Curves: Add soft selection in sculpt mode

This commit adds a float selection to curve control points or curves,
a sculpt tool to paint the selection, and uses the selection influence
in the existing sculpt brushes.

The selection is the inverse of the "mask" from mesh sculpt mode
currently. That change is described in more detail here: T97903

Since some sculpt tools are really "per curve" tools, they use the
average point selection of all of their points. The delete brush
considers a curve selected if any of its points have a non-zero
selection.

There is a new option to choose the selection domain, which affects how
painting the selection works. You can also turn the selection off by
clicking on the active domain.

Sculpt brushes can be faster when the selection is small, because
finding selected curves or points is generally faster than the
existing brush intersection and distance checks.

The main limitation currently is that we can't see the selection in the
viewport by default. For now, to see the selection one has to add a
simple material to the curves object as shown in the differential
revision. And one has to switch to Material Preview in the 3d view.

Differential Revision: https://developer.blender.org/D14934

1 files changed, 14 insertions, 2 deletions

diff --git a/source/blender/editors/sculpt_paint/curves_sculpt_grow_shrink.cc b/source/blender/editors/sculpt_paint/curves_sculpt_grow_shrink.cc
index 25eb8041f4c..d87828e7437 100644
--- a/source/blender/editors/sculpt_paint/curves_sculpt_grow_shrink.cc
+++ b/source/blender/editors/sculpt_paint/curves_sculpt_grow_shrink.cc
@@ -280,6 +280,10 @@ struct CurvesEffectOperationExecutor {
   Curves *curves_id_ = nullptr;
   CurvesGeometry *curves_ = nullptr;
 
+  VArray<float> curve_selection_factors_;
+  Vector<int64_t> selected_curve_indices_;
+  IndexMask curve_selection_;
+
   const Brush *brush_ = nullptr;
   float brush_radius_base_re_;
   float brush_radius_factor_;
@@ -318,6 +322,9 @@ struct CurvesEffectOperationExecutor {
       return;
     }
 
+    curve_selection_factors_ = get_curves_selection(*curves_id_);
+    curve_selection_ = retrieve_selected_curves(*curves_id_, selected_curve_indices_);
+
     const CurvesSculpt &curves_sculpt = *scene_->toolsettings->curves_sculpt;
     brush_ = BKE_paint_brush_for_read(&curves_sculpt.paint);
     brush_strength_ = brush_strength_get(*scene_, *brush_, stroke_extension);
@@ -396,6 +403,8 @@ struct CurvesEffectOperationExecutor {
       for (const int curve_i : curves_range) {
         const IndexRange points = curves_->points_for_curve(curve_i);
 
+        const float curve_selection_factor = curve_selection_factors_[curve_i];
+
         float max_move_distance_cu = 0.0f;
         for (const float4x4 &brush_transform_inv : symmetry_brush_transforms_inv) {
           for (const int segment_i : points.drop_back(1)) {
@@ -426,7 +435,7 @@ struct CurvesEffectOperationExecutor {
             const float dist_to_brush_re = std::sqrt(dist_to_brush_sq_re);
             const float radius_falloff = BKE_brush_curve_strength(
                 brush_, dist_to_brush_re, brush_radius_re);
-            const float weight = brush_strength_ * radius_falloff;
+            const float weight = brush_strength_ * radius_falloff * curve_selection_factor;
 
             const float3 closest_on_segment_cu = math::interpolate(
                 p1_cu, p2_cu, lambda_on_segment);
@@ -491,6 +500,9 @@ struct CurvesEffectOperationExecutor {
         const IndexRange points = curves_->points_for_curve(curve_i);
 
         float max_move_distance_cu = 0.0f;
+
+        const float curve_selection_factor = curve_selection_factors_[curve_i];
+
         for (const float4x4 &brush_transform : symmetry_brush_transforms) {
           const float3 brush_pos_start_transformed_cu = brush_transform * brush_pos_start_cu;
           const float3 brush_pos_end_transformed_cu = brush_transform * brush_pos_end_cu;
@@ -517,7 +529,7 @@ struct CurvesEffectOperationExecutor {
             const float dist_to_brush_cu = std::sqrt(dist_to_brush_sq_cu);
             const float radius_falloff = BKE_brush_curve_strength(
                 brush_, dist_to_brush_cu, brush_radius_cu);
-            const float weight = brush_strength_ * radius_falloff;
+            const float weight = brush_strength_ * radius_falloff * curve_selection_factor;
 
             const float move_distance_cu = weight * brush_pos_diff_length_cu;
             max_move_distance_cu = std::max(max_move_distance_cu, move_distance_cu);