Add get_tangent() to curves

src/classy_blocks/construct/curves/curve.py

@@ -7,9 +7,9 @@
 
 from classy_blocks.base.element import ElementBase
 from classy_blocks.construct.point import Point
-from classy_blocks.types import NPPointListType, NPPointType, ParamCurveFuncType, PointListType, PointType
+from classy_blocks.types import NPPointListType, NPPointType, ParamCurveFuncType, PointListType, PointType, VectorType
 from classy_blocks.util import functions as f
-from classy_blocks.util.constants import DTYPE
+from classy_blocks.util.constants import DTYPE, TOL
 
 
 class CurveBase(ElementBase):
@@ -79,6 +79,13 @@ def get_closest_param(self, point: PointType) -> float:
         i_distance = np.argmin(distances)
         return params[i_distance]
 
+    def get_tangent(self, param: float, delta: float = TOL) -> VectorType:
+        """Returns a normalized tangent to the curve at given parameter"""
+        prev_point = self.get_point(param - delta / 2)
+        next_point = self.get_point(param + delta / 2)
+
+        return f.unit_vector(next_point - prev_point)
+
 
 class PointCurveBase(CurveBase):
     """A base object for curves, defined by a list of points"""

tests/test_construct/test_curves/test_analytic.py

@@ -55,6 +55,16 @@ def test_transform(self):
         with self.assertRaises(NotImplementedError):
             self.curve.translate([1, 1, 1])
 
+    @parameterized.expand(
+        (
+            (0, [0, 1, 0]),
+            (np.pi / 2, [-1, 0, 0]),
+            (np.pi, [0, -1, 0]),
+        )
+    )
+    def test_tangent(self, param, tangent):
+        np.testing.assert_almost_equal(self.curve.get_tangent(param), tangent)
+
 
 class LineCurveTests(unittest.TestCase):
     def setUp(self):