<!-- GENERATED by tools/generators/examplesDocsEmitter.py from python/ - do not edit -->
(examples-mouseinteractionexample)=
# mouseInteractionExample.py

You can view and download this file on Github: [mouseInteractionExample.py](https://github.com/jgerstmayr/EXUDYN/tree/master/python/Examples/mouseInteractionExample.py)

```{code-block} python
:linenos:

#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details: This is the first interactive mouse motion example; 
#          use your mouse to drag the end of the chain;
#          models a chain of 3D rigid bodies connected with revolute joints;
#          may require RESTART of python kernel to work properly!
#
# Author:   Johannes Gerstmayr
# Date:     2020-12-06
#
# Copyright:This file is part of Exudyn. Exudyn is free software. You can redistribute it and/or modify it under the terms of the Exudyn license. See 'LICENSE.txt' for more details.
#
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

import exudyn as exu
from exudyn.itemInterface import *
import numpy as np
from exudyn.utilities import * #includes itemInterface and rigidBodyUtilities
import exudyn.graphics as graphics

from math import sin, cos, pi

SC = exu.SystemContainer()
mbs = SC.AddSystem()

activateWithKeyPress = True #activate mouse drag with keypress 'D'

color = [0.1,0.1,0.8,1]

sx = 0.25
sy = 0.1
sz = 0.1

nBodies = 16

Ltot = nBodies*sx
sc = 4 #size of coordinate system
coordSys0 = graphics.Cylinder([0,0,0], [sz,0,0], 0.01, color=graphics.color.red)
coordSys1 = graphics.Cylinder([0,0,0], [0,sz,0], 0.01, color=graphics.color.green)
coordSys2 = graphics.Cylinder([0,0,0], [0,0,sz], 0.01, color=graphics.color.blue)
oGround=mbs.AddObject(ObjectGround(referencePosition= [0,0,0], 
                                   visualization=VObjectGround(graphicsData= [coordSys0, coordSys1, coordSys2])))

m=1 #mass
density = 2000

nodeList=[]
objectList=[]

nRB=-1
com=[0,0,0]
 
RBinertia = InertiaCuboid(density=density, sideLengths=[sx,sy,sz])

mPosGround = mbs.AddMarker(MarkerBodyRigid(bodyNumber = oGround, 
                                            localPosition=[0,0,0]))
mPosLast  = mPosGround

deltaAngleZ = 0.05*pi/nBodies
p0 = np.array([0,0,0])

#create a chain of bodies:
for i in range(nBodies):
    
    A = RotationMatrixZ(i*deltaAngleZ)
    deltaRot2 = RotationMatrixZ(0.5*deltaAngleZ)
    p0 = p0 + A@[0.5*sx,0,0]

    omega0 = [0,0,0] #arbitrary initial angular velocity
    v0 = [0.,0.,0.] #initial translational velocity

    color=[1,0.1,0.1,1]

    oGraphics = graphics.Brick(centerPoint=[0, 0, 0], size=[sx, sy, sz], color=color)
 
    dictRB = mbs.CreateRigidBody(
                  inertia=RBinertia, 
                  referencePosition=p0, 
                  referenceRotationMatrix=A,
                  initialVelocity=v0,
                  initialAngularVelocity=omega0,
                  gravity=[0., 0., -9.81],
                  graphicsDataList=[oGraphics],
                  returnDict=True)
    [nRB, oRB] = [dictRB['nodeNumber'], dictRB['bodyNumber']]

    nodeList += [nRB]
    objectList += [oRB]
    lastDeltaRot2 = deltaRot2
    if i == 0:
         lastDeltaRot2 = RotationMatrixZ(0)
    #the joint frame is the markers': turned back on this body, as the end marker of the last body is turned forward
    mPos = mbs.AddMarker(MarkerBodyRigid(bodyNumber = oRB, localHT=exu.HT(rotation=lastDeltaRot2.T, translation=[-0.5*sx,0,0])))
        
    mbs.AddObject(GenericJoint(markerNumbers = [mPos, mPosLast], 
                               constrainedAxes=[1,1,1, 1,0,1],
                               visualization=VGenericJoint(axesRadius = 0.5*sy, axesLength=1.1*sz)))

    #marker for next chain body, turned for the joint to it
    mPosLast = mbs.AddMarker(MarkerBodyRigid(bodyNumber = oRB, localHT=exu.HT(rotation=deltaRot2, translation=[0.5*sx,0,0])))

    #add damping to bodies:
    mbs.AddObject(ObjectConnectorCartesianSpringDamper(markerNumbers = [mPosGround, mPosLast],
                                                       damping = [40]*3,
                                                       visualization=VCartesianSpringDamper(show=False)))
    
    p0 = p0 + A@[0.5*sx,0,0]

#activate by keypress 'D':
mbs.variables['activateMouseDrag'] = True
if activateWithKeyPress:
    mbs.variables['activateMouseDrag'] = False
    
def UFmouseDrag0(mbs, t, itemIndex, u, v, k, d, offset): #changed 2023-01-21:, mu, muPropZone):
    if not mbs.variables['activateMouseDrag'] == True:
        return 0
    p = SC.renderer.GetMouseCoordinates(True)
    p = SC.renderer.GetState()['openGLcoordinates']
    #print("u=",u)
    return k*(Ltot-0.5*sx+u-p[0]) + d*v

def UFmouseDrag1(mbs, t, itemIndex, u, v, k, d, offset): #changed 2023-01-21:, mu, muPropZone):
    if not mbs.variables['activateMouseDrag'] == True:
        return 0
    p = SC.renderer.GetMouseCoordinates(True)
    return k*(u-p[1]) + d*v

