Electrical and Computer Engineering Dept

Electrical and Computer Engineering Dept.

VR PROGRAMMING

System architecture

VR ToolkitsVR Toolkits

VR Programming ToolkitsVR Programming Toolkits Are extensible libraries of object-oriented functions designed to help the VR developer; Support various common i/o devices used in VR (so drivers need not be written by the developer); Allow import of CAD models (saves time), editing of shapes, specifying object hierarchies, collision detection and multi-level of detail, shading and texturing, run-time management; Have built-in networking functions for multi-user interactions, etc.

VR Toolkits can be classified by:VR Toolkits can be classified by: Whether text-based or graphical-programming; The type of language used and the library size; The type of i/o devices supported; The type of rendering supported; Whether general-purpose or application specific; Whether proprietary (more functionality, better documented) or public domain (free, but less documentation and functionality)

VR Toolkits in Early ‘90sVR Toolkits in Early ‘90s RenderWare (Cannon), VRT3/Superscape (Dimension Ltd.), Cyberspace Developer Kit (Autodesk), Cosmo Authoring Tool (SGI/Platinum/CA), Rend386 and others; They allowed either text-based programming (RenderWare, CDK and Rend386), or graphical programming (Superscape and Cosmo); They were platform-independent and generally did not require graphics acceleration hardware; As a result they tended to use “low-end” I/o devices (mouse) and to support flat shading to maintain fast rendering.

Rend386 sceneRend386 scene

VR Toolkits discussed in this chapterVR Toolkits discussed in this chapterName Application Proprietary Library size language

Java3D

(Sun Microsystems)

General Purpose no Implemented in C

Programming in Java

19 packages, 275 classes

Vizard Toolkit and

PeoplePak (WorldViz)

General Purpose

avatar extension

yes OpenGL-based

Python scripting language

GHOST (SensAble Technologies)

Haptics for Phantom

yes C++C++

PeopleShop

(Boston Dynamics)

Military/civilian yes C/C++C/C++

3DGame Studio Game engine yes C++C++

The scene graph:The scene graph: Is a hierarchical organization of objects (visible or not) in the virtual world (or “universe”) together with the view to that world; Scene graphs are represented by a tree structure, with nodes connected by branches. Visible objects are represented by external nodes, which are called leafs (they have no children). Example nodes F, G, H, I Internal nodes represent transformations (which apply to all their children)

A

B C

ED J

F G H I

Root nodeRoot node

Internal nodeInternal node

External nodeExternal node

palmpalm

SceneScene

BallBall

Scene graph shows that the ball is a child of “scene”

Scene graphs are not static

palmpalm

SceneScene

BallBall

Scene graph has been modified, such that the ball is now a child of the palm

VC 6.1 on book CD

Authoring Authoring (Modeling) (Modeling) StagesStages

Model GeometryModel Geometry

Define and link Define and link sensorssensors

Define action Define action functionsfunctions

Define scene graphDefine scene graph

Define networkingDefine networking

Run-time loopRun-time loop

Start SimulationStart Simulation

Update ObjectsUpdate Objects(from sensors and (from sensors and intelligent actionsintelligent actions

Render sceneRender scene(graphics, audio, (graphics, audio,

haptics)haptics)

Read Sensor DataRead Sensor Data

Exit SimulationExit Simulation

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me


Java3D

(Sun Microsystems)

General Purpose no Implemented in C

Programming in Java

19 packages, 275 classes

Vizard and


General Purpose

avatar extension

yes OpenGL-based



Haptics for Phantom

yes C++C++

PeopleShop

(Boston Dynamics)



Java and Java 3DJava and Java 3D Java

object oriented programming language developed for network applications platform independence slower than C/C++

Java 3D Java hierarchy of classes that serves as an interface to 3D graphics rendering and sound rendering systems Perfectly integrated with Java Strong object oriented architecture Powerful 3D graphics API

Java 3D Java 3D InitiationInitiation


Setup sensorsSetup sensors

Define behaviorsDefine behaviors


NetworkingNetworking







Java 3D geometry:Java 3D geometry: Geometry can be imported from various file formats (e.g. 3DS, DXF, LWS, NFF, OBJ, VRT, VTK, WRL) Can be created as a primitive geometry (e.g. sphere, cone, cylinder, …) Custom geometry created by specifying the vertices, edges, normals, texture coordinates using specially defined classes

Imported geometryImported geometryloader.load(“Hand.wrl")loader.load(“Hand.wrl")

