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

7 files changed, 448 insertions, 104 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. */
diff --git a/source/blender/blenkernel/CMakeLists.txt b/source/blender/blenkernel/CMakeLists.txt
index 61131cff06d..aca8cdf916e 100644
--- a/source/blender/blenkernel/CMakeLists.txt
+++ b/source/blender/blenkernel/CMakeLists.txt
@@ -112,6 +112,7 @@ set(SRC
   intern/curve_deform.c
   intern/curve_eval.cc
   intern/curve_nurbs.cc
+  intern/curve_poly.cc
   intern/curve_to_mesh_convert.cc
   intern/curveprofile.cc
   intern/curves.cc
diff --git a/source/blender/blenkernel/intern/curve_eval.cc b/source/blender/blenkernel/intern/curve_eval.cc
index 9b1fd510fa8..6e09d1e8f10 100644
--- a/source/blender/blenkernel/intern/curve_eval.cc
+++ b/source/blender/blenkernel/intern/curve_eval.cc
@@ -381,6 +381,7 @@ std::unique_ptr<CurveEval> curves_to_curve_eval(const Curves &curves)
       curves.geometry);
 
   VArray<int> resolution = geometry.resolution();
+  VArray<int8_t> normal_mode = geometry.normal_mode();
 
   VArray_Span<float> nurbs_weights{
       src_component.attribute_get_for_read<float>("nurbs_weight", ATTR_DOMAIN_POINT, 0.0f)};
@@ -436,6 +437,7 @@ std::unique_ptr<CurveEval> curves_to_curve_eval(const Curves &curves)
     spline->positions().fill(float3(0));
     spline->tilts().fill(0.0f);
     spline->radii().fill(1.0f);
+    spline->normal_mode = static_cast<NormalMode>(normal_mode[curve_index]);
     curve_eval->add_spline(std::move(spline));
   }
 
@@ -448,6 +450,7 @@ std::unique_ptr<CurveEval> curves_to_curve_eval(const Curves &curves)
                                      dst_component,
                                      {"curve_type",
                                       "resolution",
+                                      "normal_mode",
                                       "nurbs_weight",
                                       "nurbs_order",
                                       "knots_mode",
@@ -468,6 +471,8 @@ Curves *curve_eval_to_curves(const CurveEval &curve_eval)
   geometry.offsets_for_write().copy_from(curve_eval.control_point_offsets());
   MutableSpan<int8_t> curve_types = geometry.curve_types_for_write();
 
+  OutputAttribute_Typed<int8_t> normal_mode =
+      dst_component.attribute_try_get_for_output_only<int8_t>("normal_mode", ATTR_DOMAIN_CURVE);
   OutputAttribute_Typed<float> nurbs_weight;
   OutputAttribute_Typed<int> nurbs_order;
   OutputAttribute_Typed<int8_t> nurbs_knots_mode;
@@ -491,7 +496,7 @@ Curves *curve_eval_to_curves(const CurveEval &curve_eval)
   for (const int curve_index : curve_eval.splines().index_range()) {
     const Spline &spline = *curve_eval.splines()[curve_index];
     curve_types[curve_index] = curve_eval.splines()[curve_index]->type();
-
+    normal_mode.as_span()[curve_index] = curve_eval.splines()[curve_index]->normal_mode;
     const IndexRange point_range = geometry.points_for_curve(curve_index);
 
     switch (spline.type()) {
@@ -517,6 +522,7 @@ Curves *curve_eval_to_curves(const CurveEval &curve_eval)
     }
   }
 
