C0 coils with splines

desc/coils.py

@@ -479,7 +479,9 @@ def to_FourierXYZ(self, N=10, grid=None, s=None, name=""):
             self.current, coords, N=N, s=s, basis="xyz", name=name
         )
 
-    def to_SplineXYZ(self, knots=None, grid=None, method="cubic", name=""):
+    def to_SplineXYZ(
+        self, knots=None, grid=None, method="cubic", name="", break_indices=None
+    ):
         """Convert coil to SplineXYZCoil.
 
         Parameters
@@ -505,6 +507,18 @@ def to_SplineXYZ(self, knots=None, grid=None, method="cubic", name=""):
             - `'catmull-rom'`: C1 cubic centripetal "tension" splines
         name : str
             name for this coil
+        break_indices : ndarray or None
+            If supplied, the spline will be a piecewise set of splines.
+            Indices of knots at which the curve breaks and is only C0 continuous (e.g.
+            continuous but with "corners" where the derivative jumps). In between each
+            set of break points, there is an unbroken spline whose start and endpoints
+            are given by `break_indices[i-1, i]`, where `i` indicates the ith spline.
+            Each (the ith) spline is interpolated independently of all other unbroken
+            splines (i+1th, i-1th, etc.) and does not consider their query points
+            (knots) when interpolating. The boundary conditions are evaluated using
+            Interpax's default where non-periodicity is assumed.
+            If None (the default), the spline will be the usual periodic spline with
+            the continuity dictated by the spline method.
 
         Returns
         -------
@@ -516,7 +530,13 @@ def to_SplineXYZ(self, knots=None, grid=None, method="cubic", name=""):
             grid = LinearGrid(zeta=knots)
         coords = self.compute("x", grid=grid, basis="xyz")["x"]
         return SplineXYZCoil.from_values(
-            self.current, coords, knots=knots, method=method, name=name, basis="xyz"
+            self.current,
+            coords,
+            knots=knots,
+            method=method,
+            name=name,
+            basis="xyz",
+            break_indices=break_indices,
         )
 
     def to_FourierRZ(self, N=10, grid=None, NFP=None, sym=False, name=""):
@@ -939,6 +959,18 @@ class SplineXYZCoil(_Coil, SplineXYZCurve):
 
     name : str
         name for this curve
+    break_indices : ndarray or None
+        If supplied, the spline will be a piecewise set of splines.
+        Indices are of knots at which the curve breaks and is only C0 continuous (e.g.
+        continuous but with "corners" where the derivative jumps). In between each set
+        of break points, there is an unbroken spline whose start and endpoints are
+        given by `break_indices[i-1, i]`, where `i` indicates the ith spline.
+        Each (the ith) spline is interpolated independently of all other unbroken
+        splines (i+1th, i-1th, etc.) and does not consider their query points
+        (knots) when interpolating. The boundary conditions are evaluated using
+        interpax's default where non-periodicity is assumed.
+        If None (the default), the spline will be the usual periodic spline with
+        the continuity dictated by the spline method.
 
     """
 
@@ -953,8 +985,9 @@ def __init__(
         knots=None,
         method="cubic",
         name="",
+        break_indices=None,
     ):
-        super().__init__(current, X, Y, Z, knots, method, name)
+        super().__init__(current, X, Y, Z, knots, method, name, break_indices)
 
     def _compute_A_or_B(
         self,
@@ -1109,7 +1142,14 @@ def compute_magnetic_vector_potential(
 
     @classmethod
     def from_values(
-        cls, current, coords, knots=None, method="cubic", name="", basis="xyz"
+        cls,
+        current,
+        coords,
+        knots=None,
+        method="cubic",
+        name="",
+        basis="xyz",
+        break_indices=None,
     ):
         """Create SplineXYZCoil from coordinate values.
 
@@ -1141,6 +1181,18 @@ def from_values(
             name for this curve
         basis : {"rpz", "xyz"}
             basis for input coordinates. Defaults to "xyz"
+        break_indices : ndarray or None
+            If supplied, the spline will be a piecewise set of splines.
+            Indices of knots at which the curve breaks and is only C0 continuous (e.g.
+            continuous but with "corners" where the derivative jumps). In between each
+            set of break points, there is an unbroken spline whose start and endpoints
+            are given by `break_indices[i-1, i]`, where `i` indicates the ith spline.
+            Each (the ith) spline is interpolated independently of all other unbroken
+            splines (i+1th, i-1th, etc.) and does not consider their query points
+            (knots) when interpolating. The boundary conditions are evaluated using
+            Interpax's default where non-periodicity is assumed.
+            If None (the default), the spline will be the usual periodic spline with
+            the continuity dictated by the spline method.
 
