added particle visualization methods

particle.py

@@ -76,7 +76,7 @@ class Particles:
         attr = {}
         for key in self.attr:
             attr[key] = self.attr[key].copy()
-        return Particles(self.num,self.time,attr,period)
+        return Particles(self.num,self.time,attr,self.period)
     def add_attribute(self,key,val):
         import numpy
         if isinstance(val,(tuple,list,numpy.ndarray)):
@@ -125,6 +125,22 @@ class Particles:
                 key = ('x','y','z')[axis]
                 self.attr[key] %= self.period[axis]
         return
+    def to_vtk(self,deep=False):
+        import pyvista as pv
+        import numpy as np
+        position = np.vstack([self.attr[key] for key in ('x','y','z')]).transpose()
+        mesh = pv.PolyData(position,deep=deep)
+        for key in self.attr:
+            mesh[key] = self.attr[key]
+        return mesh
+
+    def glyph(self,theta_resolution=10,phi_resolution=10,deep=False):
+        import pyvista as pv
+        assert self.has_attribute('r'), "Attribute 'r' required."
+        geom = pv.Sphere(radius=1,theta_resolution=theta_resolution,
+                    phi_resolution=phi_resolution)
+        return self.to_vtk(deep=deep).glyph(scale='r',factor=1,geom=geom)
+
 class Trajectories:
     def __init__(self,part,unraveled=False,copy_particles=False):
         import numpy