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Virtual EnvironmentsVirtual Environments

ELG5124/CSI5151 ELG5124/CSI5151 –– Fall 2011Fall 2011

JochenJochen LangLang

SITE, University of OttawaSITE, University of Ottawa

CanadaCanada

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Introduction to CHAI3D Introduction to CHAI3D

HapticsHaptics SDKSDK•• computer computer hapticshaptics

–– interface to different hardware, extensible (see interface to different hardware, extensible (see assignment 3)assignment 3)

–– hapticshaptics rendering looprendering loop

–– haptichaptic effectseffects

•• visualizationvisualization

–– graphics support based on graphics support based on openGLopenGL and GLUTand GLUT

–– visual rendering loopvisual rendering loop

–– scenegraphscenegraph

•• interactive realinteractive real--time simulationtime simulation

–– collision detection, timers and thread managementcollision detection, timers and thread management

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Overview: Overview: HapticHaptic Control LoopsControl Loops

User ControlUser Control ActuatorsActuators

Device +Device +

BiomechanicsBiomechanics

HapticHaptic

RenderingRendering

ForceForce

PositionPositionPositionPosition

ForceForce

Input LoopInput Loop

Output LoopOutput Loop

Adapted from M.C. Lin and M.A. Adapted from M.C. Lin and M.A. OtaduyOtaduy, Recent advances in , Recent advances in haptichaptic rendering and applications, rendering and applications,

SIGGRAPH course notes, 2005.SIGGRAPH course notes, 2005.

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HapticHaptic Rendering Rendering

HapticHaptic

RenderingRendering

PositionPositionForceForce

Collision Collision

DetectionDetectionObject Object

ResponseResponseForce Force

ComputationComputation

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Generic Generic HapticHaptic Devices Devices ––

Key MethodsKey Methods

class cGenericHapticDevice : public cGenericDevice

// Read the position of the device. Units are meters [m].int getPosition(cVector3d& a_position) // Read the orientation frame of the device end-effector.int getRotation(cMatrix3d& a_rotation)

// Read the linear velocity of the device. Units are meters per second [m/s].int getLinearVelocity(cVector3d& a_linearVelocity) // Read the angular velocity of the device. Units are in radians per second [m/s].int getAngularVelocity(cVector3d& a_angularVelocity)

// Send a force [N] to the haptic device.int setForce(cVector3d& a_force) // Read a sensed force [N] from the haptic device.int getForce(cVector3d& a_force) // Send a torque [N*m] to the haptic device.int setTorque(cVector3d& a_torque)// Read a sensed torque [N*m] from the haptic device.int getTorque(cVector3d& a_torque)

// read the status of the user switch [\b true = \b ON / \b false = \b OFF].int getUserSwitch(int a_switchIndex, bool& a_status) // Get the specifications of the current device.cHapticDeviceInfo getSpecifications()

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Generic Generic HapticHaptic Devices Devices ––

StateState

class cGenericHapticDevice : public cGenericDevice

// Open connection to haptic device (0 indicates success).

int open()

// Close connection to haptic device (0 indicates success).

int close()

// Initialize or calibrate haptic device (0 indicates success).

int initialize(const bool a_resetEncoders=false)

// Get the specifications of the current device

cHapticDeviceInfo getSpecifications()}

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HapticHaptic Device HandlerDevice Handler

class class cHapticDeviceHandlercHapticDeviceHandler

// Returns the number of devices connected to your computer.// Returns the number of devices connected to your computer.

unsigned unsigned intint getNumDevicesgetNumDevices() ()

// Updates information regarding the devices that are connected // Updates information regarding the devices that are connected to your to your computer.computer.

void update();void update();

// Returns the specifications of the // Returns the specifications of the ithith device.device.

intint getDeviceSpecificationsgetDeviceSpecifications((

cHapticDeviceInfocHapticDeviceInfo& & a_deviceSpecificationsa_deviceSpecifications, ,

unsigned unsigned intint a_indexa_index = 0);= 0);

// Returns a handle to the // Returns a handle to the ithith device if available.device if available.

intint getDevice(cGenericHapticDevicegetDevice(cGenericHapticDevice*& *& a_hapticDevicea_hapticDevice, ,

unsigned unsigned intint a_indexa_index = 0); = 0);

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Connecting to a Connecting to a haptichaptic devicedevice

// create a haptic device handler

handler = new cHapticDeviceHandler();

// get access to the first available haptic device

cGenericHapticDevice* hapticDevice;

handler->getDevice(hapticDevice, 0);

// retrieve information about the current haptic device

cHapticDeviceInfo info= hapticDevice->getSpecifications();

cHapticDeviceInfo

string m_manufacturerName;

double m_maxForce;

double m_workspaceRadius;

bool m_sensedPosition;

bool m_sensedRotation;

bool m_actuatedPosition;

bool m_actuatedRotation;

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Chai3D Source File OrganizationChai3D Source File Organization

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ScenegraphScenegraph NodesNodes

cGenericObjectcGenericObject

•• Parent of all Parent of all scenegraphscenegraph nodesnodes

cCameracCamera

•• Controls the position/orientation of Controls the position/orientation of the camera relative to the scenethe camera relative to the scene

cLightcLight

•• Light source position and Light source position and orientationorientation

cMeshcMesh, , cShapeSpherecShapeSphere, etc., etc.

•• Objects in the sceneObjects in the scene

cGenericToolcGenericTool

•• HapticHaptic toolstools

cWorldcWorld

•• Root of the sceneRoot of the scene

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HapticHaptic ScenegraphScenegraph TraversalTraversal

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Example: 12Example: 12--PolygonPolygon

•• Uses a triangle meshUses a triangle mesh

•• HapticHaptic finger proxy rendering finger proxy rendering algorithm of [algorithm of [RuspiniRuspini et al. et al. ’’97]97]

•• Collision detection with build in Collision detection with build in axisaxis--alignedaligned--boundingbounding--box treebox tree

©© Copyright Chai3DCopyright Chai3D

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Credits, ReferencesCredits, References

Material from:Material from:

•• Francois Conti, Chai3D source codeFrancois Conti, Chai3D source code

•• Kenneth Salisbury, Federico Kenneth Salisbury, Federico BarbagliBarbagli and Franand Franççois ois Conti, CS 277 Conti, CS 277 -- Experimental Experimental HapticsHaptics, Lecture 4, , Lecture 4, ““Open Source Framework CHAI 3DOpen Source Framework CHAI 3D””, Stanford , Stanford UniversityUniversity