Sculpt: Experimental Pen Tilt Support

This adds support for pen tilt in sculpt mode. For now, pen tilt is used
by tweaking the tilt strength property, which controls how much the pen
angle affects the sculpt normal. This is available in Draw, Draw Sharp,
Flatten, Fill, Scrape and Clay Strips brushes, but it can be enabled in
more tools later.

The purpose of this patch is to have a usable implementation of pen tilt
in a painting mode, so users can test and see in which hardware and
platforms this feature is supported and how well it works. If it works
ok, more tools and features that rely on pen tilt can be implemented,
like brushes that blend between two deformations depending on the angle.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D8893

release/scripts/startup/bl_ui/properties_paint_common.py

@@ -547,6 +547,10 @@ def brush_settings(layout, context, brush, popover=False):
         # normal_radius_factor
         layout.prop(brush, "normal_radius_factor", slider=True)
 
+        if context.preferences.experimental.use_sculpt_tools_tilt and capabilities.has_tilt:
+            layout.prop(brush, "tilt_strength_factor", slider=True)
+
+
         row = layout.row(align=True)
         row.prop(brush, "hardness", slider=True)
         row.prop(brush, "invert_hardness_pressure", text="")

release/scripts/startup/bl_ui/space_userpref.py

@@ -2187,6 +2187,7 @@ class USERPREF_PT_experimental_new_features(ExperimentalPanel, Panel):
                 ({"property": "use_sculpt_vertex_colors"}, "T71947"),
                 ({"property": "use_tools_missing_icons"}, "T80331"),
                 ({"property": "use_switch_object_operator"}, "T80402"),
+                ({"property": "use_sculpt_tools_tilt"}, "T00000"),
             ),
         )
 

source/blender/editors/sculpt_paint/paint_stroke.c

@@ -123,6 +123,10 @@ typedef struct PaintStroke {
   float zoom_2d;
   int pen_flip;
 
+  /* Tilt, as read from the event. */
+  float x_tilt;
+  float y_tilt;
+
   /* line constraint */
   bool constrain_line;
   float constrained_pos[2];
@@ -620,6 +624,8 @@ static void paint_brush_stroke_add_step(bContext *C,
     RNA_float_set_array(&itemptr, "mouse", mouse_out);
     RNA_boolean_set(&itemptr, "pen_flip", stroke->pen_flip);
     RNA_float_set(&itemptr, "pressure", pressure);
+    RNA_float_set(&itemptr, "x_tilt", stroke->x_tilt);
+    RNA_float_set(&itemptr, "y_tilt", stroke->y_tilt);
 
     stroke->update_step(C, stroke, &itemptr);
 
@@ -1383,6 +1389,12 @@ int paint_stroke_modal(bContext *C, wmOperator *op, const wmEvent *event)
   paint_stroke_add_sample(p, stroke, event->mval[0], event->mval[1], pressure);
   paint_stroke_sample_average(stroke, &sample_average);
 
+  /* Tilt. */
+  if (WM_event_is_tablet(event)) {
+    stroke->x_tilt = event->tablet.x_tilt;
+    stroke->y_tilt = event->tablet.y_tilt;
+  }
+
 #ifdef WITH_INPUT_NDOF
   /* let NDOF motion pass through to the 3D view so we can paint and rotate simultaneously!
    * this isn't perfect... even when an extra MOUSEMOVE is spoofed, the stroke discards it

source/blender/editors/sculpt_paint/sculpt.c

@@ -2784,6 +2784,20 @@ static void calc_brush_local_mat(const Brush *brush, Object *ob, float local_mat
   invert_m4_m4(local_mat, tmat);
 }
 
+#define SCULPT_TILT_SENSITIVITY 0.7f
+void SCULPT_tilt_apply_to_normal(float r_normal[3], StrokeCache *cache, const float tilt_strength)
+{
+  if (!U.experimental.use_sculpt_tools_tilt) {
+    return;
+  }
+  const float rot_max = M_PI_2 * tilt_strength * SCULPT_TILT_SENSITIVITY;
+  mul_v3_mat3_m4v3(r_normal, cache->vc->obact->obmat, r_normal);
+  rotate_v3_v3v3fl(r_normal, r_normal, cache->vc->rv3d->viewinv[0], cache->y_tilt * rot_max);
+  rotate_v3_v3v3fl(r_normal, r_normal, cache->vc->rv3d->viewinv[1], cache->x_tilt * rot_max);
+  mul_v3_mat3_m4v3(r_normal, cache->vc->obact->imat, r_normal);
+  normalize_v3(r_normal);
+}
+
 static void update_brush_local_mat(Sculpt *sd, Object *ob)
 {
   StrokeCache *cache = ob->sculpt->cache;
@@ -3094,6 +3108,7 @@ static void do_draw_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode)
 