Geometry primitive:Geometry primitive:new Sphere(radius)new Sphere(radius)

Custom geometry:Custom geometry:new GeometryArray(…)new GeometryArray(…)new LineArray(…)new LineArray(…)new QuadArray(…)new QuadArray(…)new TriangleArray(…)new TriangleArray(…)

Java 3D object Java 3D object appearance:appearance: The appearance of a geometry is specified using an appearance object An appearance-class object stores information about the material (diffuse, specular, shininess, opacity, …) and texture

Mat = new Material();Mat.setDiffuseColor(r, g, b);Mat.setAmbientColor(r, g, b);Mat.setSpecularColor(r, g, b);

TexLd = new TextureLoader(“checkered.jpg”, ...);Tex = TexLd.getTexture();

Appr = new Appearance();Appr.setMaterial(Mat);Appr.setTexture(Text);

Geom.setAppearance(Appr)







Java3D node types:Java3D node types:

Node

Group

Leaf

BranchGroup

TransformGroup

Switch

Background

Behavior

Fog

Light

Shape3D

Compilable sub-graph

Transform + child nodes

Select which of the children are visible (useful for LOD)

Universe background. Can be a color or an image

Actions to be performed by the simulation

Fog node

Light node. Special derived classes: AmbientLight, PointLight, DirectionalLight

Geometry + Appearance + BoundingBox

Java3D scene graphJava3D scene graph

Node

Loading objects from filesLoading objects from files

Java3D offers by default support for Lightwave and Wavefront model files Loaders for other file formats can be downloaded for free from the web http://www.j3d.org/utilities/loaders.html Loaders add the content of the read file to the scene graph as a single object. However, they provide functions to access the subparts individually

Universe Universe RootRoot

CubeCube SphereSphere HandHand

ThumbThumb IndexIndex MiddleMiddle RingRing SmallSmall

Scene Sc = loader.load(“Hand.wrl”);BranchGroup Bg = Sc.getSceneGroup();RootNode.addChild(Bg);

Java3D model loadingJava3D model loading

Scene Sc = loader.load(“Hand.wrl”);BranchGroup Bg = Sc.getSceneGroup();Thumb = Bg.getChild(0);Index = Bg.getChild(1);Middle = Bg.getChild(2);Ring = Bg.getChild(3);Small = Bg.getChild(4);

Adding the model to the scene graph

Accessing subparts of the loaded model

Palm = loader.load("Palm.wrl").getSceneGroup();ThumbProximal = loader.load("ThumbProximal.wrl").getSceneGroup();ThumbDistal = loader.load("ThumbDistal.wrl").getSceneGroup();IndexProximal = loader.load("IndexProximal.wrl").getSceneGroup();IndexMiddle = loader.load("IndexMiddle.wrl").getSceneGroup();IndexDistal = loader.load("IndexDistal.wrl").getSceneGroup();MiddleProximal = loader.load("MiddleProximal.wrl").getSceneGroup();MiddleMiddle = loader.load("MiddleMiddle.wrl").getSceneGroup();MiddleDistal = loader.load("MiddleDistal.wrl").getSceneGroup();RingProximal = loader.load("RingProximal.wrl").getSceneGroup();RingMiddle = loader.load("RingMiddle.wrl").getSceneGroup();RingDistal = loader.load("RingDistal.wrl").getSceneGroup();SmallProximal = loader.load("SmallProximal.wrl").getSceneGroup();SmallMiddle = loader.load("SmallMiddle.wrl").getSceneGroup();SmallDistal = loader.load("SmallDistal.wrl").getSceneGroup();

Java3D virtual hand loading:Java3D virtual hand loading:

Java3D virtual hand hierarchy:Java3D virtual hand hierarchy:

Palm.addchild(ThumbProximal );Palm.addchild(ThumbProximal );ThumbProximal .addchild(ThumbDistal );ThumbProximal .addchild(ThumbDistal );

Palm.addchild(IndexProximal );Palm.addchild(IndexProximal );IndexProximal .addchild(IndexMiddle );IndexProximal .addchild(IndexMiddle );IndexMiddle .addchild(IndexDistal );IndexMiddle .addchild(IndexDistal );

Palm.addchild(MiddleProximal );Palm.addchild(MiddleProximal );MiddleProximal .addchild(MiddleMiddle );MiddleProximal .addchild(MiddleMiddle );MiddleMiddle .addchild(MiddleDistal );MiddleMiddle .addchild(MiddleDistal );