+  normal_mode.save();
   nurbs_weight.save();
   nurbs_order.save();
   nurbs_knots_mode.save();
diff --git a/source/blender/blenkernel/intern/curve_poly.cc b/source/blender/blenkernel/intern/curve_poly.cc
new file mode 100644
index 00000000000..b0ed62d38dd
--- /dev/null
+++ b/source/blender/blenkernel/intern/curve_poly.cc
@@ -0,0 +1,154 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include <algorithm>
+
+#include "BLI_math_vector.h"
+#include "BLI_math_vector.hh"
+
+#include "BKE_curves.hh"
+
+namespace blender::bke::curves::poly {
+
+static float3 direction_bisect(const float3 &prev, const float3 &middle, const float3 &next)
+{
+  const float3 dir_prev = math::normalize(middle - prev);
+  const float3 dir_next = math::normalize(next - middle);
+
+  const float3 result = math::normalize(dir_prev + dir_next);
+  if (UNLIKELY(math::is_zero(result))) {
+    return float3(0.0f, 0.0f, 1.0f);
+  }
+  return result;
+}
+
+void calculate_tangents(const Span<float3> positions,
+                        const bool is_cyclic,
+                        MutableSpan<float3> tangents)
+{
+  BLI_assert(positions.size() == tangents.size());
+
+  if (positions.size() == 1) {
+    tangents.first() = float3(0.0f, 0.0f, 1.0f);
+    return;
+  }
+
+  for (const int i : IndexRange(1, positions.size() - 2)) {
+    tangents[i] = direction_bisect(positions[i - 1], positions[i], positions[i + 1]);
+  }
+
+  if (is_cyclic) {
+    const float3 &second_to_last = positions[positions.size() - 2];
+    const float3 &last = positions.last();
+    const float3 &first = positions.first();
+    const float3 &second = positions[1];
+    tangents.first() = direction_bisect(last, first, second);
+    tangents.last() = direction_bisect(second_to_last, last, first);
+  }
+  else {
+    tangents.first() = math::normalize(positions[1] - positions.first());
+    tangents.last() = math::normalize(positions.last() - positions[positions.size() - 2]);
+  }
+}
+
+static float3 rotate_direction_around_axis(const float3 &direction,
+                                           const float3 &axis,
+                                           const float angle)
+{
+  BLI_ASSERT_UNIT_V3(direction);
+  BLI_ASSERT_UNIT_V3(axis);
+
+  const float3 axis_scaled = axis * math::dot(direction, axis);
+  const float3 diff = direction - axis_scaled;
+  const float3 cross = math::cross(axis, diff);
+
+  return axis_scaled + diff * std::cos(angle) + cross * std::sin(angle);
+}
+
+void calculate_normals_z_up(const Span<float3> tangents, MutableSpan<float3> normals)
+{
+  BLI_assert(normals.size() == tangents.size());
+
+  /* Same as in `vec_to_quat`. */
+  const float epsilon = 1e-4f;
+  for (const int i : normals.index_range()) {
+    const float3 &tangent = tangents[i];
+    if (std::abs(tangent.x) + std::abs(tangent.y) < epsilon) {
+      normals[i] = {1.0f, 0.0f, 0.0f};
+    }
+    else {
+      normals[i] = math::normalize(float3(tangent.y, -tangent.x, 0.0f));
+    }
+  }
+}
+
+/**
+ * Rotate the last normal in the same way the tangent has been rotated.
+ */
+static float3 calculate_next_normal(const float3 &last_normal,