         Returns
         -------
@@ -1159,6 +1211,7 @@ def from_values(
             knots=curve.knots,
             method=curve.method,
             name=name,
+            break_indices=break_indices,
         )
 
 
@@ -2046,9 +2099,15 @@ def to_FourierXYZ(self, N=10, grid=None, s=None, name="", check_intersection=Tru
         )
 
     def to_SplineXYZ(
-        self, knots=None, grid=None, method="cubic", name="", check_intersection=True
+        self,
+        knots=None,
+        grid=None,
+        method="cubic",
+        name="",
+        check_intersection=True,
+        break_indices=None,
     ):
-        """Convert all coils to SplineXYZCoil representation.
+        """Convert all coils to SplineXYZCoil.
 
         Parameters
         ----------
@@ -2073,14 +2132,29 @@ def to_SplineXYZ(
             Name for the new CoilSet.
         check_intersection: bool
             Whether or not to check the coils in the new coiilset for intersections.
+        break_indices : ndarray or None
+            If supplied, the spline will be a piecewise set of splines.
+            Indices of knots at which the curve breaks and is only C0 continuous (e.g.
+            continuous but with "corners" where the derivative jumps). In between each
+            set of break points, there is an unbroken spline whose start and endpoints
+            are given by `break_indices[i-1, i]`, where `i` indicates the ith spline.
+            Each (the ith) spline is interpolated independently of all other unbroken
+            splines (i+1th, i-1th, etc.) and does not consider their query points
+            (knots) when interpolating. The boundary conditions are evaluated using
+            Interpax's default where non-periodicity is assumed.
+            If None (the default), the spline will be the usual periodic spline with
+            the continuity dictated by the spline method.
 
         Returns
         -------
         coilset : CoilSet
             New representation of the coilset parameterized by a spline for X,Y,Z.
 
         """
-        coils = [coil.to_SplineXYZ(knots, grid, method) for coil in self]
+        coils = [
+            coil.to_SplineXYZ(knots, grid, method, break_indices=break_indices)
+            for coil in self
+        ]
         return self.__class__(
             *coils,
             NFP=self.NFP,
@@ -2552,7 +2626,13 @@ def to_FourierXYZ(self, N=10, grid=None, s=None, name="", check_intersection=Tru
         return self.__class__(*coils, name=name, check_intersection=check_intersection)
 
     def to_SplineXYZ(
-        self, knots=None, grid=None, method="cubic", name="", check_intersection=True
+        self,
+        knots=None,
+        grid=None,
+        method="cubic",
+        name="",
+        check_intersection=True,
+        break_indices=None,
     ):
         """Convert all coils to SplineXYZCoil representation.
 
@@ -2579,14 +2659,29 @@ def to_SplineXYZ(
             Name for the new MixedCoilSet.
         check_intersection: bool
             Whether or not to check the coils in the new coiilset for intersections.
+        break_indices : ndarray or None
+            If supplied, the spline will be a piecewise set of splines.
+            Indices of knots at which the curve breaks and is only C0 continuous (e.g.
+            continuous but with "corners" where the derivative jumps). In between each
+            set of break points, there is an unbroken spline whose start and endpoints
+            are given by `break_indices[i-1, i]`, where `i` indicates the ith spline.
+            Each (the ith) spline is interpolated independently of all other unbroken
+            splines (i+1th, i-1th, etc.) and does not consider their query points
+            (knots) when interpolating. The boundary conditions are evaluated using
+            Interpax's default where non-periodicity is assumed.
+            If None (the default), the spline will be the usual periodic spline with
+            the continuity dictated by the spline method.
 
         Returns
         -------
         coilset : MixedCoilSet
             New representation of the coilset parameterized by a spline for X,Y,Z.
 
         """
-        coils = [coil.to_SplineXYZ(knots, grid, method) for coil in self]
+        coils = [
+            coil.to_SplineXYZ(knots, grid, method, break_indices=break_indices)
+            for coil in self
+        ]
         return self.__class__(*coils, name=name, check_intersection=check_intersection)
 
     def __add__(self, other):
@@ -2640,6 +2735,7 @@ def from_makegrid_coilfile(  # noqa: C901 - FIXME: simplify this
               the data, and will not introduce new extrema in the interpolated points
             - ``'monotonic-0'``: same as `'monotonic'` but with 0 first derivatives at
               both endpoints
+
         ignore_groups : bool
             If False, return the coils in a nested MixedCoilSet, with a sub coilset per
             single coilgroup. If there is only a single group, however, this will not