Hooks no longer working if some parts of the mesh are removed #48290

New Issue

Dalai Felinto · 2016-04-27T15:20:55+02:00

Dalai Felinto commented

2016-04-27 15:20:55 +02:00

System Information
Windows

Blender Version
Broken: 2.77

Short description of error
Hooks no longer work properly if I remove vertices created before the hooked vertices

Exact steps to reproduce the error
Open: hook-remove.blend

enter edit mode
delete selected vertices
leave edit mode
:(

How to reproduce from scratch
(aka, how to re-create the sample file)

open default blender scene
edit cube and add a new cube in the same mesh
select a few vertices of the new cube and add a hook (Ctrl+H)
move the empty driven the vertices (in object mode, naturally)
now reproduce the "Exact steps to reproduce the error" instructions

**System Information** Windows **Blender Version** Broken: 2.77 **Short description of error** Hooks no longer work properly if I remove vertices created before the hooked vertices **Exact steps to reproduce the error** Open: [hook-remove.blend](https://archive.blender.org/developer/F307279/hook-remove.blend) * enter edit mode * delete selected vertices * leave edit mode * :( **How to reproduce from scratch** (aka, how to re-create the sample file) * open default blender scene * edit cube and add a new cube in the same mesh * select a few vertices of the new cube and add a hook (Ctrl+H) * move the empty driven the vertices (in object mode, naturally) * now reproduce the "Exact steps to reproduce the error" instructions

Dalai Felinto commented

2016-04-27 15:20:55 +02:00

Changed status to: 'Open'

Dalai Felinto commented

2016-04-27 15:20:55 +02:00

Added subscriber: @dfelinto

Philipp Oeser commented

2016-04-27 21:09:53 +02:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2016-04-27 21:09:53 +02:00

My findings after a quick glance at the code (will investigate more, too):
The hook modifier stores vertex indices from the original mesh to determine what to effect, so when these change (which they do when some vertices are deleted), the modifier will act on different vertices :/
But here is a nice workaround [that is somewhat hidden to be honest]:
(1) assign the desired hook-vertices to a vertexgroup
(2) deselect all vertices
(3) select the vertexgroup created in (1), making it active
(4) add the hook

the hook modifier will now have a vertex group already assigned (its basically a shortcut for a hook on all vertices limited to the vertexgroup)
this way you can delete vertices as you wish and the hook stays intact :)
not sure if this helps -- will also look more into the modifier to see if the original problem can be solved better...

My findings after a quick glance at the code (will investigate more, too): The hook modifier stores vertex *indices* from the original mesh to determine what to effect, so when these change (which they do when some vertices are deleted), the modifier will act on different vertices :/ But here is a nice workaround [that is somewhat hidden to be honest]: (1) assign the desired hook-vertices to a vertexgroup (2) **deselect** all vertices (3) select the vertexgroup created in (1), making it active (4) add the hook the hook modifier will now have a vertex group already assigned (its basically a shortcut for a hook on _all_ vertices limited to the vertexgroup) this way you can delete vertices as you wish and the hook stays intact :) not sure if this helps -- will also look more into the modifier to see if the original problem can be solved better...

Dalai Felinto commented

2016-04-27 21:22:09 +02:00

That's an interering workaround, and it seems to work fine. Thanks @lichtwerk

Gwenael Le Page commented

2016-04-28 11:07:31 +02:00

Added subscriber: @gwentiv

Gwenael Le Page commented

2016-04-28 11:07:31 +02:00

Confirmed on 2.77a linux. It seems to work exactly like Philipp said.
I wonder what the solution is (I mean, to avoid using Vgroups).
I suppose each vertex has an ID (I guess it is the index used by the Build modifier for instance...)

So either the vertices need to be re-ordered so that the indices of the vertices concerned by the hook bindings are the same. But that won't work if you suppress more vertices whose indices are below the ones tied to a hook than you have vertices free ABOVE that index...

So the hooks tied to a particular mesh must be updated with new, updated sets of indices. Is that a difficult task ?

Confirmed on 2.77a linux. It seems to work exactly like Philipp said. I wonder what the solution is (I mean, to avoid using Vgroups). I suppose each vertex has an ID (I guess it is the index used by the Build modifier for instance...) So either the vertices need to be re-ordered so that the indices of the vertices concerned by the hook bindings are the same. But that won't work if you suppress more vertices whose indices are below the ones tied to a hook than you have vertices free ABOVE that index... So the hooks tied to a particular mesh must be updated with new, updated sets of indices. Is that a difficult task ?

Philipp Oeser commented

2016-04-28 11:51:47 +02:00

I could image it working on a pointer list instead of a index list, but that would need some further investigation (will do when time permits -- propably not before weekend though...)

Campbell Barton commented

2016-04-29 09:35:46 +02:00

Added subscriber: @ideasman42

Campbell Barton commented

2016-04-29 09:35:46 +02:00

This can be supported by ensuring CD_SHAPE_KEYINDEX is added when there are hooks or vertex parents present.

Looked into this but would rather not do this in BM_mesh_bm_from_me which runs from modifiers.
This could run from ED_object_editmode_enter instead.

This can be supported by ensuring `CD_SHAPE_KEYINDEX` is added when there are hooks or vertex parents present. Looked into this but would rather not do this in `BM_mesh_bm_from_me` which runs from modifiers. This could run from `ED_object_editmode_enter` instead.

Campbell Barton was assigned by Bastien Montagne

2016-04-29 11:50:31 +02:00

Bastien Montagne commented

2016-04-29 11:50:31 +02:00

Added subscriber: @mont29

blender-admin commented

2016-04-29 15:39:50 +02:00

This issue was referenced by 6d0cae56e8

This issue was referenced by 6d0cae56e84306ed64a51005c4fb1811a40822b7

Campbell Barton commented

2016-04-29 15:42:18 +02:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue

2016-04-29 15:42:18 +02:00

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Hooks no longer working if some parts of the mesh are removed #48290