+                                    const float3 &last_tangent,
+                                    const float3 &current_tangent)
+{
+  if (math::is_zero(last_tangent) || math::is_zero(current_tangent)) {
+    return last_normal;
+  }
+  const float angle = angle_normalized_v3v3(last_tangent, current_tangent);
+  if (angle != 0.0) {
+    const float3 axis = math::normalize(math::cross(last_tangent, current_tangent));
+    return rotate_direction_around_axis(last_normal, axis, angle);
+  }
+  return last_normal;
+}
+
+void calculate_normals_minimum(const Span<float3> tangents,
+                               const bool cyclic,
+                               MutableSpan<float3> normals)
+{
+  BLI_assert(normals.size() == tangents.size());
+
+  if (normals.is_empty()) {
+    return;
+  }
+
+  const float epsilon = 1e-4f;
+
+  /* Set initial normal. */
+  const float3 &first_tangent = tangents.first();
+  if (fabs(first_tangent.x) + fabs(first_tangent.y) < epsilon) {
+    normals.first() = {1.0f, 0.0f, 0.0f};
+  }
+  else {
+    normals.first() = math::normalize(float3(first_tangent.y, -first_tangent.x, 0.0f));
+  }
+
+  /* Forward normal with minimum twist along the entire spline. */
+  for (const int i : IndexRange(1, normals.size() - 1)) {
+    normals[i] = calculate_next_normal(normals[i - 1], tangents[i - 1], tangents[i]);
+  }
+
+  if (!cyclic) {
+    return;
+  }
+
+  /* Compute how much the first normal deviates from the normal that has been forwarded along the
+   * entire cyclic spline. */
+  const float3 uncorrected_last_normal = calculate_next_normal(
+      normals.last(), tangents.last(), tangents.first());
+  float correction_angle = angle_signed_on_axis_v3v3_v3(
+      normals.first(), uncorrected_last_normal, tangents.first());
+  if (correction_angle > M_PI) {
+    correction_angle = correction_angle - 2 * M_PI;
+  }
+
+  /* Gradually apply correction by rotating all normals slightly. */
+  const float angle_step = correction_angle / normals.size();
+  for (const int i : normals.index_range()) {
+    const float angle = angle_step * i;
+    normals[i] = rotate_direction_around_axis(normals[i], tangents[i], angle);
+  }
+}
+
+}  // namespace blender::bke::curves::poly
diff --git a/source/blender/blenkernel/intern/curves_geometry.cc b/source/blender/blenkernel/intern/curves_geometry.cc
index cbf2c910771..5c89dfd4df5 100644
--- a/source/blender/blenkernel/intern/curves_geometry.cc
+++ b/source/blender/blenkernel/intern/curves_geometry.cc
@@ -25,6 +25,7 @@ static const std::string ATTR_RADIUS = "radius";
 static const std::string ATTR_CURVE_TYPE = "curve_type";
 static const std::string ATTR_CYCLIC = "cyclic";
 static const std::string ATTR_RESOLUTION = "resolution";
+static const std::string ATTR_NORMAL_MODE = "normal_mode";
 static const std::string ATTR_HANDLE_TYPE_LEFT = "handle_type_left";
 static const std::string ATTR_HANDLE_TYPE_RIGHT = "handle_type_right";
 static const std::string ATTR_HANDLE_POSITION_LEFT = "handle_left";
@@ -320,6 +321,15 @@ MutableSpan<int> CurvesGeometry::resolution_for_write()
   return get_mutable_attribute<int>(*this, ATTR_DOMAIN_CURVE, ATTR_RESOLUTION, 12);
 }
 
