[SOLVED] Track a target point/node on a volumetric mesh

Hey Siming,

To my knowledge, there is no direct way. However, using python it can be pretty easy!
All you need to do is to add this in your XML scene:

<Node name="root" />
	<RequiredPlugin name="SofaPython" pluginName="SofaPython" />
	<PythonScriptController filename="trackingScript.py" classname="trackingScript"/>

	...
</Node>

and create your tracking script using python:

import Sofa
import sys

#your python class
class trackingScript(Sofa.PythonScriptController):
	
	# after creation of the graph, then initialization comes
	# you need to retrieve the MechanicalObject associated to your object
	
	def initGraph(self,rootnode):
    	self.yourNode = rootnode.getChild("YourNode")
    	self.yourMO = self.yourNode.getObject("name_of_your_MechanicalObject")
    	return 0

	# called on each animation step
    def onBeginAnimationStep(self,dt):
        
        # here access the node you want ..
        vector_of_position = self.yourMO.findData('position').value
        print vector_of_position[10][0]
        return 0

Hope this helps,

Hugo

Hi Siming,

If I understand you correctly, I recently did something very similar to what you are trying to accomplish. I export the SOFA result using the VTKExporter and then wrote a “voxelize” program which uses VTK to resample the results into a regular grid.
The “vtkProbeFilter” does what you want. Here’s a small excerpt from the code:

    // Perform the interpolation
    vtkSmartPointer<vtkProbeFilter> probeFilter = vtkSmartPointer<vtkProbeFilter>::New();
    probeFilter->SetValidPointMaskArrayName("mesh");
    probeFilter->SetSourceData( ugrid );
    probeFilter->SetInputData( cellCenters );      // Interpolate 'Source' at these points
    probeFilter->Update();

Here, “ugrid” is a vtkUnstructuredGrid, “cellCenters” is a vtkPolyData which was previously filled with points (which can either be done manually or, if you already have the goal structure, by taking the cell centers of the image which you mentioned).

Cheers,
Micha