fixed problem with type conversions in Line3D

manim/mobject/three_d/three_dimensions.py

@@ -926,6 +926,10 @@ def __init__(
     ):
         self.thickness = thickness
         self.resolution = (2, resolution) if isinstance(resolution, int) else resolution
+
+        start = np.array(start,np.float64)
+        end = np.array(end,np.float64)
+
         self.set_start_and_end_attrs(start, end, **kwargs)
         if color is not None:
             self.set_color(color)

tests/test_graphical_units/test_threed.py

@@ -172,3 +172,10 @@ def test_get_start_and_end_Arrow3d():
     assert np.allclose(
         arrow.get_end(), end, atol=0.01
     ), "end points of Arrow3D do not match"
+
+def test_type_conversion_in_Line3D():
+    start,end = [0,0,0],[1,1,1]
+    line = Line3D(start,end)
+    type_table = [type(item) for item in [*line.get_start(),*line.get_end()]]
+    bool_table = [t == np.float64 for t in type_table]
+    assert all(bool_table), "Types of start and end points are not np.float64"