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, 7 insertions, 0 deletions

diff --git a/source/blender/editors/sculpt_paint/sculpt_intern.h b/source/blender/editors/sculpt_paint/sculpt_intern.h
index 41982a441ad..6cdaafb548c 100644
--- a/source/blender/editors/sculpt_paint/sculpt_intern.h
+++ b/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];