Palm.addchild(RingProximal );Palm.addchild(RingProximal );RingProximal .addchild(RingMiddle );RingProximal .addchild(RingMiddle );RingMiddle .addchild(RingDistal );RingMiddle .addchild(RingDistal );

Palm.addchild(SmallProximal );Palm.addchild(SmallProximal );SmallProximal .addchild(SmallMiddle );SmallProximal .addchild(SmallMiddle );SmallMiddle .addchild(SmallDistal );SmallMiddle .addchild(SmallDistal );

Java3D Java3D InitiationInitiation






Input devices in Java3DInput devices in Java3D

The only input devices supported by Java3D are the mouse and the keyboard The integration of the input devices currently used in VR applications (position sensors, track balls, joysticks, sensing gloves…) relies entirely on the developer Usually the drivers are written in C/C++. One needs either to re-write the driver using Java or use JNI (Java Native Interface) to call the C/C++ version of the driver. The latter solution is more desirable. Java3D provides a nice general purpose input device interface that can be used to integrate sensors. However, many times developers prefer custom made approaches

Java3D General purpose sensor interfaceJava3D General purpose sensor interfaceclass PhysicalEnvironment - stores information about all the input devices and sensors involved in the simulation

class InputDevice - interface for an input device driver

class Sensor - class for objects that provide real time data

PhysicalEnvironment

InputDevices Sensors

One input device can provide one or more sensorsOne input device can provide one or more sensors

A sensors object needs not be in relation with an input device (VRML style sensors)A sensors object needs not be in relation with an input device (VRML style sensors)




Animating the sceneAnimating the scene



Java3D - Animating the simulationJava3D - Animating the simulation

Java3D offers Behavior objects for controlling the simulation A Behavior object contains a set of actions performed when the object receives a stimulus A stimulus is sent by a WakeupCondition object Some wakeup classes:

WakeupOnCollisionEntryWakeupOnCollisionExitWakeupOnCollisionMovementWakeupOnElapsedFramesWakeupOnElapsedTimeWakeupOnSensorEntryWakeupOnSensorExitWakeupOnViewPlatformEntryWakeupOnViewPlatformExit

Java3D - Behavior usageJava3D - Behavior usage

WakeupOnElapsedFrames Wup = new WakeupOnElapsedFrames(0);WakeupOnElapsedFrames Wup = new WakeupOnElapsedFrames(0);

Bhv.wakeupOn(Wup);Bhv.wakeupOn(Wup);

Universe Universe RootRoot

• We define a behavior We define a behavior Bhv Bhv that rotates the that rotates the sphere by 1 degreesphere by 1 degree

• We want this behavior to be called each We want this behavior to be called each frame so that the sphere will be spinningframe so that the sphere will be spinning

VC 6.3 on book CD VC 6.4 on book CD

The Java 3D View object describes the graphics display used in the simulation, as well as the user’s position versus that display (given by the tracker);

The View model provides a separation between the virtual world provided by the ViewPlatform node and the real I/O devices used in the interaction; This separation helps portability.

Several users that are tracked can be mapped to the same location in the virtual world. This corresponds to several Views and a single ViewPlatform;

Conversely, a single user can control several ViewPlatforms;

This corresponds to several Views since each ViewPlatform has its own View; Thus a single user can have several Views to a virtual world, and can “teleport” between them. Thus a single user can have several Views to a virtual world, and can “teleport” between them.

View platform 1View platform 1View platform 2View platform 2







Java3D Java3D simulationsimulation

Java Java ApplicationApplication


Java Java AppletApplet


Java Java ApplicationApplication

Java3D - NetworkingJava3D - Networking Java3D does not provide a built-in solution for networked virtual environments However, it’s perfect integration in the Java language allows the developer to use the powerful network features offered by Java Java3D applications can run as stand alone applications or as applets in a web browser


Java Java AppletApplet

Server

Java3D and VRMLJava3D and VRML

VRML provides possibilities for defining the objects and animating the objects in a virtual world Graphics APIs such as Java3D or WTK load from a VRML file only the static information, ignoring the sensors, routes, scripts, etc. Java3D structure is general enough to make the import of sensors and routes possible but currently we are not aware of any loader that does it One of the most popular library of Java3D loaders is the NCSA Portfolio (http://www.ncsa.uiuc.edu/~srp/Java3D/portfolio/)

