scripts/startup/bl_ui/properties_data_armature.py

@@ -81,6 +81,9 @@ class DATA_PT_display(ArmatureButtonsPanel, Panel):
         sub.active = arm.show_axes
         sub.prop(arm, "axes_position", text="Position")
 
+        sub = col.row(align=True)
+        sub.prop(arm, "relation_line_position", text="Relations", expand=True)
+
 
 class DATA_MT_bone_group_context_menu(Menu):
     bl_label = "Bone Group Specials"

source/blender/blenloader/intern/versioning_280.c

@@ -3639,7 +3639,7 @@ void blo_do_versions_280(FileData *fd, Library *UNUSED(lib), Main *bmain)
     }
 
     LISTBASE_FOREACH (bArmature *, arm, &bmain->armatures) {
-      arm->flag &= ~(ARM_FLAG_UNUSED_1 | ARM_FLAG_UNUSED_5 | ARM_FLAG_UNUSED_6 |
+      arm->flag &= ~(ARM_FLAG_UNUSED_1 | ARM_DRAW_RELATION_FROM_HEAD | ARM_FLAG_UNUSED_6 |
                      ARM_FLAG_UNUSED_7 | ARM_FLAG_UNUSED_12);
     }
 

source/blender/draw/engines/overlay/overlay_armature.cc

@@ -2023,6 +2023,20 @@ static void pchan_draw_ik_lines(ArmatureDrawContext *ctx,
   }
 }
 
+static void draw_bone_bone_relationship_line(ArmatureDrawContext *ctx,
+                                             const float bone_head[3],
+                                             const float parent_head[3],
+                                             const float parent_tail[3],
+                                             const eArmature_Flag armature_flags)
+{
+  if (armature_flags & ARM_DRAW_RELATION_FROM_HEAD) {
+    drw_shgroup_bone_relationship_lines(ctx, bone_head, parent_head);
+  }
+  else {
+    drw_shgroup_bone_relationship_lines(ctx, bone_head, parent_tail);
+  }
+}
+
 static void draw_bone_relations(ArmatureDrawContext *ctx,
                                 EditBone *ebone,
                                 bPoseChannel *pchan,
@@ -2036,7 +2050,8 @@ static void draw_bone_relations(ArmatureDrawContext *ctx,
        * since riggers will want to know about the links between bones
        */
       if ((boneflag & BONE_CONNECTED) == 0) {
-        drw_shgroup_bone_relationship_lines(ctx, ebone->head, ebone->parent->tail);
+        draw_bone_bone_relationship_line(
+            ctx, ebone->head, ebone->parent->head, ebone->parent->tail, eArmature_Flag(arm->flag));
       }
     }
   }
@@ -2047,7 +2062,11 @@ static void draw_bone_relations(ArmatureDrawContext *ctx,
       if ((boneflag & BONE_SELECTED) ||
           (pchan->parent->bone && (pchan->parent->bone->flag & BONE_SELECTED))) {
         if ((boneflag & BONE_CONNECTED) == 0) {
-          drw_shgroup_bone_relationship_lines(ctx, pchan->pose_head, pchan->parent->pose_tail);
+          draw_bone_bone_relationship_line(ctx,
+                                           pchan->pose_head,
+                                           pchan->parent->pose_head,
+                                           pchan->parent->pose_tail,
+                                           eArmature_Flag(arm->flag));
         }
       }
     }

source/blender/makesdna/DNA_armature_types.h

@@ -154,9 +154,12 @@ typedef enum eArmature_Flag {
   ARM_DRAWAXES = (1 << 2),
   ARM_DRAWNAMES = (1 << 3),
   ARM_POSEMODE = (1 << 4),
-  ARM_FLAG_UNUSED_5 = (1 << 5), /* cleared */
-  ARM_FLAG_UNUSED_6 = (1 << 6), /* cleared */
-  ARM_FLAG_UNUSED_7 = (1 << 7),
+  /** Position of the parent-child relation lines on the bone (cleared = drawn
+   * from the tail, set = drawn from the head). Only controls the parent side of
+   * the line; the child side is always drawn to the head of the bone. */
+  ARM_DRAW_RELATION_FROM_HEAD = (1 << 5), /* Cleared in versioning of pre-2.80 files. */
+  ARM_FLAG_UNUSED_6 = (1 << 6),           /* cleared */
+  ARM_FLAG_UNUSED_7 = (1 << 7),           /* cleared */
   ARM_MIRROR_EDIT = (1 << 8),
   ARM_FLAG_UNUSED_9 = (1 << 9),
   /** Made option negative, for backwards compatibility. */

source/blender/makesrna/intern/rna_armature.c

@@ -653,6 +653,30 @@ static void rna_Armature_transform(bArmature *arm, float mat[16])
   ED_armature_transform(arm, (const float(*)[4])mat, true);
 }
 
+static int rna_Armature_relation_line_position_get(PointerRNA *ptr)
+{
+  bArmature *arm = (bArmature *)ptr->data;
+  /* Translate the bitflag to an EnumPropertyItem prop_relation_lines_items item ID. */
+  return (arm->flag & ARM_DRAW_RELATION_FROM_HEAD) ? 1 : 0;
+}
+
+static void rna_Armature_relation_line_position_set(PointerRNA *ptr, const int value)
+{
+  bArmature *arm = (bArmature *)ptr->data;
+
+  /* Translate the EnumPropertyItem prop_relation_lines_items item ID to a bitflag */
+  switch (value) {
+    case 0:
+      arm->flag &= ~ARM_DRAW_RELATION_FROM_HEAD;
+      break;
+    case 1:
+      arm->flag |= ARM_DRAW_RELATION_FROM_HEAD;
+      break;
+    default:
+      return;
+  }
+}
+
 #else
 
 void rna_def_bone_curved_common(StructRNA *srna, bool is_posebone, bool is_editbone)
@@ -1460,6 +1484,11 @@ static void rna_def_armature(BlenderRNA *brna)
        "Show Armature in binding pose state (no posing possible)"},
       {0, NULL, 0, NULL, NULL},
   };
+  static const EnumPropertyItem prop_relation_lines_items[] = {
+      {0, "TAIL", 0, "Tail", "Draw the relationship line from the parent tail to the child head"},
+      {1, "HEAD", 0, "Head", "Draw the relationship line from the parent head to the child head"},
+      {0, NULL, 0, NULL, NULL},
+  };
 
   srna = RNA_def_struct(brna, "Armature", "ID");
   RNA_def_struct_ui_text(
@@ -1554,6 +1583,20 @@ static void rna_def_armature(BlenderRNA *brna)
                            "closer to the tip; decreasing moves it closer to the root");
   RNA_def_property_update(prop, 0, "rna_Armature_redraw_data");
 
+  RNA_define_verify_sdna(false); /* This property does not live in DNA. */
+  prop = RNA_def_property(srna, "relation_line_position", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, prop_relation_lines_items);
+  RNA_def_property_ui_text(prop,
+                           "Relation Line Position",
+                           "The start position of the relation lines from parent to child bones");
+  RNA_def_property_update(prop, 0, "rna_Armature_redraw_data");
+  RNA_def_property_flag(prop, PROP_LIB_EXCEPTION);
+  RNA_def_property_enum_funcs(prop,
+                              "rna_Armature_relation_line_position_get",
+                              "rna_Armature_relation_line_position_set",
+                              /*item function*/ NULL);
+  RNA_define_verify_sdna(true); /* Restore default. */
+
   prop = RNA_def_property(srna, "show_names", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "flag", ARM_DRAWNAMES);
   RNA_def_property_ui_text(prop, "Display Names", "Display bone names");