Cory,
No, I’m using numpy.arctan2 – sorry, always think of it as atan2.
What I’m doing now is:
# Undeformed Sector Angles (degrees about Y-axis, 0=FP)
numPts=block.GetNumberOfPoints()
node_angles=zeros( (numPts,1) )
x_undef,y_undef,z_undef=calc_node_undeformed_coords(block)
node_angles=arctan2(x_undef,z_undef)*180.0/pi
return node_angles
So, I’m not looping, as you suggest. I am later doing a custom
point-data-to-cell-data by looping over millions of cells and finding each
cells nodes and averaging them, but I’ve failed to get
vtk.vtkPointDataToCellData to work inside my Programmable filter, so I don’t
have a good alternative.
I keep meaning to take out the cell angles and see how much that speeds it up,
but haven’t done that yet.
Thanks for looking at this.
Dennis
From: Cory Quammen [mailto:[email protected]]
Sent: Monday, April 30, 2018 1:44 PM
To: kenichiro yoshimi <[email protected]>
Cc: Dennis Conklin <[email protected]>; Paraview
([email protected]) <[email protected]>
Subject: Re: [Paraview] [EXT] RE: [EXTERNAL] Calculating cylindrical coordinates
Dennis,
First, do you mean numpy.arctan2? I don't see that numpy.atan2 exists,but
math.atan2 exists.
Second, I suspect you are looping over millions of points in Python and are
calling numpy.arctan2 on single X, Y values. Looping in Python like that will
be very slow. Instead, you can get all your X values into one numpy array and
do the same with your Y values, then make a single call to numpy.atan2. Here's
an example:
>>> from paraview.simple import *
>>> import numpy
>>> x = [1, 2, 3, 4]
>>> y = [5, 6, 7, 8]
>>> numpy.arctan2(y, x)
array([ 1.37340077, 1.24904577, 1.16590454, 1.10714872])
To get the X and Y arrays, you can use the numpy adapter:
>>> from vtk.numpy_interface import dataset_adapter as dsa
>>> wrappedData = dsa.WrapDataObject(polydata)
>>> X = wrappedData.Points[:,0]
>>> Y = wrappedData.Points[:,1]
>>> result = numpy.arctan2(Y, X)
Hope that helps,
Cory
On Sat, Apr 28, 2018 at 1:25 AM, kenichiro yoshimi
<[email protected]<mailto:[email protected]>> wrote:
Hi Dennis,
You can calculate cylindrical coordinates by utilizing vtkCylindricalTransform
within the python programmable filter. It is something like below and faster
than numpy.
---
import vtk
input = self.GetInput()
output = self.GetOutput()
transform = vtk.vtkCylindricalTransform()
transformFilter = vtk.vtkTransformFilter()
transformFilter.SetInputData(input)
transformFilter.SetTransform(transform.GetInverse())
transformFilter.Update()
output.ShallowCopy(transformFilter.GetOutput())
---
This converts (x,y,z) coordinates to (r,theta,z) coordinates by GetInverse
method,
where the angles are calculated by the following equation to change range to
[0, 2*pi]:
theta = pi + atan2(-y, -x).
Regards
2018-04-28 5:25 GMT+09:00 Dennis Conklin
<[email protected]<mailto:[email protected]>>:
Alan,
Yes, I am calling it many times at the same angular location, but it’s tough to
know you’re at the same angular location without calculating the angle.
Also, C++ is definitely orders of magnitude quicker, but once I have to compile
routines into Paravew life gets very complicated. We barely survived
compiling for cluster use and I haven’t written C++ for at least 20 years.
So, if possible, I would like a clever external add-on that wouldn’t require us
to re-compile PV everytime we update our version. I have visions of library
errors in my nightmares!
Dennis
From: Scott, W Alan [mailto:[email protected]<mailto:[email protected]>]
Sent: Friday, April 27, 2018 4:00 PM
To: Dennis Conklin
<[email protected]<mailto:[email protected]>>; Paraview
([email protected]<mailto:[email protected]>)
<[email protected]<mailto:[email protected]>>
Subject: [EXT] RE: [EXTERNAL] [Paraview] Calculating cylindrical coordinates
CAUTION: EXTERNAL email. Please think before clicking on any links or
attachments.
Are there places on the cylinder you are calling atan2 with the same inputs,
returning the same data, lots of times? Alternatively, could you calculate
this in the simulation, and just add it to the simulation output? I am
speculating that a C++ call to atan2 may be faster than numpy?
Alan
From: ParaView [mailto:[email protected]] On Behalf Of Dennis
Conklin
Sent: Friday, April 27, 2018 1:39 PM
To: Paraview ([email protected]<mailto:[email protected]>)
<[email protected]<mailto:[email protected]>>
Subject: [EXTERNAL] [Paraview] Calculating cylindrical coordinates
All,
If I wanted to run atan2(X,Y) on millions and millions of nodes to calculate
cylindrical coordinates, but found that numpy.atan2 in a Programmable Filter
was taking 45 minutes to run, what should I do to make it much faster?
Thanks for any hints
Dennis
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Kitware, Inc.
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