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

1 files changed, 26 insertions, 0 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index c4c9db69dcd..6e99edcf682 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/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)) {