+VArray<int8_t> CurvesGeometry::normal_mode() const
+{
+  return get_varray_attribute<int8_t>(*this, ATTR_DOMAIN_CURVE, ATTR_NORMAL_MODE, 0);
+}
+MutableSpan<int8_t> CurvesGeometry::normal_mode_for_write()
+{
+  return get_mutable_attribute<int8_t>(*this, ATTR_DOMAIN_CURVE, ATTR_NORMAL_MODE);
+}
+
 VArray<int8_t> CurvesGeometry::handle_types_left() const
 {
   return get_varray_attribute<int8_t>(*this, ATTR_DOMAIN_POINT, ATTR_HANDLE_TYPE_LEFT, 0);
@@ -638,6 +648,113 @@ Span<float3> CurvesGeometry::evaluated_positions() const
   return this->runtime->evaluated_position_cache;
 }
 
+Span<float3> CurvesGeometry::evaluated_tangents() const
+{
+  if (!this->runtime->tangent_cache_dirty) {
+    return this->runtime->evaluated_tangent_cache;
+  }
+
+  /* A double checked lock. */
+  std::scoped_lock lock{this->runtime->tangent_cache_mutex};
+  if (!this->runtime->tangent_cache_dirty) {
+    return this->runtime->evaluated_tangent_cache;
+  }
+
+  threading::isolate_task([&]() {
+    const Span<float3> evaluated_positions = this->evaluated_positions();
+    const VArray<bool> cyclic = this->cyclic();
+
+    this->runtime->evaluated_tangent_cache.resize(this->evaluated_points_num());
+    MutableSpan<float3> tangents = this->runtime->evaluated_tangent_cache;
+
+    threading::parallel_for(this->curves_range(), 128, [&](IndexRange curves_range) {
+      for (const int curve_index : curves_range) {
+        const IndexRange evaluated_points = this->evaluated_points_for_curve(curve_index);
+        if (UNLIKELY(evaluated_points.is_empty())) {
+          continue;
+        }
+        curves::poly::calculate_tangents(evaluated_positions.slice(evaluated_points),
+                                         cyclic[curve_index],
+                                         tangents.slice(evaluated_points));
+      }
+    });
+
+    /* Correct the first and last tangents of Bezier curves so that they align with the inner
+     * handles. This is a separate loop to avoid the cost when Bezier type curves are not used. */
+    Vector<int64_t> bezier_indices;
+    const IndexMask bezier_mask = this->indices_for_curve_type(CURVE_TYPE_BEZIER, bezier_indices);
+    if (!bezier_mask.is_empty()) {
+      const Span<float3> positions = this->positions();
+      const Span<float3> handles_left = this->handle_positions_left();
+      const Span<float3> handles_right = this->handle_positions_right();
+
+      threading::parallel_for(bezier_mask.index_range(), 1024, [&](IndexRange range) {
+        for (const int curve_index : bezier_mask.slice(range)) {
+          const IndexRange points = this->points_for_curve(curve_index);
+          const IndexRange evaluated_points = this->evaluated_points_for_curve(curve_index);
+
+          if (handles_right[points.first()] != positions[points.first()]) {
+            tangents[evaluated_points.first()] = math::normalize(handles_right[points.first()] -
+                                                                 positions[points.first()]);
+          }
+          if (handles_left[points.last()] != positions[points.last()]) {
+            tangents[evaluated_points.last()] = math::normalize(positions[points.last()] -
+                                                                handles_left[points.last()]);
+          }
+        }
+      });
+    }
+  });
+
+  this->runtime->tangent_cache_dirty = false;
+  return this->runtime->evaluated_tangent_cache;
+}
+
+Span<float3> CurvesGeometry::evaluated_normals() const
+{
+  if (!this->runtime->normal_cache_dirty) {
+    return this->runtime->evaluated_normal_cache;
+  }
+
+  /* A double checked lock. */
+  std::scoped_lock lock{this->runtime->normal_cache_mutex};
+  if (!this->runtime->normal_cache_dirty) {
+    return this->runtime->evaluated_normal_cache;
+  }
+
+  threading::isolate_task([&]() {
+    const Span<float3> evaluated_tangents = this->evaluated_tangents();
+    const VArray<bool> cyclic = this->cyclic();
+    const VArray<int8_t> normal_mode = this->normal_mode();
+
+    this->runtime->evaluated_normal_cache.resize(this->evaluated_points_num());
+    MutableSpan<float3> evaluated_normals = this->runtime->evaluated_normal_cache;
+
+    threading::parallel_for(this->curves_range(), 128, [&](IndexRange curves_range) {
+      for (const int curve_index : curves_range) {
+        const IndexRange evaluated_points = this->evaluated_points_for_curve(curve_index);
+        if (UNLIKELY(evaluated_points.is_empty())) {
+          continue;
+        }
+        switch (normal_mode[curve_index]) {
+          case NORMAL_MODE_Z_UP:
+            curves::poly::calculate_normals_z_up(evaluated_tangents.slice(evaluated_points),
+                                                 evaluated_normals.slice(evaluated_points));
+            break;
+          case NORMAL_MODE_MINIMUM_TWIST:
+            curves::poly::calculate_normals_minimum(evaluated_tangents.slice(evaluated_points),
+                                                    cyclic[curve_index],
+                                                    evaluated_normals.slice(evaluated_points));
+            break;
+        }
+      }
+    });
+  });
+
+  this->runtime->normal_cache_dirty = false;
+  return this->runtime->evaluated_normal_cache;
+}
+
 void CurvesGeometry::interpolate_to_evaluated(const int curve_index,
                                               const GSpan src,
                                               GMutableSpan dst) const
diff --git a/source/blender/blenkernel/intern/geometry_component_curves.cc b/source/blender/blenkernel/intern/geometry_component_curves.cc
index de986fec951..0bcab0aae7a 100644
--- a/source/blender/blenkernel/intern/geometry_component_curves.cc
+++ b/source/blender/blenkernel/intern/geometry_component_curves.cc
@@ -141,81 +141,97 @@ const Curve *CurveComponent::get_curve_for_render() const
 
