'Dissolve' operator leaves inconsistent selection #72806

New Issue

Stanislav Blinov · 2019-12-30T20:47:16+01:00

Stanislav Blinov commented

2019-12-30 20:47:16 +01:00

Blender Version
Broken: 2.82 (62d131e962) (down to, and including, 2.79)
Worked: N/A

Short description of error
After dissolution of edges in Edge selection mode, some vertices not connected with edges remain selected (which is indicated by a tool gizmo, Verts readout in the status bar, and verified by switching to Vertex selection mode).

Exact steps for others to reproduce the error

In a empty scene, add a mesh Grid.
Switch to edit mode and Edge selection mode.
Select one edge somewhere inside the grid (not on border).
Dissolve it via the Delete -> Dissolve Edges or a default shortcut Ctrl+X.
Verts readout in the status bar should show 2 selected vertices (despite you being in edge mode with no edges selected).
Switch to Vertex selection mode: the two verts from that dissolved edge are still selected.
Deselect all, switch to Edge selection mode and box-select one square at the corner of the Grid.
Dissolve edges as in (4).
Note that this time, Verts in status bar only shows one selected vertex: switching to Vertex mode would reveal it's the corner one.

It would seem that the vertices do remain "selected" for operators as well: after (4) or (8) you can transform those verts using a gizmo or shortcuts, extrude them (with strange results), connect them using Fill or Connect Vertex Path, and delete them (even though you're in Edge mode).

Update: Video demo here .

**Blender Version** Broken: 2.82 (62d131e962d6e0a4f39db98d4f89243c16c55779) (down to, and including, 2.79) Worked: N/A **Short description of error** After dissolution of edges in Edge selection mode, some vertices not connected with edges remain selected (which is indicated by a tool gizmo, Verts readout in the status bar, and verified by switching to Vertex selection mode). **Exact steps for others to reproduce the error** 1. In a empty scene, add a mesh Grid. 2. Switch to edit mode and Edge selection mode. 3. Select one edge somewhere inside the grid (not on border). 4. Dissolve it via the Delete -> Dissolve Edges or a default shortcut Ctrl+X. 5. Verts readout in the status bar should show 2 selected vertices (despite you being in edge mode with no edges selected). 6. Switch to Vertex selection mode: the two verts from that dissolved edge are still selected. 7. Deselect all, switch to Edge selection mode and box-select one square at the corner of the Grid. 8. Dissolve edges as in (4). 9. Note that this time, Verts in status bar only shows one selected vertex: switching to Vertex mode would reveal it's the corner one. It would seem that the vertices do remain "selected" for operators as well: after (4) or (8) you can transform those verts using a gizmo or shortcuts, extrude them (with strange results), connect them using Fill or Connect Vertex Path, and delete them (even though you're in Edge mode). Update: Video demo [here ](https://youtu.be/FAfhSU2AdbQ).

Stanislav Blinov commented

2019-12-30 20:47:16 +01:00

Added subscriber: @Stan_Pancakes

Germano Cavalcante commented

2020-01-08 18:58:17 +01:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-01-08 18:58:17 +01:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Germano Cavalcante commented

2020-01-08 18:58:17 +01:00

By "box-select one square at the corner of the Grid" you mean this?:

In this case the vertices of the selected edges will also be deleted, so they will not appear as selected.
That doesn't seem like a bug to me.

By `"box-select one square at the corner of the Grid"` you mean this?: ![image.png](https://archive.blender.org/developer/F8266354/image.png) In this case the vertices of the selected edges will also be deleted, so they will not appear as selected. That doesn't seem like a bug to me.

Stanislav Blinov commented

2020-01-08 19:01:19 +01:00

One square, as in one face :) But it shows with your example too. After doing a ctrl+x, look at the stats. You should have one edge and one vert selected (should be impossible when an edge is selected), and switching to vertex mode will only have one corner vert selected.

