior for the legacy curve object that uses the path animation settings instead of regular parenting. This behavior will have to be removed with versioning, replaced with a proper follow path constraint, as described above. ### Open Questions **What happens when there is no evaluated curve** Previously the constraints used the original curve with some set of the deformation modifiers applied. That was often problematic because what looked like a curve visually in the viewport was actually a mesh, so the constraints wouldn't work. Now we have a more precise definition of the evaluated curves, which is different than before. This is potentially problematic, because the changes suggested above could introduce regressions. I would suggest using the original curve *without any modifiers* applied in this case. This behavior is still slightly different, but it is simple and easy to predict, and doesn't involve keeping track of a "pre-tesselation point" in the middle of modifier/nodes evaluation, which is basically a non-starter for the new curves object. ### Todo ![image](/attachments/b4274047-fee1-4208-bbd1-6ed7d6459161) - [x] Implement updates to sample curve node (the constraints need to use that internally) (#95443) - [ ] Update constraints to use the new evaluated curves data - [ ] Follow path constraint - [ ] Clamp To constraint - [ ] Move path animation settings to constraints/curve deform modifier - [ ] Remove special parenting behavior by adding follow path constraints in versioning

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Hans Goudey commented

2022-05-30 12:39:28 +02:00

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

Hans Goudey commented

2022-05-30 12:39:28 +02:00

Added subscriber: @HooglyBoogly

blender-admin commented

2022-05-30 12:39:28 +02:00

#98489 was marked as duplicate of this issue

Hans Goudey changed title from ~~Update constraints to use the new curves object~~ to Curve path animation and update to new curves type

2022-05-30 12:42:11 +02:00

Hans Goudey changed title from ~~Curve path animation and update to new curves type~~ to Curve path animation and the new curves type

2022-05-30 12:42:34 +02:00

Hans Goudey changed title from ~~Curve path animation and the new curves type~~ to Path animation and the new curves type

2022-05-30 12:42:40 +02:00

Hans Goudey commented

2022-05-30 12:45:54 +02:00

Added subscribers: @Mets, @SimonThommes, @lichtwerk

Demeter Dzadik commented

2022-05-30 12:55:07 +02:00

"Path Animation" settings from the legacy curve object will have to be moved to the contraints that support them

Thank god! 🙏

The new curves object should not support the special parenting behavior for the legacy curve object that uses the path animation settings instead of regular parenting.

Thank god! 🎉

What happens when there is no evaluated curve
using the original curve without any modifiers applied

Not sure I understand this one, would this mean trying to constrain something to a curve whose spline has been deformed using deforming modifiers like Shrinkwrap, with "Apply on Spline"(use_apply_on_spline) enabled, wouldn't work? That would be sad! D:

> "Path Animation" settings from the legacy curve object will have to be moved to the contraints that support them Thank god! :pray: > The new curves object should not support the special parenting behavior for the legacy curve object that uses the path animation settings instead of regular parenting. Thank god! 🎉 > What happens when there is no evaluated curve > using the original curve without any modifiers applied Not sure I understand this one, would this mean trying to constrain something to a curve whose spline has been deformed using deforming modifiers like Shrinkwrap, with "Apply on Spline"(`use_apply_on_spline`) enabled, wouldn't work? That would be sad! D:

Hans Goudey commented

2022-05-30 13:53:18 +02:00

Not sure I understand this one, would this mean trying to constrain something to a curve whose spline has been deformed using deforming modifiers like Shrinkwrap, with "Apply on Spline"(use_apply_on_spline) enabled, wouldn't work? That would be sad! D:

I mean that it wouldn't work when object evaluation has replaced the curve with an evaluated mesh (i.e. "bevel" or "extrude" have been used). My guess is that's generally fine because these curves are usually just for animation, you don't want to see them in renders too.
Theoretically we could still try to guess which intermediate geometry to use from the target object, something that's still a curve type. But that sounds complicated, error prone, and generally not compatible with something more complicated than a modifier stack.

>Not sure I understand this one, would this mean trying to constrain something to a curve whose spline has been deformed using deforming modifiers like Shrinkwrap, with "Apply on Spline"(`use_apply_on_spline`) enabled, wouldn't work? That would be sad! D: I mean that it wouldn't work when object evaluation has replaced the curve with an evaluated mesh (i.e. "bevel" or "extrude" have been used). My guess is that's generally fine because these curves are usually just for animation, you don't want to see them in renders too. Theoretically we could still try to guess which intermediate geometry to use from the target object, something that's still a curve type. But that sounds complicated, error prone, and generally not compatible with something more complicated than a modifier stack.

Andy Cuccaro commented

2022-05-30 14:04:05 +02:00

Added subscriber: @AndyCuccaro

Demeter Dzadik commented

2022-05-30 15:32:36 +02:00

In #98494#1366562, @HooglyBoogly wrote:
I mean that it wouldn't work when object evaluation has replaced the curve with an evaluated mesh

Ah okay, so deforming modifiers that can work on curve points will still work, that's good!
If you need to convert your curve to mesh while still letting it function as a curve, I think you can just separate the mesh generation part into a separate object using GeoNodes, and keep your curve as a real curve. 👍 Seems like a good workflow from user perspective in the first place.

> In #98494#1366562, @HooglyBoogly wrote: > I mean that it wouldn't work when object evaluation has replaced the curve with an evaluated mesh Ah okay, so deforming modifiers that can work on curve points will still work, that's good! If you need to convert your curve to mesh while still letting it function as a curve, I think you can just separate the mesh generation part into a separate object using GeoNodes, and keep your curve as a real curve. 👍 Seems like a good workflow from user perspective in the first place.

Hans Goudey referenced this issue

2023-02-28 20:35:36 +01:00

Replace legacy curve code with new system #105253

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Path animation and the new curves type #98494

Path Animation Settings

Parenting

Open Questions

Todo