TranslationalActions.py

import math
import vtk
from PythonMetricsCalculator import PerkEvaluatorMetric

class TranslationalActions( PerkEvaluatorMetric ):

  # Note: An action is defined as a time period where the absolute velocity of motion is greater than some threshold
  VELOCITY_THRESHOLD = 50 #mm/s
  TIME_THRESHOLD = 0.2 #s

  # Static methods
  @staticmethod
  def GetMetricName():
    return "Translational Actions"
  
  @staticmethod  
  def GetMetricUnit():
    return "count"
    
    
  # Instance methods  
  def __init__( self ):
    PerkEvaluatorMetric.__init__( self )
    
    self.numActions = 0
    self.actionState = 0
    self.completeActionTime = 0
    
    self.timePrev = None
    self.matrixPrev = None
    
  def AddTimestamp( self, time, matrix, point, role ):  
    if ( time == self.timePrev ):
      return
    
    if ( self.timePrev == None or self.matrixPrev == None ):
      self.timePrev = time
      self.matrixPrev = vtk.vtkMatrix4x4()
      self.matrixPrev.DeepCopy( matrix )
      return
    
    invertPrev = vtk.vtkMatrix4x4()
    invertPrev.DeepCopy( self.matrixPrev )
    invertPrev.Invert()
    
    currChangeMatrix = vtk.vtkMatrix4x4()
    vtk.vtkMatrix4x4().Multiply4x4( matrix, invertPrev, currChangeMatrix )

    currChangeTransform = vtk.vtkTransform()
    currChangeTransform.SetMatrix( currChangeMatrix )
    
    currVelocity = [ 0, 0, 0 ]
    currChangeTransform.GetPosition( currVelocity )
    
    vtk.vtkMath().MultiplyScalar( currVelocity, 1 / ( time - self.timePrev ) )
    currAbsVelocity = math.sqrt( currVelocity[ 0 ] * currVelocity[ 0 ] + currVelocity[ 1 ] * currVelocity[ 1 ] + currVelocity[ 2 ] * currVelocity[ 2 ] )
    
    currentTestState = ( currAbsVelocity > TranslationalActions.VELOCITY_THRESHOLD )
    
    if ( currentTestState == self.actionState ):
      self.completeActionTime = time
    else:
      if ( ( time - self.completeActionTime ) > TranslationalActions.TIME_THRESHOLD ):
        self.actionState = currentTestState
        self.completeActionTime = time
        if ( currentTestState == 1 ):
          self.numActions += 1
        
    self.timePrev = time
    self.matrixPrev = vtk.vtkMatrix4x4()
    self.matrixPrev.DeepCopy( matrix )

  def GetMetric( self ):
    return self.numActions