NCSA PortfolioNCSA Portfolio

Offers loaders for several model files

3D Studio (3DS) TrueSpace COB loader (COB) Java 3D Digital Elevation Map (DEM) AutoCAD (DXF ) Imagine (IOB) Lightwave (LWS) Sense8 (NFF ) Wavefront (OBJ) Protein Data Bank (PDB) Visualization Toolkit (VTK) VRML97

Loades the following parts of VRML97 files

Appearance Box Coordinate Collision (for grouping only) Group IndexedFaceSet IndexedLineSet Material Normal Shape Sphere Transform

Java3D on-line resources

http://java.sun.com/products/java-media/3D/index.html http://www.j3d.org http://www.ncsa.uiuc.edu/~srp/Java3D/portfolio/

Comparison between Java3D and WTKComparison between Java3D and WTK

A comparative study was done at Rutgers between Java3d (Version 1.3beta 1) and WTK (Release 9); The simulation ran on a dual Pentium III 933 MHz PC (Dell) with 512 Mbytes RAM, with an Wildcat 4110 graphics accelerator which had 64 Mbytes RAM; The I/o interfaces were a Polhemus Insidetrack or the Rutgers Master II force feedback glove; The scene consisted of several 420-polygon spheres and a virtual hand with 2,270 polygons; The spheres rotated constantly around an arbitrary axis, while the hand was either rotating, or driven by the user.

Java3D –WTK ComparisonGraphics scene used in experimentsGraphics scene used in experiments

Comparison between Java3D and WTKComparison between Java3D and WTK

The simulation variables used to judged performance were: graphic mode (monoscopic, stereoscopic), rendering mode (wireframe, Gouraud, textured); scene complexity (number of polygons 5,000 – 50,000); lighting (number of light sources 1, 5, 10); interactivity (no interaction, hand input, force feedback)

Java3D –WTK Comparison

Java3d is faster on average than WTK, but has higher variability

Java3D –WTK Comparison

Java3d Release 3.1 Beta 1 has less system latencies than WTK Release 9

But Java3d has more variability in the scene rendering time

WTK does not have spikes in the scene rendering time


Java3D

(Sun Microsystems)

General Purpose no Implemented in CImplemented in C

Programming in JavaProgramming in Java

19 packages, 275 classes19 packages, 275 classes

Vizard and


General Purpose

avatar extension

yes OpenGL-based



Haptics for Phantom

yes C++C++

PeopleShop

(Boston Dynamics)



Vizard characteristics:Vizard characteristics: Uses Python which is a scalable and cross-platform; It is object-oriented and simple to integrate with C/C++ It runs on Unix, Windows, Mac and other platforms; Uses a 4-window “workbench” which allows programmers to write and execute code, inspect 3D models, drag-and-drop objects, and issue commands while the scene is being rendered.

Stack of scripts – errors are highlighted as you type

Interactive window – input commands

Resource window – Text list of word assets

3D window – Explore individualobjects

Workbench use:Workbench use:Icon menu

Scene exploration with the mouse

Importing objects

import vizimport handviz.go()#Identify the 5DT glove's port.PORT_5DT_USB = 0

#Add the 5DT sensorsensor = viz.add('5dt.dls')

#Create a hand object from the data gloveglove = hand.add(sensor,hand.GLOVE_5DT)

#Place the hand in front of the userglove.translate(0,1,5)glove.rotate(180,-90,180) # now when you run the script the glove should be moving

Vizard virtual hand:Vizard virtual hand:

import vizviz.go()

logo = viz.add('logo.wrl') #add vizard logo and place it in front of userlogo.translate(0,2,4)

tex1 = viz.add('gb_noise.jpg') #add two textures that will then be applied to the logo#tex2 = viz.add('brick.jpg')logo.texture(tex1) #applies the first texturelogo.texture(tex2,'',1) #applies the second texture to the logoblend = viz.add('multitexblend.fp') #indicate how to blend the two textureslogo.apply(blend)

Vizard multi-texturing:Vizard multi-texturing:

Vizard Simulation Servers:Vizard Simulation Servers: More than one user can inhabit the same environment. Each user needs to run Vizard. After the world is set up, each user has to set up two “mail boxes”. One receives information from the other user after it was given network name. Messages come in sequence [0] who sent it, [1] what is sent, [2] and larger the actual data

User 2User 2User 1User 1

Position is the propertyPosition is the property

Ball is the objectBall is the object

action

information

Vizard networking example:Vizard networking example:Import vizViz.go()Ball=viz.add(‘ball.wrl’) #create a Ball object that is controlled by the other user #add the world that will be displayed on your computer #Use a prompt to ask the other user the network name of his computer.target_machine = viz.input('Enter the name of the other machine'). upper()

