From 2beff6197e98ec3bcf92f9473953b32fcf89c373 Mon Sep 17 00:00:00 2001
From: Fredrik Hansson <fredrikh>
Date: Fri, 23 Jul 2021 18:46:19 -0300
Subject: Weld Modifier: add "loose_edges" option

This improve the cloth modeling workflow by allowing you to weld only the
edges that are used for the sewing forces.

Reviewed By: mano-wii, weasel

Differential Revision: https://developer.blender.org/D10710
---
 source/blender/makesdna/DNA_modifier_types.h  | 1 +
 source/blender/makesrna/intern/rna_modifier.c | 6 ++++++
 source/blender/modifiers/intern/MOD_weld.c    | 7 +++++++
 3 files changed, 14 insertions(+)

(limited to 'source/blender')

diff --git a/source/blender/makesdna/DNA_modifier_types.h b/source/blender/makesdna/DNA_modifier_types.h
index 401b49f2ee8..99c346bf589 100644
--- a/source/blender/makesdna/DNA_modifier_types.h
+++ b/source/blender/makesdna/DNA_modifier_types.h
@@ -2023,6 +2023,7 @@ typedef struct WeldModifierData {
 /* WeldModifierData->flag */
 enum {
   MOD_WELD_INVERT_VGROUP = (1 << 0),
+  MOD_WELD_LOOSE_EDGES = (1 << 1),
 };
 
 /* #WeldModifierData.mode */
diff --git a/source/blender/makesrna/intern/rna_modifier.c b/source/blender/makesrna/intern/rna_modifier.c
index 5fddb0f18a5..388f587dfb4 100644
--- a/source/blender/makesrna/intern/rna_modifier.c
+++ b/source/blender/makesrna/intern/rna_modifier.c
@@ -6279,6 +6279,12 @@ static void rna_def_modifier_weld(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Invert", "Invert vertex group influence");
   RNA_def_property_update(prop, 0, "rna_Modifier_update");
 
+  prop = RNA_def_property(srna, "loose_edges", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag", MOD_WELD_LOOSE_EDGES);
+  RNA_def_property_ui_text(
+      prop, "Only Loose Edges", "Collapse edges without faces, cloth sewing edges");
+  RNA_def_property_update(prop, 0, "rna_Modifier_update");
+
   RNA_define_lib_overridable(false);
 }
 
diff --git a/source/blender/modifiers/intern/MOD_weld.c b/source/blender/modifiers/intern/MOD_weld.c
index fe2d699aea8..b1fa2a7d912 100644
--- a/source/blender/modifiers/intern/MOD_weld.c
+++ b/source/blender/modifiers/intern/MOD_weld.c
@@ -1735,6 +1735,9 @@ static Mesh *weldModifier_doWeld(WeldModifierData *wmd,
       uint v1 = me->v1;
       uint v2 = me->v2;
 
+      if (wmd->flag & MOD_WELD_LOOSE_EDGES && (me->flag & ME_LOOSEEDGE) == 0) {
+        continue;
+      }
       while (v1 != vert_dest_map[v1]) {
         v1 = vert_dest_map[v1];
       }
@@ -2019,11 +2022,15 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel)
 
   PointerRNA ob_ptr;
   PointerRNA *ptr = modifier_panel_get_property_pointers(panel, &ob_ptr);
+  int weld_mode = RNA_enum_get(ptr, "mode");
 
   uiLayoutSetPropSep(layout, true);
 
   uiItemR(layout, ptr, "mode", 0, NULL, ICON_NONE);
   uiItemR(layout, ptr, "merge_threshold", 0, IFACE_("Distance"), ICON_NONE);
+  if (weld_mode == MOD_WELD_MODE_CONNECTED) {
+    uiItemR(layout, ptr, "loose_edges", 0, NULL, ICON_NONE);
+  }
   modifier_vgroup_ui(layout, ptr, &ob_ptr, "vertex_group", "invert_vertex_group", NULL);
 
   modifier_panel_end(layout, ptr);
-- 
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