 namespace blender::bke {
 
-static void calculate_bezier_normals(const BezierSpline &spline, MutableSpan<float3> normals)
+static Array<float3> curve_normal_point_domain(const bke::CurvesGeometry &curves)
 {
-  Span<int> offsets = spline.control_point_offsets();
-  Span<float3> evaluated_normals = spline.evaluated_normals();
-  for (const int i : IndexRange(spline.size())) {
-    normals[i] = evaluated_normals[offsets[i]];
-  }
-}
+  const VArray<int8_t> types = curves.curve_types();
+  const VArray<int> resolutions = curves.resolution();
+  const VArray<bool> curves_cyclic = curves.cyclic();
 
-static void calculate_poly_normals(const PolySpline &spline, MutableSpan<float3> normals)
-{
-  normals.copy_from(spline.evaluated_normals());
-}
+  const Span<float3> positions = curves.positions();
+  const VArray<int8_t> normal_modes = curves.normal_mode();
 
-/**
- * Because NURBS control points are not necessarily on the path, the normal at the control points
- * is not well defined, so create a temporary poly spline to find the normals. This requires extra
- * copying currently, but may be more efficient in the future if attributes have some form of CoW.
- */
-static void calculate_nurbs_normals(const NURBSpline &spline, MutableSpan<float3> normals)
-{
-  PolySpline poly_spline;
-  poly_spline.resize(spline.size());
-  poly_spline.positions().copy_from(spline.positions());
-  poly_spline.tilts().copy_from(spline.tilts());
-  normals.copy_from(poly_spline.evaluated_normals());
-}
+  const Span<float3> evaluated_normals = curves.evaluated_normals();
 
