Shrinkwrap modifier of target curve is ignored when using the Curve modifier #51603

New Issue

s12a · 2017-05-24T00:25:38+02:00

s12a commented

2017-05-24 00:25:38 +02:00

System Information
Intel i5 3550
AMD Radeon RX480 4GB (Radeon Software 17.5.2)
Windows 10 64bit

Blender Version
Broken: 2.78.5 3bf69b2, 2.78c official

Short description of error
When using the Curve modifier on a mesh, the mesh will only deform along the base geometry of the target curve and will not take into account whether the curve is being deformed with some modifier like Shrink Wrap.

Exact steps for others to reproduce the error
I have attached a .blend file where this issue can be quickly observed.

shrink-wrap-bug.blend

Toggle the visibility of the Shrinkwrap modifier of the target curve on and off.
The mesh deformed with the Curve modifier will not change.

**System Information** Intel i5 3550 AMD Radeon RX480 4GB (Radeon Software 17.5.2) Windows 10 64bit **Blender Version** Broken: 2.78.5 3bf69b2, 2.78c official **Short description of error** When using the Curve modifier on a mesh, the mesh will only deform along the base geometry of the target curve and will not take into account whether the curve is being deformed with some modifier like Shrink Wrap. **Exact steps for others to reproduce the error** I have attached a .blend file where this issue can be quickly observed. [shrink-wrap-bug.blend](https://archive.blender.org/developer/F607463/shrink-wrap-bug.blend) 1) Toggle the visibility of the Shrinkwrap modifier of the target curve on and off. 2) The mesh deformed with the Curve modifier will not change.

s12a commented

2017-05-24 00:25:38 +02:00

Changed status to: 'Open'

s12a commented

2017-05-24 00:25:38 +02:00

Added subscriber: @s12a

perfection cat commented

2017-05-25 02:31:30 +02:00

Added subscriber: @sindra1961

perfection cat commented

2017-05-25 02:31:30 +02:00

If you use project mode in Shrinkwrap modifier, I think that you have to appoint axis.

s12a commented

2017-05-25 09:23:26 +02:00

The results are the same regardless of the Shrinkwrap modifier mode. The curve with the shrink wrap gets shrinkwrapped, but the objects that deforms along this curve doesn't follow its shrinkwrap deformation.

mathieu menuet commented

2017-05-25 09:58:12 +02:00

Added subscriber: @bliblubli

mathieu menuet commented

2017-05-25 09:58:12 +02:00

I think it's more a design problem than a bug. It's one of the area in Blender that doesn't follow the philosophy of "don't think for the user". The depsgraph will decide in which order the modifiers should be applied and sometime fails at finding the right order, because in some case their are several possibilities, all valid and it's more a question of artistic decision.
The solution to it would be to have a way for the user to order modifier execution. The everything node system will solve it on the long term. In the meantime, it could be solved with a scene stack of modifiers instead of being limited to object stack.

I think it's more a design problem than a bug. It's one of the area in Blender that doesn't follow the philosophy of "don't think for the user". The depsgraph will decide in which order the modifiers should be applied and sometime fails at finding the right order, because in some case their are several possibilities, all valid and it's more a question of artistic decision. The solution to it would be to have a way for the user to order modifier execution. The everything node system will solve it on the long term. In the meantime, it could be solved with a scene stack of modifiers instead of being limited to object stack.

s12a commented

2017-05-25 10:10:45 +02:00

From an end-user standpoint I would expect the object to curve along the visible (final/deformed) curve rather than its base geometry. If that was unwanted I could still duplicate the curve and remove the shrinkwrap modifier. With the current behavior I am prevented from choosing a possible option.

Sergey Sharybin commented

2017-05-29 15:47:18 +02:00

Added subscriber: @Sergey

Sergey Sharybin commented

2017-05-29 15:47:18 +02:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2017-05-29 15:47:18 +02:00

Sergey Sharybin self-assigned this 2017-05-29 15:47:18 +02:00

Sergey Sharybin commented

2017-05-29 15:47:18 +02:00

This is not about depsgraph, it is about some internal conventions which depsgraph have nothing to do about.

Basically, curve can be deformed in two different ways: one of them is to deform control points (bezier point and handles in this case) and tessellated points. Depending on what is your intention you use one or other one.

Then, when curve is used as a target for such things as "Follow Path" constraint, curve deform and some other, the so-called "Path" of curve is used. The path is a spline which is calculated at a state of pre-tessellated curve. This is because it's not possible to calculate it reliably from post-tessellated curve.

In your case, the first ever modifier (shirkwrap) is applied on tessellated curve, which leaves Path used for curve deform unaffected by the modifier.

While it is confusing, this is just how things work and changing this is not really a subject of bug tracker.. Thanks for the report anyway!

This is not about depsgraph, it is about some internal conventions which depsgraph have nothing to do about. Basically, curve can be deformed in two different ways: one of them is to deform control points (bezier point and handles in this case) and tessellated points. Depending on what is your intention you use one or other one. Then, when curve is used as a target for such things as "Follow Path" constraint, curve deform and some other, the so-called "Path" of curve is used. The path is a spline which is calculated at a state of pre-tessellated curve. This is because it's not possible to calculate it reliably from post-tessellated curve. In your case, the first ever modifier (shirkwrap) is applied on tessellated curve, which leaves Path used for curve deform unaffected by the modifier. While it is confusing, this is just how things work and changing this is not really a subject of bug tracker.. Thanks for the report anyway!

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Shrinkwrap modifier of target curve is ignored when using the Curve modifier #51603