   /* Offset with as much as possible factored in already. */
   mul_v3_v3fl(offset, ss->cache->sculpt_normal_symm, ss->cache->radius);
+  SCULPT_tilt_apply_to_normal(offset, ss->cache, brush->tilt_strength_factor);
   mul_v3_v3(offset, ss->cache->scale);
   mul_v3_fl(offset, bstrength);
 
@@ -3171,6 +3186,7 @@ static void do_draw_sharp_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int to
 
   /* Offset with as much as possible factored in already. */
   mul_v3_v3fl(offset, ss->cache->sculpt_normal_symm, ss->cache->radius);
+  SCULPT_tilt_apply_to_normal(offset, ss->cache, brush->tilt_strength_factor);
   mul_v3_v3(offset, ss->cache->scale);
   mul_v3_fl(offset, bstrength);
 
@@ -4693,6 +4709,8 @@ static void do_flatten_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totno
 
   SCULPT_calc_brush_plane(sd, ob, nodes, totnode, area_no, area_co);
 
+  SCULPT_tilt_apply_to_normal(area_no, ss->cache, brush->tilt_strength_factor);
+
   displace = radius * offset;
 
   mul_v3_v3v3(temp, area_no, ss->cache->scale);
@@ -4977,6 +4995,7 @@ static void do_clay_strips_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int t
   float tmat[4][4];
 
   SCULPT_calc_brush_plane(sd, ob, nodes, totnode, area_no_sp, area_co);
+  SCULPT_tilt_apply_to_normal(area_no_sp, ss->cache, brush->tilt_strength_factor);
 
   if (brush->sculpt_plane != SCULPT_DISP_DIR_AREA || (brush->flag & BRUSH_ORIGINAL_NORMAL)) {
     SCULPT_calc_area_normal(sd, ob, nodes, totnode, area_no);
@@ -5120,6 +5139,8 @@ static void do_fill_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnode)
 
   SCULPT_calc_brush_plane(sd, ob, nodes, totnode, area_no, area_co);
 
+  SCULPT_tilt_apply_to_normal(area_no, ss->cache, brush->tilt_strength_factor);
+
   displace = radius * offset;
 
   mul_v3_v3v3(temp, area_no, ss->cache->scale);
@@ -5213,6 +5234,8 @@ static void do_scrape_brush(Sculpt *sd, Object *ob, PBVHNode **nodes, int totnod
 
   SCULPT_calc_brush_plane(sd, ob, nodes, totnode, area_no, area_co);
 
+  SCULPT_tilt_apply_to_normal(area_no, ss->cache, brush->tilt_strength_factor);
+
   displace = -radius * offset;
 
   mul_v3_v3v3(temp, area_no, ss->cache->scale);
@@ -6935,6 +6958,9 @@ static void sculpt_update_cache_variants(bContext *C, Sculpt *sd, Object *ob, Po
     cache->pressure = RNA_float_get(ptr, "pressure");
   }
 
+  cache->x_tilt = RNA_float_get(ptr, "x_tilt");
+  cache->y_tilt = RNA_float_get(ptr, "y_tilt");
+
   /* Truly temporary data that isn't stored in properties. */
   if (SCULPT_stroke_is_first_brush_step_of_symmetry_pass(ss->cache)) {
     if (!BKE_brush_use_locked_size(scene, brush)) {

source/blender/editors/sculpt_paint/sculpt_intern.h

@@ -799,6 +799,11 @@ float SCULPT_brush_strength_factor(struct SculptSession *ss,
                                    const int vertex_index,
                                    const int thread_id);
 
+/* Tilts a normal by the x and y tilt values using the view axis. */
+void SCULPT_tilt_apply_to_normal(float r_normal[3],
+                                 struct StrokeCache *cache,
+                                 const float tilt_strength);
+
 /* just for vertex paint. */
 bool SCULPT_pbvh_calc_area_normal(const struct Brush *brush,
                                   Object *ob,
@@ -852,6 +857,8 @@ typedef struct StrokeCache {
   float mouse[2];
   float bstrength;
   float normal_weight; /* from brush (with optional override) */
+  float x_tilt;
+  float y_tilt;
 
   float (*prev_colors)[4];
 

source/blender/makesdna/DNA_brush_types.h

@@ -568,10 +568,12 @@ typedef struct Brush {
   char gpencil_sculpt_tool;
   /** Active grease pencil weight tool. */
   char gpencil_weight_tool;
-  char _pad1[2];
+  char _pad1[6];
 
   float autosmooth_factor;
 
+  float tilt_strength_factor;
+
   float topology_rake_factor;
 
   float crease_pinch_factor;

source/blender/makesdna/DNA_userdef_types.h

@@ -635,7 +635,9 @@ typedef struct UserDef_Experimental {
   char use_sculpt_vertex_colors;
   char use_tools_missing_icons;
   char use_switch_object_operator;
-  char _pad[7];
+  char use_sculpt_tools_tilt;
+  char _pad[6];
+  /** `makesdna` does not allow empty structs. */
 } UserDef_Experimental;
 