-static Array<float3> curve_normal_point_domain(const CurveEval &curve)
-{
-  Span<SplinePtr> splines = curve.splines();
-  Array<int> offsets = curve.control_point_offsets();
-  const int total_size = offsets.last();
-  Array<float3> normals(total_size);
-
-  threading::parallel_for(splines.index_range(), 128, [&](IndexRange range) {
-    for (const int i : range) {
-      const Spline &spline = *splines[i];
-      MutableSpan spline_normals{normals.as_mutable_span().slice(offsets[i], spline.size())};
-      switch (splines[i]->type()) {
-        case CURVE_TYPE_BEZIER:
-          calculate_bezier_normals(static_cast<const BezierSpline &>(spline), spline_normals);
+  Array<float3> results(curves.points_num());
+
+  threading::parallel_for(curves.curves_range(), 128, [&](IndexRange range) {
+    Vector<float3> nurbs_tangents;
+
+    for (const int i_curve : range) {
+      const IndexRange points = curves.points_for_curve(i_curve);
+      const IndexRange evaluated_points = curves.evaluated_points_for_curve(i_curve);
+
+      MutableSpan<float3> curve_normals = results.as_mutable_span().slice(points);
+
+      switch (types[i_curve]) {
+        case CURVE_TYPE_CATMULL_ROM: {
+          const Span<float3> normals = evaluated_normals.slice(evaluated_points);
+          const int resolution = resolutions[i_curve];
+          for (const int i : IndexRange(points.size())) {
+            curve_normals[i] = normals[resolution * i];
+          }
           break;
+        }
         case CURVE_TYPE_POLY:
-          calculate_poly_normals(static_cast<const PolySpline &>(spline), spline_normals);
+          curve_normals.copy_from(evaluated_normals.slice(evaluated_points));
           break;
-        case CURVE_TYPE_NURBS:
-          calculate_nurbs_normals(static_cast<const NURBSpline &>(spline), spline_normals);
+        case CURVE_TYPE_BEZIER: {
+          const Span<float3> normals = evaluated_normals.slice(evaluated_points);
+          curve_normals.first() = normals.first();
+          const Span<int> offsets = curves.bezier_evaluated_offsets_for_curve(i_curve);
+          for (const int i : IndexRange(points.size()).drop_front(1)) {
+            curve_normals[i] = normals[offsets[i - 1]];
+          }
           break;
-        case CURVE_TYPE_CATMULL_ROM:
-          BLI_assert_unreachable();
+        }
+        case CURVE_TYPE_NURBS: {
+          /* For NURBS curves there is no obvious correspondence between specific evaluated points
+           * and control points, so normals are determined by treating them as poly curves. */
+          nurbs_tangents.clear();
+          nurbs_tangents.resize(points.size());
+          const bool cyclic = curves_cyclic[i_curve];
+          const Span<float3> curve_positions = positions.slice(points);
+          bke::curves::poly::calculate_tangents(curve_positions, cyclic, nurbs_tangents);
+          switch (NormalMode(normal_modes[i_curve])) {
+            case NORMAL_MODE_Z_UP:
+              bke::curves::poly::calculate_normals_z_up(nurbs_tangents, curve_normals);
+              break;
+            case NORMAL_MODE_MINIMUM_TWIST:
+              bke::curves::poly::calculate_normals_minimum(nurbs_tangents, cyclic, curve_normals);
+              break;
+          }
           break;
+        }
       }
     }
   });
-  return normals;
+  return results;
 }
 
 VArray<float3> curve_normals_varray(const CurveComponent &component, const AttributeDomain domain)
 {
-  if (component.is_empty()) {
-    return nullptr;
+  if (!component.has_curves()) {
+    return {};
+  }
+
+  const Curves &curves_id = *component.get_for_read();
+  const bke::CurvesGeometry &curves = bke::CurvesGeometry::wrap(curves_id.geometry);
+
+  const VArray<int8_t> types = curves.curve_types();
+  if (curves.is_single_type(CURVE_TYPE_POLY)) {
+    return component.attribute_try_adapt_domain<float3>(
+        VArray<float3>::ForSpan(curves.evaluated_normals()), ATTR_DOMAIN_POINT, domain);
   }
-  const std::unique_ptr<CurveEval> curve = curves_to_curve_eval(*component.get_for_read());
+
+  Array<float3> normals = curve_normal_point_domain(curves);
 
   if (domain == ATTR_DOMAIN_POINT) {
-    Array<float3> normals = curve_normal_point_domain(*curve);
     return VArray<float3>::ForContainer(std::move(normals));
   }
 
   if (domain == ATTR_DOMAIN_CURVE) {
-    Array<float3> point_normals = curve_normal_point_domain(*curve);
-    VArray<float3> varray = VArray<float3>::ForContainer(std::move(point_normals));
     return component.attribute_try_adapt_domain<float3>(
-        std::move(varray), ATTR_DOMAIN_POINT, ATTR_DOMAIN_CURVE);
+        VArray<float3>::ForContainer(std::move(normals)), ATTR_DOMAIN_POINT, ATTR_DOMAIN_CURVE);
   }
 
   return nullptr;
@@ -456,6 +472,18 @@ static ComponentAttributeProviders create_attribute_providers_for_curve()
                                                     make_array_write_attribute<int>,
                                                     tag_component_topology_changed);
 