#Add a mailbox from which to send messages to the other user. This is your outbox.target_mailbox = viz.add(viz.NETWORK, target_machine) #Add an id for the timer.BROADCAST = 1

#Add the timer.def mytimer(num): if num == BROADCAST: #Retrieve your current position. position = viz.get(viz.HEAD_POS) #Send the data to the target mailbox. All the recipient will get your yaw, x and z coordinates. target_mailbox.send(position[0], position[1], position[2])

Vizard networking example:Vizard networking example:

##This function will deal with incoming messages.def mynetwork(message): #message[0] is who sent the message, message[1] is a description of what he #sent and message[2] and greater are the messages themselves. x = message[2] y = message[3] z = message[4] ball.translate(x,y,z)

# Callback the network function to await incoming messages.viz.callback(viz.NETWORK_EVENT, mynetwork)# Callback the timer. viz.callback(viz.TIMER_EVENT, mytimer)# Start the timer.viz.starttimer(BROADCAST, 0.01, -1)


Java3D

(Sun Microsystems)




Vizard and


General Purpose

avatar extension

yes OpenGL-based



Haptics for Phantom

yes C++C++

PeopleShop

(Boston Dynamics)



GHOST Toolkit for the PHANToMGHOST Toolkit for the PHANToM Provides realistic haptic interaction

Provides and intuitive interfaces to haptics

Provides a haptic scene graph aligned with 3D graphics APIs

Provides an extensible environment for extending haptic interaction technologies

Point haptic interaction with PHANTOM

geometry based on user defined force models

Geometry moves dynamically in response to forces

x

y

z(0,0,0)

PHANToM Desktop modelPHANToM Desktop model

GHOST – Application interactionGHOST – Application interaction

x

y

z (0,0,0)

adapted from Ghost SDK Programmer’s Guide (version 3.1)

Application ProcessApplication Process Haptic ProcessHaptic Process

Scene CreationScene Creation

Collision detectionCollision detectionCollision responseCollision response

Haptic State Haptic State UpdateUpdate

Clean-upClean-up

HapticHapticRenderingRendering

HapticHapticServo loopServo loop

30 f

ps

30 f

ps Scene RenderingScene Rendering

1000 Hz1000 Hz

The GHOST haptics scene graphThe GHOST haptics scene graph

x

y

z (0,0,0)






Clean-upClean-up



30 f

ps

30 f


1000 Hz1000 Hz

Haptic scene graphHaptic scene graph Provides a structured way to construct a haptic scene, including geometry and dynamics;

is traversed only from top to bottom (unlike WTK);

each node reachable by only one (unique) traversal from the root (a child node has only one parent node)

Each node has its own transform (no separate transform nodes);

cannot use pointers to repeat instances of the same object, since similar objects have different haptic interactions;

Separator nodes to create a hierarchy – Transforms on the Separator affect its sub-tree;

GHOST node classesGHOST node classes

3D supportStatic NodesDynamic NodesUtility Classes

gstBoundedHapticObjgstNode gstTransform gstShape

gstCube

gstSphere

gstCone

gstCylinder

gstTorus

gstTriPolyMeshHaptic

gstPHANToM_SCP

gstBoundary

gstBoundaryCube

gstSeparator gstDynamic gstDial

gstButton

gstSlider

gstPHANToM

gstPHANToMDynamic

gstPHANToMTranslation

gstPHANToMRotation

gstRigidBody

gstForceField

gstConstantForceField

gstPoint gstVector

gstTransformMatrix

gstEffect gstInertiaEffect

gstBuzzEffect

gstConstraint

gstManipulator gstTranslateManip

gstRotateManip

gstScaleManip

gstSpatialObject

gstSpatialPartition

gstPlane

gstTriPolyMeshBase

gstTriPolyBase

gstTriPoly

gstBinTree

gstTriPolyMesh

GHOST nine node classesGHOST nine node classes

GHOST nine node classes (continued)GHOST nine node classes (continued)

GHOST nine node classes (continued)GHOST nine node classes (continued)

Scene graph exampleScene graph example

y

xz

Head

y

xz

Left Shoulder

y

xz

Right Shouldery

xz

Right Elbow

y x

zLeft Elbow

y

xz

Torso

y

xz

Body

Static scene graph – only separators and geometry nodes as leavesStatic scene graph – only separators and geometry nodes as leaves

