Fix T99644: Anchored brush mode fails for negative brushes

The stroke code now supports raycasting the original mesh.
This fixes anchored mode not working for negative brushes,
which might move the mesh out of the initial mouse cursor
position.

1 files changed, 20 insertions, 8 deletions

diff --git a/source/blender/editors/sculpt_paint/paint_stroke.c b/source/blender/editors/sculpt_paint/paint_stroke.c
index a4c942796d8..33a307376bb 100644
--- a/source/blender/editors/sculpt_paint/paint_stroke.c
+++ b/source/blender/editors/sculpt_paint/paint_stroke.c
@@ -122,6 +122,8 @@ typedef struct PaintStroke {
   StrokeUpdateStep update_step;
   StrokeRedraw redraw;
   StrokeDone done;
+
+  bool original; /* Raycast original mesh at start of stroke */
 } PaintStroke;
 
 /*** Cursors ***/
@@ -245,6 +247,11 @@ static bool paint_stroke_use_scene_spacing(Brush *brush, ePaintMode mode)
   return false;
 }
 
+static bool paint_tool_raycast_original(Brush *brush, ePaintMode mode)
+{
+  return brush->flag & BRUSH_ANCHORED;
+}
+
 static bool paint_tool_require_inbetween_mouse_events(Brush *brush, ePaintMode mode)
 {
   if (brush->flag & BRUSH_ANCHORED) {
@@ -394,7 +401,7 @@ static bool paint_brush_update(bContext *C,
       halfway[1] = dy * 0.5f + stroke->initial_mouse[1];
 
       if (stroke->get_location) {
-        if (stroke->get_location(C, r_location, halfway)) {
+        if (stroke->get_location(C, r_location, halfway, stroke->original)) {
           hit = true;
           location_sampled = true;
           location_success = true;
@@ -468,7 +475,7 @@ static bool paint_brush_update(bContext *C,
 
   if (!location_sampled) {
     if (stroke->get_location) {
-      if (stroke->get_location(C, r_location, mouse)) {
+      if (stroke->get_location(C, r_location, mouse, stroke->original)) {
         location_success = true;
         *r_location_is_set = true;
       }
@@ -554,7 +561,8 @@ static void paint_brush_stroke_add_step(
   if (paint_stroke_use_scene_spacing(brush, mode)) {
     float world_space_position[3];
 
-    if (SCULPT_stroke_get_location(C, world_space_position, stroke->last_mouse_position)) {
+    if (SCULPT_stroke_get_location(
+            C, world_space_position, stroke->last_mouse_position, stroke->original)) {
       copy_v3_v3(stroke->last_world_space_position, world_space_position);
       mul_m4_v3(stroke->vc.obact->obmat, stroke->last_world_space_position);
     }
@@ -816,7 +824,7 @@ static int paint_space_stroke(bContext *C,
 
   if (use_scene_spacing) {
     float world_space_position[3];
-    bool hit = SCULPT_stroke_get_location(C, world_space_position, final_mouse);
+    bool hit = SCULPT_stroke_get_location(C, world_space_position, final_mouse, stroke->original);
     mul_m4_v3(stroke->vc.obact->obmat, world_space_position);
     if (hit && stroke->stroke_over_mesh) {
       sub_v3_v3v3(d_world_space_position, world_space_position, stroke->last_world_space_position);
@@ -907,6 +915,8 @@ PaintStroke *paint_stroke_new(bContext *C,
   stroke->ups = ups;
   stroke->stroke_mode = RNA_enum_get(op->ptr, "mode");
 
+  stroke->original = paint_tool_raycast_original(br, BKE_paintmode_get_active_from_context(C));
+
   get_imapaint_zoom(C, &zoomx, &zoomy);
   stroke->zoom_2d = max_ff(zoomx, zoomy);
 
@@ -1202,8 +1212,10 @@ static void paint_line_strokes_spacing(bContext *C,
   copy_v2_v2(stroke->last_mouse_position, old_pos);
 
   if (use_scene_spacing) {
-    bool hit_old = SCULPT_stroke_get_location(C, world_space_position_old, old_pos);
-    bool hit_new = SCULPT_stroke_get_location(C, world_space_position_new, new_pos);
+    bool hit_old = SCULPT_stroke_get_location(
+        C, world_space_position_old, old_pos, stroke->original);
+    bool hit_new = SCULPT_stroke_get_location(
+        C, world_space_position_new, new_pos, stroke->original);
     mul_m4_v3(stroke->vc.obact->obmat, world_space_position_old);
     mul_m4_v3(stroke->vc.obact->obmat, world_space_position_new);
     if (hit_old && hit_new && stroke->stroke_over_mesh) {
@@ -1347,7 +1359,7 @@ static bool paint_stroke_curve_end(bContext *C, wmOperator *op, PaintStroke *str
 
           if (paint_stroke_use_scene_spacing(br, BKE_paintmode_get_active_from_context(C))) {
             stroke->stroke_over_mesh = SCULPT_stroke_get_location(
-                C, stroke->last_world_space_position, data + 2 * j);
+                C, stroke->last_world_space_position, data + 2 * j, stroke->original);
             mul_m4_v3(stroke->vc.obact->obmat, stroke->last_world_space_position);
           }
 
@@ -1479,7 +1491,7 @@ int paint_stroke_modal(bContext *C, wmOperator *op, const wmEvent *event, PaintS
     copy_v2_v2(stroke->last_mouse_position, sample_average.mouse);
     if (paint_stroke_use_scene_spacing(br, mode)) {
       stroke->stroke_over_mesh = SCULPT_stroke_get_location(
-          C, stroke->last_world_space_position, sample_average.mouse);
+          C, stroke->last_world_space_position, sample_average.mouse, stroke->original);
       mul_m4_v3(stroke->vc.obact->obmat, stroke->last_world_space_position);
     }
     stroke->stroke_started = stroke->test_start(C, op, sample_average.mouse);