+  static BuiltinCustomDataLayerProvider normal_mode("normal_mode",
+                                                    ATTR_DOMAIN_CURVE,
+                                                    CD_PROP_INT8,
+                                                    CD_PROP_INT8,
+                                                    BuiltinAttributeProvider::Creatable,
+                                                    BuiltinAttributeProvider::Writable,
+                                                    BuiltinAttributeProvider::Deletable,
+                                                    curve_access,
+                                                    make_array_read_attribute<int8_t>,
+                                                    make_array_write_attribute<int8_t>,
+                                                    tag_component_normals_changed);
+
   static BuiltinCustomDataLayerProvider nurbs_knots_mode("knots_mode",
                                                          ATTR_DOMAIN_CURVE,
                                                          CD_PROP_INT8,
@@ -515,6 +543,7 @@ static ComponentAttributeProviders create_attribute_providers_for_curve()
                                       &handle_left,
                                       &handle_type_right,
                                       &handle_type_left,
+                                      &normal_mode,
                                       &nurbs_order,
                                       &nurbs_weight,
                                       &curve_type,
diff --git a/source/blender/nodes/geometry/nodes/node_geo_input_tangent.cc b/source/blender/nodes/geometry/nodes/node_geo_input_tangent.cc
index 435dd969c03..039d6b69585 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_input_tangent.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_input_tangent.cc
@@ -2,7 +2,7 @@
 
 #include "BLI_task.hh"
 
-#include "BKE_spline.hh"
+#include "BKE_curves.hh"
 
 #include "node_geometry_util.hh"
 
@@ -13,65 +13,54 @@ static void node_declare(NodeDeclarationBuilder &b)
   b.add_output<decl::Vector>(N_("Tangent")).field_source();
 }
 
-static void calculate_bezier_tangents(const BezierSpline &spline, MutableSpan<float3> tangents)
+static Array<float3> curve_tangent_point_domain(const bke::CurvesGeometry &curves)
 {
-  Span<int> offsets = spline.control_point_offsets();
-  Span<float3> evaluated_tangents = spline.evaluated_tangents();
-  for (const int i : IndexRange(spline.size())) {
-    tangents[i] = evaluated_tangents[offsets[i]];
-  }
-}
+  const VArray<int8_t> types = curves.curve_types();
+  const VArray<int> resolutions = curves.resolution();
+  const VArray<bool> cyclic = curves.cyclic();
+  const Span<float3> positions = curves.positions();
 
-static void calculate_poly_tangents(const PolySpline &spline, MutableSpan<float3> tangents)
-{
-  tangents.copy_from(spline.evaluated_tangents());
-}
+  const Span<float3> evaluated_tangents = curves.evaluated_tangents();
 
-/**
- * Because NURBS control points are not necessarily on the path, the tangent at the control points
- * is not well defined, so create a temporary poly spline to find the tangents. This requires extra
- * copying currently, but may be more efficient in the future if attributes have some form of CoW.
- */
-static void calculate_nurbs_tangents(const NURBSpline &spline, MutableSpan<float3> tangents)
-{
-  PolySpline poly_spline;
-  poly_spline.resize(spline.size());
-  poly_spline.positions().copy_from(spline.positions());
-  tangents.copy_from(poly_spline.evaluated_tangents());
-}
+  Array<float3> results(curves.points_num());
 
