Clay Strips: Input pressure curve and new defaults

By squaring the pen pressure and disabling BRUSH_SPACE_ATTEN the brush
feels like it has a bigger strength range, wich makes it easier to
control when applying less pressure in order to smooth sculpted
surfaces.

Each brush should have a custom input pressure curve by default to get
an optimal behaviour and make all brushes consistent, but that is going
to take some time to get it right.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D6214

2 files changed, 19 insertions, 4 deletions

diff --git a/source/blender/editors/sculpt_paint/paint_cursor.c b/source/blender/editors/sculpt_paint/paint_cursor.c
index 385e37f7d22..b9af33e7ad6 100644
--- a/source/blender/editors/sculpt_paint/paint_cursor.c
+++ b/source/blender/editors/sculpt_paint/paint_cursor.c
@@ -1343,7 +1343,8 @@ static void paint_draw_cursor(bContext *C, int x, int y, void *UNUSED(unused))
 
     immUniformColor3fvAlpha(outline_col, outline_alpha);
 
-    if (ups->stroke_active && BKE_brush_use_size_pressure(scene, brush)) {
+    if (ups->stroke_active && BKE_brush_use_size_pressure(scene, brush) &&
+        mode != PAINT_MODE_SCULPT) {
       imm_draw_circle_wire_3d(
           pos, translation[0], translation[1], final_radius * ups->size_pressure_value, 40);
       /* outer at half alpha */
diff --git a/source/blender/editors/sculpt_paint/sculpt.c b/source/blender/editors/sculpt_paint/sculpt.c
index 89bc7912ccf..00d2f948c5f 100644
--- a/source/blender/editors/sculpt_paint/sculpt.c
+++ b/source/blender/editors/sculpt_paint/sculpt.c
@@ -1731,6 +1731,9 @@ static float brush_strength(const Sculpt *sd,
 
   float flip = dir * invert * pen_flip;
 
+  /* Pressure final value after being tweaked depending on the brush */
+  float final_pressure;
+
   switch (brush->sculpt_tool) {
     case SCULPT_TOOL_CLAY:
     case SCULPT_TOOL_DRAW:
@@ -1738,8 +1741,9 @@ static float brush_strength(const Sculpt *sd,
     case SCULPT_TOOL_LAYER:
       return alpha * flip * pressure * overlap * feather;
     case SCULPT_TOOL_CLAY_STRIPS:
-      /* Clay Strips needs extra strength to compensate for its default normal radius */
-      return alpha * flip * pressure * overlap * feather * 1.3f;
+      /* Clay Strips needs less strength to compensate the curve */
+      final_pressure = pressure * pressure * pressure;
+      return alpha * flip * final_pressure * overlap * feather * 0.3f;
 
     case SCULPT_TOOL_MASK:
       overlap = (1 + overlap) / 2;
@@ -6133,6 +6137,16 @@ static void sculpt_update_cache_invariants(
 #undef PIXEL_INPUT_THRESHHOLD
 }
 
+static float sculpt_brush_dynamic_size_get(Brush *brush, StrokeCache *cache, float initial_size)
+{
+  switch (brush->sculpt_tool) {
+    case SCULPT_TOOL_CLAY_STRIPS:
+      return max_ff(initial_size * 0.35f, initial_size * cache->pressure * cache->pressure);
+    default:
+      return initial_size * cache->pressure;
+  }
+}
+
 static void sculpt_update_brush_delta(UnifiedPaintSettings *ups, Object *ob, Brush *brush)
 {
   SculptSession *ss = ob->sculpt;
@@ -6331,7 +6345,7 @@ static void sculpt_update_cache_variants(bContext *C, Sculpt *sd, Object *ob, Po
 
   if (BKE_brush_use_size_pressure(scene, brush) &&
       paint_supports_dynamic_size(brush, PAINT_MODE_SCULPT)) {
-    cache->radius = cache->initial_radius * cache->pressure;
+    cache->radius = sculpt_brush_dynamic_size_get(brush, cache, cache->initial_radius);
   }
   else {
     cache->radius = cache->initial_radius;