Simple Deform modifier: invert vgroup option

D1839 from @Orgold

4 files changed, 21 insertions, 2 deletions

diff --git a/release/scripts/startup/bl_ui/properties_data_modifier.py b/release/scripts/startup/bl_ui/properties_data_modifier.py
index 30ca17567d1..cf939719ba3 100644
--- a/release/scripts/startup/bl_ui/properties_data_modifier.py
+++ b/release/scripts/startup/bl_ui/properties_data_modifier.py
@@ -788,7 +788,9 @@ class DATA_PT_modifiers(ModifierButtonsPanel, Panel):
 
         col = split.column()
         col.label(text="Vertex Group:")
-        col.prop_search(md, "vertex_group", ob, "vertex_groups", text="")
+        row = col.row(align=True)
+        row.prop_search(md, "vertex_group", ob, "vertex_groups", text="")
+        row.prop(md, "invert_vertex_group", text="", icon='ARROW_LEFTRIGHT')
 
         split = layout.split()
 
diff --git a/source/blender/makesdna/DNA_modifier_types.h b/source/blender/makesdna/DNA_modifier_types.h
index c2159510937..457db70cd28 100644
--- a/source/blender/makesdna/DNA_modifier_types.h
+++ b/source/blender/makesdna/DNA_modifier_types.h
@@ -848,10 +848,17 @@ typedef struct SimpleDeformModifierData {
 
 	char mode;              /* deform function */
 	char axis;              /* lock axis (for taper and strech) */
-	char pad[2];
+	char flag;
+	char pad;
 
 } SimpleDeformModifierData;
 
+/* SimpleDeform->flag */
+enum {
+	MOD_SIMPLEDEFORM_FLAG_INVERT_VGROUP = (1 << 0),
+};
+
+
 enum {
 	MOD_SIMPLEDEFORM_MODE_TWIST   = 1,
 	MOD_SIMPLEDEFORM_MODE_BEND    = 2,
diff --git a/source/blender/makesrna/intern/rna_modifier.c b/source/blender/makesrna/intern/rna_modifier.c
index 571d7fb5447..0c4b3ba485d 100644
--- a/source/blender/makesrna/intern/rna_modifier.c
+++ b/source/blender/makesrna/intern/rna_modifier.c
@@ -3174,6 +3174,11 @@ static void rna_def_modifier_simpledeform(BlenderRNA *brna)
 	RNA_def_property_boolean_sdna(prop, NULL, "axis", MOD_SIMPLEDEFORM_LOCK_AXIS_Y);
 	RNA_def_property_ui_text(prop, "Lock Y Axis", "Do not allow deformation along the Y axis");
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
+
+	prop = RNA_def_property(srna, "invert_vertex_group", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", MOD_SIMPLEDEFORM_FLAG_INVERT_VGROUP);
+	RNA_def_property_ui_text(prop, "Invert", "Invert vertex group influence");
+	RNA_def_property_update(prop, 0, "rna_Modifier_update");
 }
 
 static void rna_def_modifier_surface(BlenderRNA *brna)
diff --git a/source/blender/modifiers/intern/MOD_simpledeform.c b/source/blender/modifiers/intern/MOD_simpledeform.c
index f4fbfa74076..588b56d6aba 100644
--- a/source/blender/modifiers/intern/MOD_simpledeform.c
+++ b/source/blender/modifiers/intern/MOD_simpledeform.c
@@ -214,10 +214,15 @@ static void SimpleDeformModifier_do(SimpleDeformModifierData *smd, struct Object
 	}
 
 	modifier_get_vgroup(ob, dm, smd->vgroup_name, &dvert, &vgroup);
+	const bool invert_vgroup = (smd->flag & MOD_SIMPLEDEFORM_FLAG_INVERT_VGROUP) != 0;
 
 	for (i = 0; i < numVerts; i++) {
 		float weight = defvert_array_find_weight_safe(dvert, i, vgroup);
 
+		if (invert_vgroup) {
+			weight = 1.0f - weight;
+		}
+
 		if (weight != 0.0f) {
 			float co[3], dcut[3] = {0.0f, 0.0f, 0.0f};