GHOST code example:GHOST code example: #include <stdlib.h>#include <stdlib.h>#include <gstBasic.h>#include <gstBasic.h>#include <gstSphere.h>#include <gstSphere.h>#include <gstPHANToM.h>#include <gstPHANToM.h>#include <gstSeparator.h>#include <gstSeparator.h>#include <gstScene.h>#include <gstScene.h>

Main()Main()gstScene *scene = new gstScene;gstScene *scene = new gstScene;gstSeparator *root = new gstSeparator;gstSeparator *root = new gstSeparator;gstSphere *sphere = new gstSphere;gstSphere *sphere = new gstSphere;

Sptere -> setRadius(20);Sptere -> setRadius(20);gstPHANToM *phantom = new gstPHANToM (``PHANToM name``);gstPHANToM *phantom = new gstPHANToM (``PHANToM name``);Root -> addChild(phantom);Root -> addChild(phantom);Root-> addChild(sphere);Root-> addChild(sphere);Scene-> setRoot(root);Scene-> setRoot(root);Scene -> startServoLoop();Scene -> startServoLoop();

While(!scene -> getDoneServoLoop()) While(!scene -> getDoneServoLoop()) // end application by calling scene -> stopServoLoop ();// end application by calling scene -> stopServoLoop ();

Force calculation and dynamicsForce calculation and dynamics

x

y

z (0,0,0)






Clean-upClean-up



30 f

ps

30 f


1000 Hz1000 Hz

Collision detection and responseCollision detection and response

The scene graph contains at least one representation of the haptic interface through gstPHANToM node. There can be up to four such nodes (four haptic interfaces in one haptic scene)

Collisions are detected between this node and the geometry nodes through the gstShape node that goes from “untouched” to “touched”;

When collision exists, the gstPHANToM_SCP (surface contact point) is added to the scene graph. This node should be added to the scene graph under the same parent as gstPHANToM node.

Collision detection and responseCollision detection and response

Normal ForceNormal Force (depends on spring(depends on springand damper coefficients)and damper coefficients)

Friction ForceFriction Force (depends on static and dynamic (depends on static and dynamic friction coefficients)friction coefficients)

Forces are calculated following collision;

Collision response through dynamic effects (movable nodes, solid body dynamics);

Application informed if needed (user defined).

Dynamic nodesDynamic nodes

The gstDynamic node adds movement ability to the geometry nodes beneath it. A subtree under a gstDynamic node represents one physically dynamic object.

Forces generated by gstPHANToM node colliding with one of the geometries of such object are added to the state of the gstDynamic node

Transformations (rotations, translations) are always applied to the gstDynamic node, not its children;

It has four derived classes gstDial, gstButton, gstSlider and gstRigidBody.

Dynamic nodes (continued)Dynamic nodes (continued) When a gstDynamic node changes state, an event is generated which calls a user-defined callback function.

Example – the application may quit if a gstButton changes state from pressed to released.

gstButton gstButton behavioral examplebehavioral example

Updating the applicationUpdating the application

x

y

z (0,0,0)






Clean-upClean-up



30 f

ps

30 f


1000 Hz1000 Hz

Graphics and event callbacksGraphics and event callbacks The user selects which nodes have call-back functions, and what information needs to be sent back to the application;

This way the application calls updateGraphics to have graphics information updated. Nodes that have a graphics call-back defined, and have a new state since the last call to updateGraphics will copy their current state to a defined data structure

Call-backs pass new state information of the haptic scene nodes from GHOST haptics process to the application process;

For example, the user can create a callback for the graphics representation of the position of the gstPHANToM node. This should change to callback of gstPHANToM_SCP after collision, so the user can see the location of the contact point on the object.

Mapping the user to the haptic scene Mapping the user to the haptic scene

Phantom workspacePhantom workspace

User workspaceUser workspace

Camera mapping to PHANToM workspaceCamera mapping to PHANToM workspace

Camera

Phantom workspace

z-axis

Phantom

workspac

e

Camera

Phantom

workspac

e

phantomSepphantomSepTransform M Transform M rotationrotation

phantomSepphantomSepTransform M Transform M cameracamera

phantomSepphantomSepTransform M Transform M zaxisOffsetzaxisOffset

from Ghost SDK Programmer’s Guide (version 3.1)

