1 files changed, 138 insertions, 0 deletions
diff --git a/source/blender/blenkernel/intern/curve_bezier.cc b/source/blender/blenkernel/intern/curve_bezier.cc
new file mode 100644
index 00000000000..84009ad51c0
--- /dev/null
+++ b/source/blender/blenkernel/intern/curve_bezier.cc
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include "BKE_attribute_math.hh"
+#include "BKE_curves.hh"
+
+namespace blender::bke::curves::bezier {
+
+bool segment_is_vector(const Span<int8_t> handle_types_left,
+                       const Span<int8_t> handle_types_right,
+                       const int segment_index)
+{
+  BLI_assert(handle_types_left.index_range().drop_back(1).contains(segment_index));
+  return handle_types_right[segment_index] == BEZIER_HANDLE_VECTOR &&
+         handle_types_left[segment_index + 1] == BEZIER_HANDLE_VECTOR;
+}
+
+bool last_cylic_segment_is_vector(const Span<int8_t> handle_types_left,
+                                  const Span<int8_t> handle_types_right)
+{
+  return handle_types_right.last() == BEZIER_HANDLE_VECTOR &&
+         handle_types_left.first() == BEZIER_HANDLE_VECTOR;
+}
+
+void calculate_evaluated_offsets(const Span<int8_t> handle_types_left,
+                                 const Span<int8_t> handle_types_right,
+                                 const bool cyclic,
+                                 const int resolution,
+                                 MutableSpan<int> evaluated_offsets)
+{
+  const int size = handle_types_left.size();
+  BLI_assert(evaluated_offsets.size() == size);
+
+  if (size == 1) {
+    evaluated_offsets.first() = 1;
+    return;
+  }
+
+  int offset = 0;
+
+  for (const int i : IndexRange(size - 1)) {
+    offset += segment_is_vector(handle_types_left, handle_types_right, i) ? 1 : resolution;
+    evaluated_offsets[i] = offset;
+  }
+
+  if (cyclic) {
+    offset += last_cylic_segment_is_vector(handle_types_left, handle_types_right) ? 1 : resolution;
+    evaluated_offsets.last(1) = offset;
+  }
+  else {
+    offset++;
+  }
+
+  evaluated_offsets.last() = offset;
+}
+
+void evaluate_segment(const float3 &point_0,
+                      const float3 &point_1,
+                      const float3 &point_2,
+                      const float3 &point_3,
+                      MutableSpan<float3> result)
+{
+  BLI_assert(result.size() > 0);
+  const float inv_len = 1.0f / static_cast<float>(result.size());
+  const float inv_len_squared = inv_len * inv_len;
+  const float inv_len_cubed = inv_len_squared * inv_len;
+
+  const float3 rt1 = 3.0f * (point_1 - point_0) * inv_len;
+  const float3 rt2 = 3.0f * (point_0 - 2.0f * point_1 + point_2) * inv_len_squared;
+  const float3 rt3 = (point_3 - point_0 + 3.0f * (point_1 - point_2)) * inv_len_cubed;
+
+  float3 q0 = point_0;
+  float3 q1 = rt1 + rt2 + rt3;
+  float3 q2 = 2.0f * rt2 + 6.0f * rt3;
+  float3 q3 = 6.0f * rt3;
+  for (const int i : result.index_range()) {
+    result[i] = q0;
+    q0 += q1;
+    q1 += q2;
+    q2 += q3;
+  }
+}
+
+void calculate_evaluated_positions(const Span<float3> positions,
+                                   const Span<float3> handles_left,
+                                   const Span<float3> handles_right,
+                                   const Span<int> evaluated_offsets,
+                                   MutableSpan<float3> evaluated_positions)
+{
+  BLI_assert(evaluated_offsets.last() == evaluated_positions.size());
+  BLI_assert(evaluated_offsets.size() == positions.size());
+
+  /* Evaluate the first segment. */
+  evaluate_segment(positions.first(),
+                   handles_right.first(),
+                   handles_left[1],
+                   positions[1],
+                   evaluated_positions.take_front(evaluated_offsets.first()));
+
+  /* Give each task fewer segments as the resolution gets larger. */
+  const int grain_size = std::max(evaluated_positions.size() / positions.size() * 32, 1L);
+  threading::parallel_for(
+      positions.index_range().drop_back(1).drop_front(1), grain_size, [&](IndexRange range) {
+        for (const int i : range) {
+          const IndexRange evaluated_range = offsets_to_range(evaluated_offsets, i - 1);
+          if (evaluated_range.size() == 1) {
+            evaluated_positions[evaluated_range.first()] = positions[i];
+          }
+          else {
+            evaluate_segment(positions[i],
+                             handles_right[i],
+                             handles_left[i + 1],
+                             positions[i + 1],
+                             evaluated_positions.slice(evaluated_range));
+          }
+        }
+      });
+
+  /* Evaluate the final cyclic segment if necessary. */
+  const IndexRange evaluated_range = offsets_to_range(evaluated_offsets, positions.size() - 2);
+  if (evaluated_range.size() == 1) {
+    evaluated_positions.last() = positions.last();
+  }
+  else {
+    evaluate_segment(positions.last(),
+                     handles_right.last(),
+                     handles_left.first(),
+                     positions.first(),
+                     evaluated_positions.slice(evaluated_range));
+  }
+}
+
+/** \} */
+
+}  // namespace blender::bke::curves::bezier