Cast modifier: Add invert vgroup option.

Adds the Invert Vertex Group weight option to the Cast modifier.
Uses the same setup as similar modifiers invert weight.
Adds a boolean invert property next to the vertex group string in the modifier
and subtracts the current vertex weight from 1.0f if it is turned on.

Differential Revision: https://developer.blender.org/D6671

Minor modifications by @mont29.

1 files changed, 9 insertions, 2 deletions

diff --git a/source/blender/modifiers/intern/MOD_cast.c b/source/blender/modifiers/intern/MOD_cast.c
index 0bf1dd8e2b3..b070a3c7127 100644
--- a/source/blender/modifiers/intern/MOD_cast.c
+++ b/source/blender/modifiers/intern/MOD_cast.c
@@ -105,6 +105,7 @@ static void sphere_do(CastModifierData *cmd,
                       int numVerts)
 {
   MDeformVert *dvert = NULL;
+  const bool invert_vgroup = (cmd->flag & MOD_CAST_INVERT_VGROUP) != 0;
 
   Object *ctrl_ob = NULL;
 
@@ -198,7 +199,9 @@ static void sphere_do(CastModifierData *cmd,
     }
 
     if (dvert) {
-      const float weight = defvert_find_weight(&dvert[i], defgrp_index);
+      const float weight = invert_vgroup ? 1.0f - defvert_find_weight(&dvert[i], defgrp_index) :
+                                           defvert_find_weight(&dvert[i], defgrp_index);
+
       if (weight == 0.0f) {
         continue;
       }
@@ -240,6 +243,8 @@ static void cuboid_do(CastModifierData *cmd,
                       int numVerts)
 {
   MDeformVert *dvert = NULL;
+  const bool invert_vgroup = (cmd->flag & MOD_CAST_INVERT_VGROUP) != 0;
+
   Object *ctrl_ob = NULL;
 
   int i, defgrp_index;
@@ -365,7 +370,9 @@ static void cuboid_do(CastModifierData *cmd,
     }
 
     if (dvert) {
-      const float weight = defvert_find_weight(&dvert[i], defgrp_index);
+      const float weight = invert_vgroup ? 1.0f - defvert_find_weight(&dvert[i], defgrp_index) :
+                                           defvert_find_weight(&dvert[i], defgrp_index);
+
       if (weight == 0.0f) {
         continue;
       }