EDIT: furthermore, switching back to edge mode will then still select an edge (from one vertex), and this time with 2 verts. :-=\

One square, as in one face :) But it shows with your example too. After doing a ctrl+x, look at the stats. You should have one edge and **one** vert selected (should be impossible when an edge is selected), and switching to vertex mode will only have one corner vert selected. EDIT: furthermore, switching back to edge mode will then still select an edge (from **one** vertex), and this time with 2 verts. :-=\

Germano Cavalcante commented

2020-01-08 20:07:01 +01:00

Changed status from 'Needs User Info' to: 'Confirmed'

Germano Cavalcante commented

2020-01-08 20:07:01 +01:00

Added subscriber: @ideasman42

Germano Cavalcante commented

2020-01-08 20:07:02 +01:00

I can confirm. The resulting edge is selected but one of its vertices is not.
Theoretically in code this is possible, but for the user this can get in the way of operations like transform for example.

This patch would solve most cases with this incosistence.

diff --git a/source/blender/bmesh/operators/bmo_dissolve.c b/source/blender/bmesh/operators/bmo_dissolve.c
index 6c662323ec1..573971136fb 100644
--- a/source/blender/bmesh/operators/bmo_dissolve.c
+++ b/source/blender/bmesh/operators/bmo_dissolve.c
@@ -355,7 +355,13 @@ void bmo_dissolve_edges_exec(BMesh *bm, BMOperator *op)
     BM_ITER_MESH_MUTABLE (v, v_next, &iter, bm, BM_VERTS_OF_MESH) {
       if (BMO_vert_flag_test(bm, v, VERT_MARK)) {
         if (BM_vert_is_edge_pair(v)) {
-          BM_vert_collapse_edge(bm, v->e, v, true, true);
+          BMEdge *e_new = BM_vert_collapse_edge(bm, v->e, v, true, true);
+          if (e_new->v1->head.hflag & e_new->v2->head.hflag & BM_ELEM_SELECT) {
+            BM_elem_flag_enable(e_new, BM_ELEM_SELECT);
+          }
+          else {
+            BM_elem_flag_disable(e_new, BM_ELEM_SELECT);
+          }
         }
       }
     }

But the real solution might be to flush the mesh after calling the operator.
I don't know if this qualifies as a bug or known issue.
@ideasman42, what do you think?

I can confirm. The resulting edge is selected but one of its vertices is not. Theoretically in code this is possible, but for the user this can get in the way of operations like transform for example. This patch would solve most cases with this incosistence. ``` diff --git a/source/blender/bmesh/operators/bmo_dissolve.c b/source/blender/bmesh/operators/bmo_dissolve.c index 6c662323ec1..573971136fb 100644 --- a/source/blender/bmesh/operators/bmo_dissolve.c +++ b/source/blender/bmesh/operators/bmo_dissolve.c @@ -355,7 +355,13 @@ void bmo_dissolve_edges_exec(BMesh *bm, BMOperator *op) BM_ITER_MESH_MUTABLE (v, v_next, &iter, bm, BM_VERTS_OF_MESH) { if (BMO_vert_flag_test(bm, v, VERT_MARK)) { if (BM_vert_is_edge_pair(v)) { - BM_vert_collapse_edge(bm, v->e, v, true, true); + BMEdge *e_new = BM_vert_collapse_edge(bm, v->e, v, true, true); + if (e_new->v1->head.hflag & e_new->v2->head.hflag & BM_ELEM_SELECT) { + BM_elem_flag_enable(e_new, BM_ELEM_SELECT); + } + else { + BM_elem_flag_disable(e_new, BM_ELEM_SELECT); + } } } } ``` But the real solution might be to flush the mesh after calling the operator. I don't know if this qualifies as a bug or known issue. @ideasman42, what do you think?

Stanislav Blinov commented

2020-01-08 20:14:21 +01:00

It's not just transform, simple mode switching can also bring unexpected results (see the video linked in the description).

Bastien Montagne commented

2020-01-22 11:38:39 +01:00

Added subscriber: @mont29

Bastien Montagne commented

2020-01-22 11:38:39 +01:00

Would consider this as a bug for now, afaik tools should always leave selection in a state that is consistent with current selection mode?

Philipp Oeser removed the

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'Dissolve' operator leaves inconsistent selection #72806