Vertices will always merge when "Clipping" is checked on a mirror modifier #103175

New Issue

Andrew Price · 2022-12-13T04:08:44+01:00

Andrew Price commented

2022-12-13 04:08:44 +01:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 527.56

Blender Version
Broken: version: 3.4.0, branch: blender-v3.4-release, commit date: 2022-12-06 18:46, hash: a95bf1ac01
Worked: Not sure

Short description of error
Despite "merge" being unchecked, if you have clipping checked on a mirror modifier it will behave as if merge is turned on.

Exact steps for others to reproduce the error

Scale down the default cube to 0.1. Apply scale.
Add a loop cut down the middle and delete half the mesh
Add a mirror modifier and turn off merge
Select the edge loop you just created and move it very slightly off center (so there's a gap)
Turn on clipping (but leave merge off)
In edit move move the edge loop again and you'll see it auto-merge the vertices close to the edge. If you reduce the merge distance it will not merge them, showing that when clipping is enabled it will auto merge verts despite that being unchecked.

Attached example:
clipping demo.blend

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 527.56 **Blender Version** Broken: version: 3.4.0, branch: blender-v3.4-release, commit date: 2022-12-06 18:46, hash: `a95bf1ac01` Worked: Not sure **Short description of error** Despite "merge" being unchecked, if you have clipping checked on a mirror modifier it will behave as if merge is turned on. **Exact steps for others to reproduce the error** 1. Scale down the default cube to 0.1. Apply scale. 2. Add a loop cut down the middle and delete half the mesh 3. Add a mirror modifier and turn off merge 4. Select the edge loop you just created and move it very slightly off center (so there's a gap) 5. Turn on clipping (but leave merge off) 6. In edit move move the edge loop again and you'll see it auto-merge the vertices close to the edge. If you reduce the merge distance it will not merge them, showing that when clipping is enabled it will auto merge verts despite that being unchecked. Attached example: [clipping demo.blend](https://archive.blender.org/developer/F14054931/clipping_demo.blend)

Andrew Price commented

2022-12-13 04:08:44 +01:00

Added subscriber: @AndrewPrice

Pratik Borhade commented

2022-12-13 08:02:53 +01:00

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

Pratik Borhade commented

2022-12-13 08:02:57 +01:00

Added subscriber: @PratikPB2123

Philipp Oeser commented

2022-12-13 13:36:41 +01:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2022-12-13 13:36:41 +01:00

NOTE: these are not really merged (you can check e.g. with smooth shading, you will still get a sharp edge, so you still have "doubles" there), the thing is you just cant move the loop/verts from the clipping plane anymore, it is "stuck" there because the transform system applies the new values thus you'll always stay in the clip threshold...

Germano Cavalcante commented

2022-12-13 18:03:38 +01:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2022-12-13 18:03:38 +01:00

The transform code could easily be edited to ignore the threshold value if merge is disabled.
But as we can see in the manual , using the merge threshold for clipping seems to be the expected behavior.
So this seems to be a design issue.
The "Merge Distance" property should not be grayed out if "Clipping" is enabled.

One solution would be to change the mirror modifier panel to:

diff --git a/source/blender/modifiers/intern/MOD_mirror.c b/source/blender/modifiers/intern/MOD_mirror.c
index f1a36c04453..d812e686ae9 100644
--- a/source/blender/modifiers/intern/MOD_mirror.c
+++ b/source/blender/modifiers/intern/MOD_mirror.c
@@ -143,14 +143,6 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel)
 
   uiItemR(col, ptr, "mirror_object", 0, NULL, ICON_NONE);
 
-  uiItemR(col, ptr, "use_clip", 0, IFACE_("Clipping"), ICON_NONE);
-
-  row = uiLayoutRowWithHeading(col, true, IFACE_("Merge"));
-  uiItemR(row, ptr, "use_mirror_merge", 0, "", ICON_NONE);
-  sub = uiLayoutRow(row, true);
-  uiLayoutSetActive(sub, RNA_boolean_get(ptr, "use_mirror_merge"));
-  uiItemR(sub, ptr, "merge_threshold", 0, "", ICON_NONE);
-
   bool is_bisect_set[3];
   RNA_boolean_get_array(ptr, "use_bisect_axis", is_bisect_set);
 
