add BSpline.split() method

docs/source/math/core.rst

@@ -1147,6 +1147,8 @@ BSpline
 
     .. automethod:: measure
 
+    .. automethod:: split
+
 
 .. autoclass:: ezdxf.math.bspline.Measurement
 

notes/pages/CHANGELOG.md

@@ -7,6 +7,7 @@
 	- NEW: `BSpline.degree_elevation()` method
 	- NEW: `BSpline.point_inversion()` method
 	- NEW: `BSpline.measure()` method
+	- NEW: `BSpline.split()` method
 	- NEW: `BSpline.insert_knot()` and `BSpline.knot_refinement()` supports rational splines
 	- BUGFIX: Exported `MESH` entities  without vertices or faces create invalid DXF files
 		- {{issue 1219}}

src/ezdxf/math/bspline.py

@@ -41,7 +41,6 @@
     estimate_end_tangent_magnitude,
     distance_point_line_3d,
     arc_angle_span_deg,
-    ABS_TOL,
 )
 from .bbox import BoundingBox
 from ezdxf.math import linalg
@@ -1396,6 +1395,18 @@ def measure(self, segments: int = 100) -> Measurement:
         """
         return Measurement(self, segments)
 
+    def split(self, t: float) -> tuple[BSpline, BSpline]:
+        """Splits the B-spline at parameter `t` and returns two new B-splines.
+
+        Raises:
+            ValuerError: t out of range 0 < t < max_t
+
+        .. versionadded:: 1.4
+
+        """
+
+        return split_bspline(self, t)
+
 
 def subdivide_params(p: list[float]) -> Iterable[float]:
     for i in range(len(p) - 1):
@@ -2025,10 +2036,18 @@ def _measure_spline(self, segments: int) -> None:
 
 
 def split_bspline(spline: BSpline, t: float) -> tuple[BSpline, BSpline]:
-    """Splits a B-spline at a specified parameter value."""
-    if t < ABS_TOL:
+    """Splits a B-spline at a parameter t.
+
+    Raises:
+        ValuerError: t out of range 0 < t < max_t
+
+    .. versionadded:: 1.4
+
+    """
+    tol = 1e-12
+    if t < tol:
         raise ValueError("t must be greater than 0")
-    if t > spline.max_t - ABS_TOL:
+    if t > spline.max_t - tol:
         raise ValueError("t must be smaller than max_t")
     order = spline.order
 

tests/test_06_math/test_628_bspline_tools.py

@@ -219,5 +219,14 @@ def test_extents(self, spline):
         assert mtool.extmax.isclose((5, 1.19263675))
 
 
+def test_split_spline():
+    spline = BSpline(CONTROL_POINTS)
+    _, mid_t, _ = spline.measure().divide(2)
+    sp1, sp2 = spline.split(mid_t)
+    l1 = sp1.measure().length
+    l2 = sp2.measure().length
+    assert abs(l1 - l2) < 0.01
+
+
 if __name__ == "__main__":
     pytest.main([__file__])