Scaling camera and PHANToM workspacesScaling camera and PHANToM workspaces

Camera workspaceCamera workspacetoo largetoo large

Camera workspaceCamera workspacetoo smalltoo small

Camera workspace Camera workspace appropriateappropriate

Camera

Phantom workspace

Camera

Phantom workspace

Camera

Phantom workspace


Camera

Dxmax Dphantomxmax

The scale factor depends on the distance Dxmax from the focal point to the frustum

The distance Dphantomxmax from the non-scaled PHANTOM workspace center to the side limit must also be determined

The scale factor is then Sfrustum=Dxmax/Dphantomxmax


To maintain haptic fidelity, the gstShape node physical properties (compliance and damping) need to be scaled too;

SurfaceKspringnew = SurfaceKspringcurrent/Sfrustum

SurfaceKdampingnew = SurfaceKdampingcurrent/Sfrustum

where SurfaceKspring and SurfaceKdamping are gstShape compliance and damping coefficients.


Java3D

(Sun Microsystems)




Vizard and


General Purpose

avatar extension

yes OpenGL-based



Haptics for Phantom

yes C++C++

PeopleShop

(Boston Dynamics)



BDI PeopleShop/DI-Guy characteristicsBDI PeopleShop/DI-Guy characteristics Provides a realistic way to simulate human characters in real-time scenes without using tracking suits;

Is a task-level programming environment combined with a menu-based GUI;

Tasks are mapped to pre-defined (stored) joint motions which are interpolated in real time;

Well-suited for Distributed Interactive Simulations (DIS) due to low bandwidth requirements and live reckoning;

Initially designed for the military, now extended to civilian applications, such as accident reenactment, architectural walk-through, driving simulators, police training, etc.

BDI PeopleShop/DI-Guy characteristics - continuedBDI PeopleShop/DI-Guy characteristics - continued

Linkable object library that runs on SGI, Intel PCs, as well as other platforms;

The library has modules for run-time motion engines, graphics display, motion data, 3D graphics models, textures, and network interfaces for DIS;

Runs under OpenGL, Direct3D, Mak Stealth and other packages;

Recommended hardware is Intel > 200MHz, 64 MB Ram, and graphics accelerator (for Open GL, OpenGVS or Direct3D).

PeopleShop PeopleShop InitiationInitiation

Scene GeometryScene Geometry

Define Define sensorssensors

Define Define behaviorbehavior

Define character Define character pathpath








PeopleShop Characters PeopleShop Characters

Are articulated polygonal structures with 54 DOF and 11 links;

Vehicles are also treated as characters;

Different types of characters have different acceptable actions;

Each type of character has different user-selectable appearances (ex. Character vehicle can be a tank or a police car, etc.);

Characters are textured to increase realism and reduce polygonal count

Character selectionCharacter selection

Character type determines acceptable actions (menu selectable)

Appearance selectionAppearance selection

Bob_shorts Bob_shorts Joe_blue Joe_blue Bridget_skirt Bridget_skirt Diane_teen Diane_teen

Character appearance (menu selectable)

BDI ToolkitsBDI Toolkits

Character level-of-detail segmentation based on distance to virtual camera improves real-time performance (up to about 100 characters can be in a scene)

38 polygons38 polygons

2500 polygons2500 polygons

Supplemental bdi.DI-Guy-LOD.mpg




Define Define BehaviorBehavior



PeopleShop path specificationPeopleShop path specification

PathPath

WaypointWaypoint

SlopeSlopeAdjuster Adjuster

Initial pathInitial path Extended pathExtended path Added waypointAdded waypoint

BDI ToolkitsBDI Toolkits

Action Action beadbead

End End bead bead

Stacked action Stacked action beadsbeads

Last action bead Last action bead

Editing actionsEditing actions

VC 6.6

on book CD

VC 6.5

on book CD



DefineDefinesensorssensors




BDI ToolkitsBDI ToolkitsSensor boundarySensor boundary

When soldier A enters the sensor volume, the system is notified – this triggers soldier B’s shooting of A

Soldier ASoldier A

Soldier Soldier BB

PeopleShop sensorsPeopleShop sensors

Sensors are user-defined volumes in space that detect when a character enters them

(PeopleShop User’s Manual)

Sensor boundarySensor boundary

Supplemental

bdi.farmhouse.mpg







PeopleShop BehaviorsPeopleShop Behaviors Behaviors can be reflex (based on signals received from sensors); Behaviors can also be specified with decision beads; Decision beads can be placed on the character’s path (colored red); The two parameters characterizing a decision bead are distance and length; Distance specifies how far from the start of the path the decision Bead is placed; Length indicates the distance from the beginning of the decision region that the decision bead is active; Decisions can be converted to script:

