added splines

examples/00-load/create-spline.py

@@ -0,0 +1,48 @@
+"""
+.. _ref_create_spline:
+
+Creating a Spline
+~~~~~~~~~~~~~~~~~
+
+Create a spline from numpy arrays
+"""
+
+# sphinx_gallery_thumbnail_number = 2
+import pyvista as pv
+import numpy as np
+
+
+################################################################################
+# Create a dataset to plot
+
+# data
+n_points = 100
+theta = np.linspace(-4 * np.pi, 4 * np.pi, n_points)
+z = np.linspace(-2, 2, n_points)
+r = z**2 + 1
+x = r * np.sin(theta)
+y = r * np.cos(theta)
+points = np.column_stack((x, y, z))
+
+################################################################################
+# Now pass the NumPy data to PyVista
+
+# Create spline with 1000 interpolation points
+spline = pv.Spline(points, 1000)
+
+################################################################################
+# Plot spline as a tube
+
+# add scalars to spline and plot it
+spline['scalars'] = np.arange(spline.n_points)
+tube = spline.tube(radius=0.1)
+tube.plot(smooth_shading=True)
+
+################################################################################
+# Line can also be plotted as a plain line
+
+# generate same spline with 400 interpolation points
+spline = pv.Spline(points, 400)
+
+# plot without scalars
+spline.plot(line_width=4, color='k')

pyvista/geometric_objects.py

@@ -619,6 +619,48 @@ def parametric_keywords(parametric_function, min_u=0, max_u=2*pi,
     parametric_function.SetClockwiseOrdering(clockwise)
 
 
+def Spline(points, n_points=None):
+    """Create a spline from points
+
+    Parameters
+    ----------
+    points : np.ndarray
+        Array of points to build a spline out of.  Array must be 3D
+        and directionally ordered.
+
+    n_points : int, optional
+        Number of points to interpolate along the points array.
+
+    Returns
+    -------
+    spline : pyvista.PolyData
+        Line mesh of spline.
+
+    Examples
+    --------
+    Construct a spline
+    >>> import numpy as np
+    >>> import pyvista as pv
+    >>> theta = np.linspace(-4 * np.pi, 4 * np.pi, 100)
+    >>> z = np.linspace(-2, 2, 100)
+    >>> r = z**2 + 1
+    >>> x = r * np.sin(theta)
+    >>> y = r * np.cos(theta)
+    >>> points = np.column_stack((x, y, z))
+    >>> spline = pv.Spline(points, 1000)
+    """
+    spline_function = vtk.vtkParametricSpline()
+    spline_function.SetPoints(pyvista.vtk_points(points, False))
+
+    # get interpolation density
+    u_res = n_points
+    if u_res is None:
+        u_res = points.shape[0]
+
+    u_res -= 1
+    return surface_from_para(spline_function, u_res)
+
+
 def surface_from_para(parametric_function, u_res=100, v_res=100,
                       w_res=100, **kwargs):
     """Construct a mesh from a parametric function.

pyvista/utilities.py

@@ -333,6 +333,7 @@ def wrap(vtkdataset):
         'vtkImageData' : pyvista.UniformGrid,
         'vtkStructuredPoints' : pyvista.UniformGrid,
         'vtkMultiBlockDataSet' : pyvista.MultiBlock,
+        # 'vtkParametricSpline' : pyvista.Spline,
         }
     # Otherwise, we assume a VTK data object was passed
     if hasattr(vtkdataset, 'GetClassName'):

tests/test_geometric_objects.py

@@ -76,3 +76,15 @@ def test_supertoroid():
 def test_ellipsoid():
     geom = pyvista.Ellipsoid()
     assert np.any(geom.points)
+
+
+def test_spline():
+    theta = np.linspace(-4 * np.pi, 4 * np.pi, 100)
+    z = np.linspace(-2, 2, 100)
+    r = z**2 + 1
+    x = r * np.sin(theta)
+    y = r * np.cos(theta)
+
+    points = np.column_stack((x, y, z))
+    spline = pyvista.Spline(points, 1000)
+    assert spline.n_points == 1000