Add cubic hermite spline to geom

libs/geom/include/psemek/geom/hermite.hpp

@@ -0,0 +1,26 @@
+#pragma once
+
+namespace psemek::geom
+{
+
+	template <typename T>
+	struct cubic_hermite
+	{
+		T a[3];
+
+		cubic_hermite() = default;
+		cubic_hermite(T p0, T m0, T p1, T m1)
+		{
+			a[0] = p0;
+			a[1] = m0;
+			a[2] = - 3 * p0 - 2 * m0 + 3 * p1 - m1;
+			a[3] = 2 * p0 + m0 - 2 * p1 + m1;
+		}
+
+		T operator() (T t) const
+		{
+			return a[0] + t * (a[1] + t * (a[2] + t * a[3]));
+		}
+	};
+
+}