Attach arrow to mesh

ParaView Support
#1

Hi all,

I have a mesh data set that I can deform using Warp by Vector filter. I also have another data set containing a single force vector (at location [0,0,0], with components [fx(t),fy(t),fz(t)]. I can use Transform filter to move that vector about, but I really want to attach it to a point of the mesh (or something to that effect). Any suggestions?

Kind regards, Eelco

#2

Not very clear. Maybe you are looking for RessampleWithDataset filter ? Or Glyph ?

#3

Sorry for the belated response.

I added some files in an attempt to clarify my question. The mesh consist of just a few random elements due to confidentiality, but i’ll do for now.

“eturret” is a dataset containing the mesh and has attributes displacement and deformation. Only Deformation has values, the displacement is all zero for now.

“mooring” is a dataset containing the data of a force vector.

I use Glyph to create an arrow for the mooring dataset. But I want to move (attach) the base of that arrow to a point on the mesh. Any point really. And I want it to follow that point, even if I apply the Warp by Vector filter to the mesh.

Hopefully this clarifies a little!

eturret.h5 (129.9 KB) eturret.xmf (45.1 KB) mooring.h5 (41.2 KB) mooring.xmf (35.3 KB) test.pvsm (564.2 KB)

#4

There is not direct way to do that.

But there is the “specific” way and the “convoluted” way.

For the specific way, you will need to implement a simple programmable filter that will take two inputs, the mesh and the mooring, and copy the mooring vector into each points of the mesh. You can then use a glyph without any issue. You still need to implement it in python. Let me know if you need help.
https://www.paraview.org/Wiki/Python_Programmable_Filter

The convoluted way is a bit more tricky but does not require any python. Here it is :
testConvoluted.pvsm (834.6 KB)

The idea of this is that we consider your Arrow Glyph as a source input for a Glyph with custom source applied on the mesh. The problem is that your mooring is not located in the origin on the space, so I had to translate it. If the translation is constant with all your moorings or if this translation can be removed in post-process, this solution might be acceptable.

#5

I managed to get it working using the programmable filter. The script will attach the vector to the nearest node wrt to the coordinates you put in manually. Here’s how I went about it:

  1. Put the mesh, the warped mesh and the mooring (vector) in a GroupDataSet
  2. Push the GroupDataSet through a programmable filter with the code below.
import numpy as np

# Input coordinates. The script will find the nearest node in the mesh.
x,y,z = 0,0,-1e3

input = self.GetInputDataObject(0, 0)

iter = input.NewIterator()
iter.UnRegister(None)
iter.InitTraversal()

# Warped mesh data set
curInput1 = iter.GetCurrentDataObject()
iter.GoToNextItem()
# Vector data set
curInput2 = iter.GetCurrentDataObject()
iter.GoToNextItem()
# Mesh data set
curInput3 = iter.GetCurrentDataObject()


# initialize currOutput
curOutput = curInput2.NewInstance()
curOutput.UnRegister(None)
curOutput.ShallowCopy(curInput2)

# create output and attach curOutput
output = self.GetOutputDataObject(0)
output.CopyStructure(input)
output.SetDataSet(iter, curOutput)

loc = []
NrOfPt = curInput3.GetNumberOfPoints()
for i in range(0,NrOfPt):
    loc.append(curInput3.GetPoint(i))
    
loc = np.asarray(loc)
loc[:,0]-=x
loc[:,1]-=y
loc[:,2]-=z

lsq     = lambda x: x[:,0]**2+x[:,1]**2+x[:,2]**2
NodeNr  = np.argmin(lsq(loc))

# Set currOutput to the node
loc = curInput1.GetPoint(NodeNr)
newPoints = vtk.vtkPoints()
newPoints.InsertPoint(0,loc[0],loc[1],loc[2])
curOutput.SetPoints(newPoints)
  1. Create an arrow glyph.

DRAWBACK:
Slow. Every time step the nearest node is calculated (which is always the same). It would be better to do this calculation independent of time, but I don’t know how to do that yet. Any advice is welcome!

KR, Eelco

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