Vertex Group Select/Deselect fails after mesh was extruded and vertex group was again assigned #53436

New Issue

ronan ducluzeau · 2017-11-30T23:58:15+01:00

(Deleted) commented

2017-11-30 23:58:15 +01:00

(Migrated from localhost:3001)

start with same blend project as used in https:*developer.blender.org/T53435
NOTE: this is a bug, not a suggestion as in the other task #53435.

Files : VertexGroupError.zip
VGerror0.jpg shows a mesh with a new vertex group "Group1" created.
VGerror1.jpg shows the same mesh after pressing "Deselect" that "Group1".
VGerror2.jpg shows it with manually added faces, which were also deselected due to
the fact, that they share vertices with vertex "Group1".
All these faces get assigned to vertex group "Group2".
VGerror3.jpg shows the situation, when now again "Deselect" of "Group2" was done.
Think of the entire mesh to be a human finger. "Group1" here would be the nail.
On deselecting all other faces (here in "Group2") the nail should be selected,
but due to the shared vertices, only a part of it is selected.
see VGerror4.jpg
VGerror5.jpg : extruding out face to left on bottom of the "finger".
VGerror6.jpg : select "Group2" now selects also the new vertices (which seems to be ok)
VGerror7.jpg : manually deselct the new extruded faces. and assign all selected to vertex group "Group2"
VGerror8.jpg : but pressing "select" on "Group2" still selects also the extruded ones!!! Bug!

WORKAROUND: replacing the current "Group2" with a new vertex group "Group3", but that's no practical solution for many situations.

                        cause then always the old vertex group "Group2" must be deleted and a new vertex group must be created and assigned. 
                        This is very bad in a project with many vertex groups

reproduce this issue by selecting "Group2" then deselect the vertices on left bottom,
then again press select "Group2"

Blender Version: 2.79 (but I think also same behaviour in older versions)

start with same blend project as used in [https:*developer.blender.org/T53435 ](https:*developer.blender.org/T53435) NOTE: this is a bug, not a suggestion as in the other task #53435. Files : [VertexGroupError.zip](https://archive.blender.org/developer/F1249035/VertexGroupError.zip) VGerror0.jpg shows a mesh with a new vertex group "Group1" created. VGerror1.jpg shows the same mesh after pressing "Deselect" that "Group1". VGerror2.jpg shows it with manually added faces, which were also deselected due to the fact, that they share vertices with vertex "Group1". All these faces get assigned to vertex group "Group2". VGerror3.jpg shows the situation, when now again "Deselect" of "Group2" was done. Think of the entire mesh to be a human finger. "Group1" here would be the nail. On deselecting all other faces (here in "Group2") the nail should be selected, but due to the shared vertices, only a part of it is selected. see VGerror4.jpg VGerror5.jpg : extruding out face to left on bottom of the "finger". VGerror6.jpg : select "Group2" now selects also the new vertices (which seems to be ok) VGerror7.jpg : manually deselct the new extruded faces. and assign all selected to vertex group "Group2" VGerror8.jpg : but pressing "select" on "Group2" still selects also the extruded ones!!! Bug! WORKAROUND: replacing the current "Group2" with a new vertex group "Group3", but that's no practical solution for many situations. ``` cause then always the old vertex group "Group2" must be deleted and a new vertex group must be created and assigned. This is very bad in a project with many vertex groups ``` reproduce this issue by selecting "Group2" then deselect the vertices on left bottom, then again press select "Group2" Blender Version: 2.79 (but I think also same behaviour in older versions)

(Deleted) commented

2017-11-30 23:58:15 +01:00

(Migrated from localhost:3001)

Changed status to: 'Open'

(Deleted) commented

2017-11-30 23:58:15 +01:00

(Migrated from localhost:3001)

Added subscriber: @(Deleted)

ronan ducluzeau commented

2017-12-01 16:32:06 +01:00

Added subscriber: @zeauro

ronan ducluzeau commented

2017-12-01 16:32:06 +01:00

As explained in manual, assignement is additive.
https://docs.blender.org/manual/en/dev/modeling/meshes/properties/vertex_groups/assigning_vertex_group.html#working-with-content-of-vertex-groups

You can create a vetex group by selecting and assigning vertices one by one. You don't have to re-select all vertices of the group to modify their assignement.
Result that you are expecting can be achieved by selecting extruding faces and pressing Remove button.

While its disputable how this should work, its behaving as intended and not an error in the code.
So, I am closing this report.

I don't really see a design issue, here. First goal of vertices groups is assignement to armature bones (not vertces selection for modeling purpose).
In this perspective, assignement of one vertex to multiple groups is needed to obtain smoothed weight painting.
For 2.8, there is already a proposal to create Face Maps. #51675

As explained in manual, assignement is additive. https://docs.blender.org/manual/en/dev/modeling/meshes/properties/vertex_groups/assigning_vertex_group.html#working-with-content-of-vertex-groups You can create a vetex group by selecting and assigning vertices one by one. You don't have to re-select all vertices of the group to modify their assignement. Result that you are expecting can be achieved by selecting extruding faces and pressing Remove button. While its disputable how this should work, its behaving as intended and not an error in the code. So, I am closing this report. I don't really see a design issue, here. First goal of vertices groups is assignement to armature bones (not vertces selection for modeling purpose). In this perspective, assignement of one vertex to multiple groups is needed to obtain smoothed weight painting. For 2.8, there is already a proposal to create Face Maps. #51675

ronan ducluzeau commented

2017-12-01 16:32:20 +01:00

Changed status from 'Open' to: 'Archived'

ronan ducluzeau closed this issue

2017-12-01 16:32:20 +01:00

ronan ducluzeau self-assigned this 2017-12-01 16:32:20 +01:00

(Deleted) commented

2017-12-02 01:36:53 +01:00

(Migrated from localhost:3001)

However, I think its wrong at all. The documentation states this invalid behaviour also, but when you assign something, then you directly set the current selection to only those, which are selected. "Adding" could be an other additional button for what the docs describe, but using the word "assign" for that is misleading

However, I think its wrong at all. The documentation states this invalid behaviour also, but when you **assign** something, then you directly set the current selection to only those, which are selected. "Adding" could be an other additional button for what the docs describe, but using the word "assign" for that is misleading

ronan ducluzeau commented

2017-12-02 09:38:08 +01:00

Changed status from 'Archived' to: 'Archived'

ronan ducluzeau commented

2017-12-02 09:38:08 +01:00

You are right if we are focusing only on the belonging to the vertex group.
But here, user is also assigning a weight value to vertices at same time.
https://en.wiktionary.org/wiki/assign

Replacing "Assign" by "Add" would be misleading for user who want to modify weight value.

From a pratical point of view, it is better to do both operations in one click instead of two.

Maybe there is a chance to find a less confusing term. It is still not a bug but a design issue.
So, I archive the design issue for UI team.

You are right if we are focusing only on the belonging to the vertex group. But here, user is also assigning a weight value to vertices at same time. https://en.wiktionary.org/wiki/assign Replacing "Assign" by "Add" would be misleading for user who want to modify weight value. From a pratical point of view, it is better to do both operations in one click instead of two. Maybe there is a chance to find a less confusing term. It is still not a bug but a design issue. So, I archive the design issue for UI team.

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Vertex Group Select/Deselect fails after mesh was extruded and vertex group was again assigned #53436