ENH: new seam strategy from prusa2.5

As title. Thanks @Prusa

Signed-off-by: salt.wei <salt.wei@bambulab.com>
Change-Id: I2fa177e27ac53211952ea9b6c62e98182b8f05ce

src/libslic3r/NormalUtils.hpp

@@ -0,0 +1,69 @@
+#ifndef slic3r_NormalUtils_hpp_
+#define slic3r_NormalUtils_hpp_
+
+#include "Point.hpp"
+#include "Model.hpp"
+
+namespace Slic3r {
+
+/// <summary>
+/// Collection of static function
+/// to create normals
+/// </summary>
+class NormalUtils
+{
+public:
+    using Normal = Vec3f;
+    using Normals = std::vector<Normal>;
+    NormalUtils() = delete; // only static functions
+
+    enum class VertexNormalType {
+        AverageNeighbor,
+        AngleWeighted,
+        NelsonMaxWeighted
+    };
+
+    /// <summary>
+    /// Create normal for triangle defined by indices from vertices
+    /// </summary>
+    /// <param name="indices">index into vertices</param>
+    /// <param name="vertices">vector of vertices</param>
+    /// <returns>normal to triangle(normalized to size 1)</returns>
+    static Normal create_triangle_normal(
+        const stl_triangle_vertex_indices &indices,
+        const std::vector<stl_vertex> &    vertices);
+
+    /// <summary>
+    /// Create normals for each vertices
+    /// </summary>
+    /// <param name="its">indices and vertices</param>
+    /// <returns>Vector of normals</returns>
+    static Normals create_triangle_normals(const indexed_triangle_set &its);
+
+    /// <summary>
+    /// Create normals for each vertex by averaging neighbor triangles normal
+    /// </summary>
+    /// <param name="its">Triangle indices and vertices</param>
+    /// <param name="type">Type of calculation normals</param>
+    /// <returns>Normal for each vertex</returns>
+    static Normals create_normals(
+        const indexed_triangle_set &its,
+        VertexNormalType type = VertexNormalType::NelsonMaxWeighted);
+    static Normals create_normals_average_neighbor(const indexed_triangle_set &its);
+    static Normals create_normals_angle_weighted(const indexed_triangle_set &its);
+    static Normals create_normals_nelson_weighted(const indexed_triangle_set &its);
+
+    /// <summary>
+    /// Calculate angle of trinagle side.
+    /// </summary>
+    /// <param name="i">index to indices, define angle point</param>
+    /// <param name="indice">address to vertices</param>
+    /// <param name="vertices">vertices data</param>
+    /// <returns>Angle [in radian]</returns>
+    static float indice_angle(int                            i,
+                              const Vec3crd &                indice,
+                              const std::vector<stl_vertex> &vertices);
+};
+
+} // namespace Slic3r
+#endif // slic3r_NormalUtils_hpp_