def UFmouseDrag2(mbs, t, itemIndex, u, v, k, d, offset): #changed 2023-01-21:, mu, muPropZone):
    if not mbs.variables['activateMouseDrag'] == True:
        return 0
    p = SC.renderer.GetMouseCoordinates(True)
    return k*(u-p[1]) + d*v

if True:
    nGround = mbs.AddNode(NodePointGround())
    mGroundCoordinate = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nGround, coordinate = 0))
    k=5.*1e4
    mCoord0 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nodeList[-1], coordinate = 0))
    mCoord1 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nodeList[-1], coordinate = 1))
    mCoord2 = mbs.AddMarker(MarkerNodeCoordinate(nodeNumber=nodeList[-1], coordinate = 2))
    
    mbs.AddObject(CoordinateSpringDamper(markerNumbers=[mGroundCoordinate, mCoord0], 
                                         stiffness=k, damping=0.01*k, 
                                         springForceUserFunction=UFmouseDrag0,
                                         visualization=VCoordinateSpringDamper(show=False),
                                        ))
    mbs.AddObject(CoordinateSpringDamper(markerNumbers=[mGroundCoordinate, mCoord2], 
                                         stiffness=k, damping=0.01*k, 
                                         springForceUserFunction=UFmouseDrag2,
                                         visualization=VCoordinateSpringDamper(show=False),
                                        ))

mbs.Assemble()
#exu.Print(mbs)

simulationSettings = exu.SimulationSettings() #takes currently set values or default values

tEnd = 10000
h = 0.001
simulationSettings.timeIntegration.numberOfSteps = int(tEnd/h)
simulationSettings.timeIntegration.endTime = tEnd
simulationSettings.solution.file.write = False
simulationSettings.solution.file.writePeriod = simulationSettings.timeIntegration.endTime/1000
simulationSettings.timeIntegration.verboseMode = 1

#good for interactive examples, as it is independent of CPU power ...
simulationSettings.timeIntegration.realtime.active = True
simulationSettings.linearSolver.solverType = exu.LinearSolverType.EigenSparse

simulationSettings.timeIntegration.newton.absoluteTolerance = 1e2 #if no force acts
simulationSettings.timeIntegration.newton.useModifiedNewton = True
simulationSettings.timeIntegration.generalizedAlpha.spectralRadius = 0.5 #0.6 works well 

simulationSettings.solution.file.information = "mouse interaction example: press 'D' to (de-)activate mouse drag, F2 to switch key functionality"

#+++++++++++++++++++++++++++++++++++
#these options are not necessary:
SC.visualizationSettings.nodes.defaultSize = 0.025
SC.visualizationSettings.nodes.drawNodesAsPoint = False
SC.visualizationSettings.nodes.showBasis = False

SC.visualizationSettings.openGL.light0.position = [0.2,0.2,10,0]

SC.visualizationSettings.openGL.light1.position = [1,1,-10,0]
SC.visualizationSettings.openGL.light1.diffuse= 0.5 #0.4
SC.visualizationSettings.openGL.light1.specular= 0.6 #0.4
SC.visualizationSettings.openGL.light1.enable = True

SC.visualizationSettings.openGL.advanced.lightModelTwoSide= True

SC.visualizationSettings.view0.scene.drawWorldBasis= True
SC.visualizationSettings.general.graphicsUpdateInterval = 0.01

SC.visualizationSettings.openGL.multiSampling = 4
SC.visualizationSettings.openGL.lineWidth = 2
SC.visualizationSettings.interactive.ignoreKeys = True #otherwise keyPressUserFunction not called!
SC.visualizationSettings.general.useMultiThreadedRendering = True

useGraphics = True
if useGraphics:
    SC.renderer.Start()
    if not SC.renderer.RestoreSavedState(): #no view saved yet: start from this one
        renderState = {'centerPoint': [-0.33064934611320496,
                         -0.5762133598327637,
                         0.41875001788139343],
                        'maxSceneSize': 1.75,
                        'zoom': 4.042552471160889,
                        'currentWindowSize': [1024, 768],
                        'modelRotation': [[1.0, 0.0, 0.0],
                         [0.0, -4.371138828673793e-08, -1.0],
                         [0.0, 1.0, -4.371138828673793e-08]],
                        'mouseCoordinates': [713.0, 379.0],
                        'openGLcoordinates': [1.7853742130100727, -0.5235759578645229]}
        SC.renderer.SetState(renderState)
    SC.renderer.DoIdleTasks()

#+++++++++++++++++++++++++++++++++++
#react on key press, in development state:
#causes crash at termination of python code ...
def UFkeyPress(key, action, mods):
    #print('key:',key)
    if chr(key) == 'D' and action == 1: #use capital letters for comparison!!! action 1 == press
        mbs.variables['activateMouseDrag'] = not mbs.variables['activateMouseDrag']
    
if activateWithKeyPress:
    SC.visualizationSettings.interactive.keyPressUserFunction = UFkeyPress


mbs.SolveDynamic(simulationSettings)
SC.visualizationSettings.interactive.keyPressUserFunction = 0

if useGraphics:
    SC.renderer.Stop() #safely close rendering window!
```