@@ -158,6 +150,15 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel)
   uiLayoutSetActive(sub, is_bisect_set[0] || is_bisect_set[1] || is_bisect_set[2]);
   uiItemR(sub, ptr, "bisect_threshold", 0, IFACE_("Bisect Distance"), ICON_NONE);
 
+  sub = uiLayoutColumn(col, false);
+  uiLayoutSetActive(sub,
+                    RNA_boolean_get(ptr, "use_clip") || RNA_boolean_get(ptr, "use_mirror_merge"));
+  uiItemR(sub, ptr, "merge_threshold", 0, IFACE_("Clip/Merge Distance"), ICON_NONE);
+
+  sub = uiLayoutRow(col, true);
+  uiItemR(sub, ptr, "use_clip", 0, IFACE_("Clipping"), ICON_NONE);
+  uiItemR(sub, ptr, "use_mirror_merge", 0, IFACE_("Merging"), ICON_NONE);
+
   modifier_panel_end(layout, ptr);
 }

This looks like something for someone on the #user_interface team to check.

The transform code could easily be edited to ignore the threshold value if merge is disabled. But as we can see in the [manual ](https://docs.blender.org/manual/en/3.5/modeling/modifiers/generate/mirror.html#bpy-types-mirrormodifier), using the merge threshold for clipping seems to be the expected behavior. So this seems to be a design issue. The "Merge Distance" property should not be grayed out if "Clipping" is enabled. One solution would be to change the mirror modifier panel to: ![image.png](https://archive.blender.org/developer/F14055841/image.png) ``` diff --git a/source/blender/modifiers/intern/MOD_mirror.c b/source/blender/modifiers/intern/MOD_mirror.c index f1a36c04453..d812e686ae9 100644 --- a/source/blender/modifiers/intern/MOD_mirror.c +++ b/source/blender/modifiers/intern/MOD_mirror.c @@ -143,14 +143,6 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel) uiItemR(col, ptr, "mirror_object", 0, NULL, ICON_NONE); - uiItemR(col, ptr, "use_clip", 0, IFACE_("Clipping"), ICON_NONE); - - row = uiLayoutRowWithHeading(col, true, IFACE_("Merge")); - uiItemR(row, ptr, "use_mirror_merge", 0, "", ICON_NONE); - sub = uiLayoutRow(row, true); - uiLayoutSetActive(sub, RNA_boolean_get(ptr, "use_mirror_merge")); - uiItemR(sub, ptr, "merge_threshold", 0, "", ICON_NONE); - bool is_bisect_set[3]; RNA_boolean_get_array(ptr, "use_bisect_axis", is_bisect_set); @@ -158,6 +150,15 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel) uiLayoutSetActive(sub, is_bisect_set[0] || is_bisect_set[1] || is_bisect_set[2]); uiItemR(sub, ptr, "bisect_threshold", 0, IFACE_("Bisect Distance"), ICON_NONE); + sub = uiLayoutColumn(col, false); + uiLayoutSetActive(sub, + RNA_boolean_get(ptr, "use_clip") || RNA_boolean_get(ptr, "use_mirror_merge")); + uiItemR(sub, ptr, "merge_threshold", 0, IFACE_("Clip/Merge Distance"), ICON_NONE); + + sub = uiLayoutRow(col, true); + uiItemR(sub, ptr, "use_clip", 0, IFACE_("Clipping"), ICON_NONE); + uiItemR(sub, ptr, "use_mirror_merge", 0, IFACE_("Merging"), ICON_NONE); + modifier_panel_end(layout, ptr); } ``` This looks like something for someone on the #user_interface team to check.

Philipp Oeser removed the

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Vertices will always merge when "Clipping" is checked on a mirror modifier #103175