 #define USER_EXPERIMENTAL_TEST(userdef, member) \

source/blender/makesrna/intern/rna_brush.c

@@ -557,6 +557,19 @@ static bool rna_BrushCapabilitiesSculpt_has_gravity_get(PointerRNA *ptr)
   return !ELEM(br->sculpt_tool, SCULPT_TOOL_MASK, SCULPT_TOOL_SMOOTH);
 }
 
+static bool rna_BrushCapabilitiesSculpt_has_tilt_get(PointerRNA *ptr)
+{
+  Brush *br = (Brush *)ptr->data;
+  return ELEM(br->sculpt_tool,
+              SCULPT_TOOL_DRAW,
+              SCULPT_TOOL_DRAW_SHARP,
+              SCULPT_TOOL_FLATTEN,
+              SCULPT_TOOL_FILL,
+              SCULPT_TOOL_SCRAPE,
+              SCULPT_TOOL_CLAY_STRIPS,
+              SCULPT_TOOL_CLAY_THUMB);
+}
+
 static bool rna_TextureCapabilities_has_texture_angle_source_get(PointerRNA *ptr)
 {
   MTex *mtex = (MTex *)ptr->data;
@@ -1137,6 +1150,7 @@ static void rna_def_sculpt_capabilities(BlenderRNA *brna)
   SCULPT_TOOL_CAPABILITY(has_strength_pressure, "Has Strength Pressure");
   SCULPT_TOOL_CAPABILITY(has_direction, "Has Direction");
   SCULPT_TOOL_CAPABILITY(has_gravity, "Has Gravity");
+  SCULPT_TOOL_CAPABILITY(has_tilt, "Has Tilt");
 
 #  undef SCULPT_CAPABILITY
 }
@@ -2796,6 +2810,15 @@ static void rna_def_brush(BlenderRNA *brna)
                            "Best used on low-poly meshes as it has a performance impact");
   RNA_def_property_update(prop, 0, "rna_Brush_update");
 
+  prop = RNA_def_property(srna, "tilt_strength_factor", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_float_sdna(prop, NULL, "tilt_strength_factor");
+  RNA_def_property_float_default(prop, 0);
+  RNA_def_property_range(prop, 0.0f, 1.0f);
+  RNA_def_property_ui_range(prop, 0.0f, 1.0f, 0.001, 3);
+  RNA_def_property_ui_text(
+      prop, "Tilt Strength", "How much the tilt of the pen will affect the brush");
+  RNA_def_property_update(prop, 0, "rna_Brush_update");
+
   prop = RNA_def_property(srna, "normal_radius_factor", PROP_FLOAT, PROP_FACTOR);
   RNA_def_property_float_sdna(prop, NULL, "normal_radius_factor");
   RNA_def_property_range(prop, 0.0f, 2.0f);
@@ -3417,6 +3440,16 @@ static void rna_def_operator_stroke_element(BlenderRNA *brna)
   RNA_def_property_flag(prop, PROP_IDPROPERTY);
   RNA_def_property_ui_text(prop, "Flip", "");
 
+  prop = RNA_def_property(srna, "x_tilt", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_flag(prop, PROP_IDPROPERTY);
+  RNA_def_property_range(prop, -1.0f, 1.0f);
+  RNA_def_property_ui_text(prop, "Tilt X", "");
+
+  prop = RNA_def_property(srna, "y_tilt", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_flag(prop, PROP_IDPROPERTY);
+  RNA_def_property_range(prop, -1.0f, 1.0f);
+  RNA_def_property_ui_text(prop, "Tilt Y", "");
+
   /* used in uv painting */
   prop = RNA_def_property(srna, "time", PROP_FLOAT, PROP_UNSIGNED);
   RNA_def_property_flag(prop, PROP_IDPROPERTY);

source/blender/makesrna/intern/rna_userdef.c

@@ -6178,6 +6178,11 @@ static void rna_def_userdef_experimental(BlenderRNA *brna)
   prop = RNA_def_property(srna, "use_tools_missing_icons", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "use_tools_missing_icons", 1);
   RNA_def_property_ui_text(prop, "Tools with Missing Icons", "Show tools with missing icons");
+
+  prop = RNA_def_property(srna, "use_sculpt_tools_tilt", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "use_sculpt_tools_tilt", 1);
+  RNA_def_property_ui_text(
+      prop, "Sculpt Mode Tilt Support", "Support for pen tablet tilt events in Sculpt Mode");
 }
 
 static void rna_def_userdef_addon_collection(BlenderRNA *brna, PropertyRNA *cprop)