Fix #34818: Sculpting Mode only rotates around geometry origin (bring bug back)

Made it so average coordinate of previous stroke is used as
a viewport rotation center when Rotate Around Selection is
enabled in user preferences.

4 files changed, 38 insertions, 4 deletions

diff --git a/source/blender/blenkernel/BKE_paint.h b/source/blender/blenkernel/BKE_paint.h
index f616da4985f..ff5efd3b02b 100644
--- a/source/blender/blenkernel/BKE_paint.h
+++ b/source/blender/blenkernel/BKE_paint.h
@@ -158,6 +158,9 @@ typedef struct SculptSession {
 	/* last paint/sculpt stroke location */
 	int last_stroke_valid;
 	float last_stroke[3];
+
+	float average_stroke_accum[3];
+	int average_stroke_counter;
 } SculptSession;
 
 void free_sculptsession(struct Object *ob);
diff --git a/source/blender/editors/include/ED_sculpt.h b/source/blender/editors/include/ED_sculpt.h
index 0381ecc1fb3..a50a8a50eaa 100644
--- a/source/blender/editors/include/ED_sculpt.h
+++ b/source/blender/editors/include/ED_sculpt.h
@@ -44,6 +44,7 @@ void sculpt_get_redraw_planes(float planes[4][4], struct ARegion *ar,
                               struct RegionView3D *rv3d, struct Object *ob);
 void ED_sculpt_force_update(struct bContext *C);
 float *ED_sculpt_get_last_stroke(struct Object *ob);
+void ED_sculpt_get_average_stroke(struct Object *ob, float stroke[3]);
 int ED_sculpt_minmax(struct bContext *C, float min[3], float max[3]);
 int ED_sculpt_mask_layers_ensure(struct Object *ob,
                                   struct MultiresModifierData *mmd);
diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 75a00ba4f76..d1702c8f505 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -118,6 +118,17 @@ float *ED_sculpt_get_last_stroke(struct Object *ob)
 	return (ob && ob->sculpt && ob->sculpt->last_stroke_valid) ? ob->sculpt->last_stroke : NULL;
 }
 
+void ED_sculpt_get_average_stroke(Object *ob, float stroke[3])
+{
+	if (ob->sculpt->last_stroke_valid) {
+		float fac = 1.0f / ob->sculpt->average_stroke_counter;
+		mul_v3_v3fl(stroke, ob->sculpt->average_stroke_accum, fac);
+	}
+	else {
+		copy_v3_v3(stroke, ob->obmat[3]);
+	}
+}
+
 int ED_sculpt_minmax(bContext *C, float min[3], float max[3])
 {
 	Object *ob = CTX_data_active_object(C);
@@ -3015,6 +3026,8 @@ static void do_brush_action(Sculpt *sd, Object *ob, Brush *brush)
 
 	/* Only act if some verts are inside the brush area */
 	if (totnode) {
+		float location[3];
+
 		#pragma omp parallel for schedule(guided) if (sd->flags & SCULPT_USE_OPENMP)
 		for (n = 0; n < totnode; n++) {
 			sculpt_undo_push_node(ob, nodes[n],
@@ -3099,6 +3112,13 @@ static void do_brush_action(Sculpt *sd, Object *ob, Brush *brush)
 		}
 
 		MEM_freeN(nodes);
+
+		/* update average stroke position */
+		copy_v3_v3(location, ss->cache->true_location);
+		mul_m4_v3(ob->obmat, location);
+
+		add_v3_v3(ob->sculpt->average_stroke_accum, location);
+		ob->sculpt->average_stroke_counter++;
 	}
 }
 
@@ -4143,6 +4163,9 @@ static int sculpt_brush_stroke_init(bContext *C, wmOperator *op)
 	is_smooth = sculpt_any_smooth_mode(brush, NULL, mode);
 	sculpt_update_mesh_elements(scene, sd, ob, is_smooth, need_mask);
 
+	zero_v3(ob->sculpt->average_stroke_accum);
+	ob->sculpt->average_stroke_counter = 0;
+
 	return 1;
 }
 
diff --git a/source/blender/editors/space_view3d/view3d_edit.c b/source/blender/editors/space_view3d/view3d_edit.c
index 17d467e593e..643e08ab405 100644
--- a/source/blender/editors/space_view3d/view3d_edit.c
+++ b/source/blender/editors/space_view3d/view3d_edit.c
@@ -441,11 +441,18 @@ static void viewops_data_create(bContext *C, wmOperator *op, const wmEvent *even
 		Object *ob = OBACT;
 
 		if (ob && (ob->mode & OB_MODE_ALL_PAINT) && (BKE_object_pose_armature_get(ob) == NULL)) {
-			/* transformation is disabled for painting modes, which will make it
-			 * so previous offset is used. This is annoying when you open file
-			 * saved with active object in painting mode
+			/* in case of sculpting use last average stroke position as a rotation
+			 * center, in other cases it's not clear what rotation center shall be
+			 * so just rotate around object origin
 			 */
-			copy_v3_v3(lastofs, ob->obmat[3]);
+			if (ob->mode & OB_MODE_SCULPT) {
+				float stroke[3];
+				ED_sculpt_get_average_stroke(ob, stroke);
+				copy_v3_v3(lastofs, stroke);
+			}
+			else {
+				copy_v3_v3(lastofs, ob->obmat[3]);
+			}
 		}
 		else {
 			/* If there's no selection, lastofs is unmodified and last value since static */