BDI ToolkitsBDI ToolkitsDecision clauses (IF/THEN/ELSE)

PeopleShop PeopleShop Run-timeRun-time

PeolpeShop PeolpeShop InitiationInitiation

Interactive TrainingInteractive Training Immersive TrainingImmersive TrainingScenario VisualizationScenario Visualization

User(s)User(s) User(s)User(s)User(s)User(s)

PeopleShop Run-timePeopleShop Run-time




BDI PeopleShop ToolkitBDI PeopleShop Toolkit

User is interacting in real time with the simulation using a joystick or mouseand menu. Limited control and immersion. Natural speeds should not be

exceeded.(from Koechling et al., 1997)

VC 6.7

PeopleShop PeopleShop Run-timeRun-time




BDI PeopleShop – Run time modesBDI PeopleShop – Run time modes

User is interacting in real time with the simulation using a trackers and sensors.Control is at the joint level and immersion is increased.

Omni-directional treadmillOmni-directional treadmill

Sensorized weaponSensorized weapon

(BDI, 1997)







PeopleShop Networking PeopleShop Networking

Updating human figures in DIS is much more bandwidth expensive than vehicles;

Vehicles have few degrees of freedom, while a human figures with 40 joints updated at 20 Hz require 800 packets/sec.;

Instead of updating every joint, PeopleShop only updates at the task level (action, position, velocity). It requires about two packets/sec to produce a smooth simulation;

Works well for large number of participants such as in dismounted infantry training.

Uses “live reckoning” vs. dead reckoning used previously for vehicles

BDI ToolkitsBDI ToolkitsClassical DIS using dead reckoningClassical DIS using dead reckoning

(from Koechling et al., 1997)

BDI ToolkitsBDI Toolkits DIS using live reckoning and human-in-the-loopDIS using live reckoning and human-in-the-loop

DI-Guy modelDI-Guy model DI-Guy modelDI-Guy model

Task-level change Task-level change (action, orientation, velocity)(action, orientation, velocity)

(from Koechling et al., 1997)

PeopleShop “Top Gun” PeopleShop “Top Gun” (courtesy Boston Dynamics Inc.)(courtesy Boston Dynamics Inc.)


Java3D

(Sun Microsystems)




Vizard and


General Purpose

avatar extension

yes OpenGL-based



Haptics for Phantom

yes C++C++

PeopleShop

(Boston Dynamics)



3D Game Studio characteristics3D Game Studio characteristics Provides an easy and fast way to program virtual worlds using the A6 game engine;

Is a a combination of task-level programming environment combined with a menu-based GUI and script programming for more flexibility;

Well-suited for multi-user simulations over LANs and WAN (TCP/IP and UDP);

Initially designed for the games, now extended to VR programming due to its functionality and price (various versions with increasing number of features, up to commercial license of about $500)

3D Game Studio characteristics3D Game Studio characteristics the 3D Engine allows multiple views (multiple virtual cameras) and is built around DirectX 9 graphics pipeline;

light sources are point, spot or directional

optimization is done through culling (Potential Visibility Set and frustrum);

further optimization through geometric LOD and texture detail

surface meshes are deformable, and objects have dynamics

character animations are done through bones (skeletons) and are blended.

3D Game Studio geometry creation3D Game Studio geometry creation

we can import from a large library of models, or a file created with another modeling tool like 3D Studio Max

or objects can be created using the World Editor (WED) 3D editor

3D Game Studio texturing3D Game Studio texturing

bump maps

light maps and multi-texturing (up to 8)

3D Game Studio character animation3D Game Studio character animation

animation can be imported if created in Maya, or characters can be created and animated using the model editor.

Frames are declared in order of action

Physics and Sound enginesPhysics and Sound engines collision detection is done at the polygon level and objects respect physical behavior like gravity, elasticity and friction

Cscript – a simplified version of C++ is used to create physics behavior through special functions, and to do I/O programming (keyboard keys and mouse)

static and dynamic 3D sound sources can be programmed

3D Game 3D Game Studio Studio InitiationInitiation

3D Game Studio Initiation3D Game Studio Initiation

Example of games programmed in 3Dgame StudioExample of games programmed in 3Dgame StudioMore at www.3dgamestudio.com

Documents

Electrical and Computer Engineering Dept