From e32457952b45e5df7c3fc7d3e948e1403c7452da Mon Sep 17 00:00:00 2001
From: Cody Winchester <CodyWinch>
Date: Wed, 12 Feb 2020 10:34:35 +0100
Subject: [PATCH] Modifiers: Hook Modifier add invert vgroup option

Adds the invert group optin to the hook modifier.

Differential Revision: https://developer.blender.org/D6817
---
 release/scripts/startup/bl_ui/properties_data_modifier.py | 4 +++-
 source/blender/makesdna/DNA_modifier_types.h              | 1 +
 source/blender/makesrna/intern/rna_modifier.c             | 5 +++++
 source/blender/modifiers/intern/MOD_hook.c                | 8 +++++++-
 4 files changed, 16 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 b91c7f71843..7dadbd427fd 100644
--- a/release/scripts/startup/bl_ui/properties_data_modifier.py
+++ b/release/scripts/startup/bl_ui/properties_data_modifier.py
@@ -454,7 +454,9 @@ class DATA_PT_modifiers(ModifierButtonsPanel, Panel):
             col.prop_search(md, "subtarget", md.object.data, "bones", text="")
         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')
 
         layout.separator()
 
diff --git a/source/blender/makesdna/DNA_modifier_types.h b/source/blender/makesdna/DNA_modifier_types.h
index 2c0d34fdccf..474e9107bc4 100644
--- a/source/blender/makesdna/DNA_modifier_types.h
+++ b/source/blender/makesdna/DNA_modifier_types.h
@@ -703,6 +703,7 @@ typedef struct ArmatureModifierData {
 
 enum {
   MOD_HOOK_UNIFORM_SPACE = (1 << 0),
+  MOD_HOOK_INVERT_VGROUP = (1 << 1)
 };
 
 /* same as WarpModifierFalloff */
diff --git a/source/blender/makesrna/intern/rna_modifier.c b/source/blender/makesrna/intern/rna_modifier.c
index 0d953728c5e..c6898120bfa 100644
--- a/source/blender/makesrna/intern/rna_modifier.c
+++ b/source/blender/makesrna/intern/rna_modifier.c
@@ -2550,6 +2550,11 @@ static void rna_def_modifier_hook(BlenderRNA *brna)
       func, "indices", 1, NULL, INT_MIN, INT_MAX, "", "Vertex Indices", 0, INT_MAX);
   RNA_def_property_array(parm, RNA_MAX_ARRAY_LENGTH);
   RNA_def_parameter_flags(parm, PROP_DYNAMIC, PARM_REQUIRED);
+
+  prop = RNA_def_property(srna, "invert_vertex_group", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag", MOD_HOOK_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_softbody(BlenderRNA *brna)
diff --git a/source/blender/modifiers/intern/MOD_hook.c b/source/blender/modifiers/intern/MOD_hook.c
index b1a662c8667..6b5d7233b60 100644
--- a/source/blender/modifiers/intern/MOD_hook.c
+++ b/source/blender/modifiers/intern/MOD_hook.c
@@ -143,6 +143,8 @@ struct HookData_cb {
 
   float mat_uniform[3][3];
   float mat[4][4];
+
+  bool invert_vgroup;
 };
 
 static float hook_falloff(const struct HookData_cb *hd, const float len_sq)
@@ -236,7 +238,8 @@ static void hook_co_apply(struct HookData_cb *hd, const int j)
 
   if (fac) {
     if (hd->dvert) {
-      fac *= defvert_find_weight(&hd->dvert[j], hd->defgrp_index);
+      fac *= hd->invert_vgroup ? 1.0f - defvert_find_weight(&hd->dvert[j], hd->defgrp_index) :
+                                 defvert_find_weight(&hd->dvert[j], hd->defgrp_index);
     }
 
     if (fac) {
@@ -259,6 +262,7 @@ static void deformVerts_do(HookModifierData *hmd,
   float dmat[4][4];
   int i, *index_pt;
   struct HookData_cb hd;
+  const bool invert_vgroup = (hmd->flag & MOD_HOOK_INVERT_VGROUP) != 0;
 
   if (hmd->curfalloff == NULL) {
     /* should never happen, but bad lib linking could cause it */
@@ -283,6 +287,8 @@ static void deformVerts_do(HookModifierData *hmd,
   hd.use_falloff = (hd.falloff_sq != 0.0f);
   hd.use_uniform = (hmd->flag & MOD_HOOK_UNIFORM_SPACE) != 0;
 
+  hd.invert_vgroup = invert_vgroup;
+
   if (hd.use_uniform) {
     copy_m3_m4(hd.mat_uniform, hmd->parentinv);
     mul_v3_m3v3(hd.cent, hd.mat_uniform, hmd->cent);