Weight Paint: Implement a new Lock-Relative mode.

This check box alters how weights are displayed and painted,
similar to Multi Paint, but in a different way. Specifically,
weights are presented as if all locked vertex groups were
deleted, and the remaining deform groups normalized.

The new feature is intended for use when balancing weights within
a group of bones while all others are locked. Enabling the option
presents weight as if the locked bones didn't exist, and their
weight was proportionally redistributed to the editable bones.

Conversely, the Multi-Paint feature allows balancing a group of
bones as a whole against all unselected bones, while ignoring
weight distribution within the selected group.

This mode also allows temporarily viewing non-normalized weights
as if they were normalized, without actually changing the values.

Differential Revision: https://developer.blender.org/D3837

1 files changed, 29 insertions, 9 deletions

diff --git a/source/blender/editors/sculpt_paint/paint_vertex_weight_ops.c b/source/blender/editors/sculpt_paint/paint_vertex_weight_ops.c
index 4b8990c1b5d..5c408933559 100644
--- a/source/blender/editors/sculpt_paint/paint_vertex_weight_ops.c
+++ b/source/blender/editors/sculpt_paint/paint_vertex_weight_ops.c
@@ -212,12 +212,22 @@ static int weight_sample_invoke(bContext *C, wmOperator *op, const wmEvent *even
       Brush *brush = BKE_paint_brush(&ts->wpaint->paint);
       const int vgroup_active = vc.obact->actdef - 1;
       float vgroup_weight = BKE_defvert_find_weight(&me->dvert[v_idx_best], vgroup_active);
+      const int defbase_tot = BLI_listbase_count(&vc.obact->defbase);
+      bool use_lock_relative = ts->wpaint_lock_relative;
+      bool *defbase_locked = NULL, *defbase_unlocked = NULL;
+
+      if (use_lock_relative) {
+        defbase_locked = BKE_object_defgroup_lock_flags_get(vc.obact, defbase_tot);
+        defbase_unlocked = BKE_object_defgroup_validmap_get(vc.obact, defbase_tot);
+
+        use_lock_relative = BKE_object_defgroup_check_lock_relative(
+            defbase_locked, defbase_unlocked, vgroup_active);
+      }
 
       /* use combined weight in multipaint mode,
        * since that's what is displayed to the user in the colors */
       if (ts->multipaint) {
         int defbase_tot_sel;
-        const int defbase_tot = BLI_listbase_count(&vc.obact->defbase);
         bool *defbase_sel = BKE_object_defgroup_selected_get(
             vc.obact, defbase_tot, &defbase_tot_sel);
 
@@ -227,20 +237,30 @@ static int weight_sample_invoke(bContext *C, wmOperator *op, const wmEvent *even
                 vc.obact, defbase_tot, defbase_sel, defbase_sel, &defbase_tot_sel);
           }
 
-          vgroup_weight = BKE_defvert_multipaint_collective_weight(&me->dvert[v_idx_best],
-                                                                   defbase_tot,
-                                                                   defbase_sel,
-                                                                   defbase_tot_sel,
-                                                                   ts->auto_normalize);
+          use_lock_relative = use_lock_relative &&
+                              BKE_object_defgroup_check_lock_relative_multi(
+                                  defbase_tot, defbase_locked, defbase_sel, defbase_tot_sel);
 
-          /* If auto-normalize is enabled, but weights are not normalized,
-           * the value can exceed 1. */
-          CLAMP(vgroup_weight, 0.0f, 1.0f);
+          bool is_normalized = ts->auto_normalize || use_lock_relative;
+          vgroup_weight = BKE_defvert_multipaint_collective_weight(
+              &me->dvert[v_idx_best], defbase_tot, defbase_sel, defbase_tot_sel, is_normalized);
         }
 
         MEM_freeN(defbase_sel);
       }
 
+      if (use_lock_relative) {
+        BKE_object_defgroup_split_locked_validmap(
+            defbase_tot, defbase_locked, defbase_unlocked, defbase_locked, defbase_unlocked);
+
+        vgroup_weight = BKE_defvert_lock_relative_weight(
+            vgroup_weight, &me->dvert[v_idx_best], defbase_tot, defbase_locked, defbase_unlocked);
+      }
+
+      MEM_SAFE_FREE(defbase_locked);
+      MEM_SAFE_FREE(defbase_unlocked);
+
+      CLAMP(vgroup_weight, 0.0f, 1.0f);
       BKE_brush_weight_set(vc.scene, brush, vgroup_weight);
       changed = true;
     }