1 files changed, 54 insertions, 0 deletions
diff --git a/source/blender/geometry/GEO_add_curves_on_mesh.hh b/source/blender/geometry/GEO_add_curves_on_mesh.hh
new file mode 100644
index 00000000000..cf60a8e8ace
--- /dev/null
+++ b/source/blender/geometry/GEO_add_curves_on_mesh.hh
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+#include "BLI_float4x4.hh"
+#include "BLI_kdtree.h"
+#include "BLI_math_vector.hh"
+#include "BLI_span.hh"
+
+#include "BKE_bvhutils.h"
+#include "BKE_curves.hh"
+
+#include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+
+namespace blender::geometry {
+
+struct AddCurvesOnMeshInputs {
+  /** Information about the root points where new curves should be generated. */
+  Span<float3> root_positions_cu;
+  Span<float3> bary_coords;
+  Span<int> looptri_indices;
+
+  /** Determines shape of new curves. */
+  bool interpolate_length = false;
+  bool interpolate_shape = false;
+  bool interpolate_point_count = false;
+  float fallback_curve_length = 0.0f;
+  int fallback_point_count = 0;
+
+  /** Information about the surface that the new curves are attached to. */
+  const Mesh *surface = nullptr;
+  BVHTreeFromMesh *surface_bvh = nullptr;
+  Span<MLoopTri> surface_looptris;
+  Span<float2> surface_uv_map;
+  Span<float3> corner_normals_su;
+
+  /** Transformation matrices. */
+  float4x4 curves_to_surface_mat;
+  float4x4 surface_to_curves_normal_mat;
+
+  /**
+   * KD-Tree that contains the root points of existing curves. This is only necessary when
+   * interpolation is used.
+   */
+  KDTree_3d *old_roots_kdtree = nullptr;
+};
+
+/**
+ * Generate new curves on a mesh surface with the given inputs. Existing curves stay intact.
+ */
+void add_curves_on_mesh(bke::CurvesGeometry &curves, const AddCurvesOnMeshInputs &inputs);
+
+}  // namespace blender::geometry