-static Array<float3> curve_tangent_point_domain(const CurveEval &curve)
-{
-  Span<SplinePtr> splines = curve.splines();
-  Array<int> offsets = curve.control_point_offsets();
-  const int total_size = offsets.last();
-  Array<float3> tangents(total_size);
-
-  threading::parallel_for(splines.index_range(), 128, [&](IndexRange range) {
-    for (const int i : range) {
-      const Spline &spline = *splines[i];
-      MutableSpan spline_tangents{tangents.as_mutable_span().slice(offsets[i], spline.size())};
-      switch (splines[i]->type()) {
-        case CURVE_TYPE_BEZIER: {
-          calculate_bezier_tangents(static_cast<const BezierSpline &>(spline), spline_tangents);
+  threading::parallel_for(curves.curves_range(), 128, [&](IndexRange range) {
+    for (const int i_curve : range) {
+      const IndexRange points = curves.points_for_curve(i_curve);
+      const IndexRange evaluated_points = curves.evaluated_points_for_curve(i_curve);
+
+      MutableSpan<float3> curve_tangents = results.as_mutable_span().slice(points);
+
+      switch (types[i_curve]) {
+        case CURVE_TYPE_CATMULL_ROM: {
+          Span<float3> tangents = evaluated_tangents.slice(evaluated_points);
+          const int resolution = resolutions[i_curve];
+          for (const int i : IndexRange(points.size())) {
+            curve_tangents[i] = tangents[resolution * i];
+          }
           break;
         }
-        case CURVE_TYPE_POLY: {
-          calculate_poly_tangents(static_cast<const PolySpline &>(spline), spline_tangents);
+        case CURVE_TYPE_POLY:
+          curve_tangents.copy_from(evaluated_tangents.slice(evaluated_points));
           break;
-        }
-        case CURVE_TYPE_NURBS: {
-          calculate_nurbs_tangents(static_cast<const NURBSpline &>(spline), spline_tangents);
+        case CURVE_TYPE_BEZIER: {
+          Span<float3> tangents = evaluated_tangents.slice(evaluated_points);
+          curve_tangents.first() = tangents.first();
+          const Span<int> offsets = curves.bezier_evaluated_offsets_for_curve(i_curve);
+          for (const int i : IndexRange(points.size()).drop_front(1)) {
+            curve_tangents[i] = tangents[offsets[i - 1]];
+          }
           break;
         }
-        case CURVE_TYPE_CATMULL_ROM: {
-          BLI_assert_unreachable();
+        case CURVE_TYPE_NURBS: {
+          const Span<float3> curve_positions = positions.slice(points);
+          bke::curves::poly::calculate_tangents(curve_positions, cyclic[i_curve], curve_tangents);
           break;
         }
       }
     }
   });
-  return tangents;
+  return results;
 }
 
 static VArray<float3> construct_curve_tangent_gvarray(const CurveComponent &component,
@@ -80,19 +69,25 @@ static VArray<float3> construct_curve_tangent_gvarray(const CurveComponent &comp
   if (!component.has_curves()) {
     return {};
   }
-  const std::unique_ptr<CurveEval> curve = curves_to_curve_eval(*component.get_for_read());
+
+  const Curves &curves_id = *component.get_for_read();
+  const bke::CurvesGeometry &curves = bke::CurvesGeometry::wrap(curves_id.geometry);
+
+  const VArray<int8_t> types = curves.curve_types();
+  if (curves.is_single_type(CURVE_TYPE_POLY)) {
+    return component.attribute_try_adapt_domain<float3>(
+        VArray<float3>::ForSpan(curves.evaluated_tangents()), ATTR_DOMAIN_POINT, domain);
+  }
+
+  Array<float3> tangents = curve_tangent_point_domain(curves);
 
   if (domain == ATTR_DOMAIN_POINT) {
-    Array<float3> tangents = curve_tangent_point_domain(*curve);
     return VArray<float3>::ForContainer(std::move(tangents));
   }
 
   if (domain == ATTR_DOMAIN_CURVE) {
-    Array<float3> point_tangents = curve_tangent_point_domain(*curve);
     return component.attribute_try_adapt_domain<float3>(
-        VArray<float3>::ForContainer(std::move(point_tangents)),
-        ATTR_DOMAIN_POINT,
-        ATTR_DOMAIN_CURVE);
+        VArray<float3>::ForContainer(std::move(tangents)), ATTR_DOMAIN_POINT, ATTR_DOMAIN_CURVE);
   }
 
   return nullptr;