Curves: Port tangent and normal calculation to the new data-block

Port the "Normal" and "Curve Tangent" nodes to the new curves data-block
to avoid the conversion to `CurveEval`. This should make them faster by
avoiding all that copying, but otherwise nothing else has changed.

This also includes a fix to move the normal mode as a built-in curve
attribute when converting to and from `CurveEval`. The attribute is
needed because the option is used implicitly in many nodes currently.

Differential Revision: https://developer.blender.org/D14609

1 files changed, 42 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_curves.hh b/source/blender/blenkernel/BKE_curves.hh
index c4edeae99a4..9fd023edcf2 100644
--- a/source/blender/blenkernel/BKE_curves.hh
+++ b/source/blender/blenkernel/BKE_curves.hh
@@ -158,6 +158,9 @@ class CurvesGeometry : public ::CurvesGeometry {
   /** Return the number of curves with each type. */
   std::array<int, CURVE_TYPES_NUM> count_curve_types() const;
 
+  /** Return true if all of the curves have the provided type. */
+  bool is_single_type(CurveType type) const;
+
   Span<float3> positions() const;
   MutableSpan<float3> positions_for_write();
 
@@ -175,6 +178,13 @@ class CurvesGeometry : public ::CurvesGeometry {
   MutableSpan<int> resolution_for_write();
 
   /**
+   * Which method to use for calculating the normals of evaluated points (#NormalMode).
+   * Call #tag_normals_changed after changes.
+   */
+  VArray<int8_t> normal_mode() const;
+  MutableSpan<int8_t> normal_mode_for_write();
+
+  /**
    * Handle types for Bezier control points. Call #tag_topology_changed after changes.
    */
   VArray<int8_t> handle_types_left() const;
@@ -280,6 +290,8 @@ class CurvesGeometry : public ::CurvesGeometry {
   Span<int> bezier_evaluated_offsets_for_curve(int curve_index) const;
 
   Span<float3> evaluated_positions() const;
+  Span<float3> evaluated_tangents() const;
+  Span<float3> evaluated_normals() const;
 
   /**
    * Return a cache of accumulated lengths along the curve. Each item is the length of the
@@ -379,6 +391,31 @@ inline float3 decode_surface_bary_coord(const float2 &v)
   return {v.x, v.y, 1.0f - v.x - v.y};
 }
 
+namespace poly {
+
+/**
+ * Calculate the direction at every point, defined as the normalized average of the two neighboring
+ * segments (and if non-cyclic, the direction of the first and last segments). This is different
+ * than evaluating the derivative of the basis functions for curve types like NURBS, Bezier, or
+ * Catmull Rom, though the results may be similar.
+ */
+void calculate_tangents(Span<float3> positions, bool is_cyclic, MutableSpan<float3> tangents);
+
+/**
+ * Calculate directions perpendicular to the tangent at every point by rotating an arbitrary
+ * starting vector by the same rotation of each tangent. If the curve is cylic, propagate a
+ * correction through the entire to make sure the first and last normal align.
+ */
+void calculate_normals_minimum(Span<float3> tangents, bool cyclic, MutableSpan<float3> normals);
+
+/**
+ * Calculate a vector perpendicular to every tangent on the X-Y plane (unless the tangent is
+ * vertical, in that case use the X direction).
+ */
+void calculate_normals_z_up(Span<float3> tangents, MutableSpan<float3> normals);
+
+}  // namespace poly
+
 namespace bezier {
 
 /**
@@ -586,6 +623,11 @@ inline IndexRange CurvesGeometry::curves_range() const
   return IndexRange(this->curves_num());
 }
 
+inline bool CurvesGeometry::is_single_type(const CurveType type) const
+{
+  return this->count_curve_types()[type] == this->curves_num();
+}
+
 inline IndexRange CurvesGeometry::points_for_curve(const int index) const
 {
   /* Offsets are not allocated when there are no curves. */