A FRAMEWORK FOR H-ANIM SUPPORT IN NVES

Ch. Bouras

1,2

Research Academic Computer Technology Institute (CTI), Greece

Computer Engineering and Informatics Department (CEID), University of Patras, Greece

K. Chatziprimou

Computer Engineering and Informatics Departmet (CEID), University of Patras, Greece

V. Triglianos

3,4

Research Academic Computer Technology Institute (CTI), Greece and

Computer Engineering and Informatics Departmet (CEID) University of Patras, Greece

Th. Tsiatsos

5,6

Department of Informatics, Aristotle University of Thessaloniki, Greece

Research Academic Computer Technology Institute (CTI), Greece

Keywords: Virtual reality, H-Anim, Humanoid Animation, Anim

ation, Networked Virtual Environments, Multimedia

systems, Architecture, and Applications.

Abstract: Many applications of Networked Virtual Environment presuppose the users’ representation by humanoid

avatars that are able to perform animations such as gestures and mimics. Example applications are computer

supported collaborative work or e-learning applications. Furthermore, there is a need for a flexible and easy

way to integrate humanoid standardized avatars in many different NVE platforms. Thus, the main aim of

this paper is to introduce a procedure of adding animations to an avatar that is complying with H-Anim

standard and to present a standardized way to integrate avatars among various NVEs. More specifically this

paper presents a framework for adding/loading custom avatars to an NVE and applying to them a set of

predefined animations, using H-Anim standard.

1 INTRODUCTION

Currently, a large number of Networked Virtual

Environments (NVEs) have made their way to the

public. Users are represented in NVEs by entities

called avatars. Using virtual humans to represent

participants promotes realism in NVEs (Capin et. al,

1997). Moreover, users tend to develop a

psychological bond with their avatar/s. One of the

main tasks in a NVE is the integration of humanoid

avatars and humanoid animations on top of them.

This could be useful in order for the users to transfer

their avatars from an NVE to another. In many

Networked Virtual Environments, such as Massively

Multi-User Online Role-Playing Games, users are

given a large degree of control over the appearance

of their avatars (Yee, 2006). Usually the users

exploit this functionality to customize their avatars

in order to reflect their real or virtual personality.

The creation and integration of virtual humans

that are compatible in many different NVE

platforms is a challenging task for the following

reasons: (a) It requires the creation of a humanoid

avatar based on a standardized way; (b) The creation

of humanoid animation is a complex task which

usually requires particular skills and training

(Buttussi et al., 2006); and (c) there is no

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Bouras C., Chatziprimou K., Triglianos V. and Tsiatsos T. (2009).

A FRAMEWORK FOR H-ANIM SUPPORT IN NVES .

In Proceedings of the Fourth Inter national Conference on Computer Graphics Theory and Applications, pages 286-291

 SciTePress

standardised way to integrate and share humanoid

avatars in a networked virtual environment.

The first challenge has been resolved with the H-

Anim standard (Humanoid Animation Working

Group, 2004), now included in X3D, which

describes humanoids as an hierarchically organized

set of nodes. Furthermore, Ieronutti and Chittaro

(2005) proposed Virtual Human Architecture

(VHA), which is an architecture that integrates the

kinematic, physical and behavioral aspects to control

H-Anim virtual humans. This solution is fully

compatible with Web standards and it allows the

developer to easily augment X3D/VRML worlds

with interactive H-Anim virtual humans whose

behavior is based on the Sense-Decide-Act

paradigm (represented through HSMs).

Concerning the animation (which is the second

challenge) there are many tools (free of charge or

commercial) which simplify this process by visual

authoring tools. Buttussi et al., (2006), present such

a tool called H-Animator as well as an overview of

other visual authoring tools. However, the main

problem is the third challenge because there is no

standardized way to integrate and share humanoid

avatars in a networked virtual environment. Miller

(2000) achieved to provide an interface to aggregate

and control articulated humans in a networked

virtual environment by addressing the following

areas:

• The creation of an articulated joint structure of

virtual human avatars and a limited motion

library in order to model realistic movement.

More specifically Miller (2000) achieved rapid

content creation of human entities through the

development of a native tag set for the

Humanoid Animation (H-Anim) 1.1

Specification in Extensible 3D (X3D).

• The development and implementation of a set of

rule-based physical and logical behaviors for

groups of humans in order to execute basic

tactical formations and activities.

• The aggregation of human entities into a group

or mounting of other human entities (such as

vehicles) and then separation back to individual

entity control. Otherwise, the high-precision

relative motion needed for group activities is

not possible across network delays or in geo-

referenced locations.

Even though Miller’s work is based on standards it

does not solve the problem of dynamic avatar

creation and change. Based on the above, it is

obvious that there is an need for a flexible and easy

way to integrate humanoid standardized avatars in

many different NVE platforms. Rapid application

development process could help on this direction by

utilizing reusable frameworks and API’s. This work

deals with two important challenges in the field of

NVEs. The first is the procedure of adding

animations to an avatar that is complying with a

standard, in our case H-Anim. The second is to

introduce a standardized way to integrate avatars

among various NVEs. Our contribution focuses on

providing a framework that allows a user to upload

an avatar to an NVE, to automatically add

predefined animations to it and integrate it to the

environment. All these steps could happen at

execution time. More specifically, in this paper we

present a framework that allows any X3D compliant

platform to import an H-Anim compliant avatar, to

add a set of custom animations to it and finally, to

add the avatar to the virtual environment.

This work is structured as follows. The next

section is an overview of an NVE Platform called

EVE that is the platform we used to integrate and

test our framework. Afterwards, the architecture of

the proposed solution is presented. The fourth

section describes the process of integrating the

framework to an NVE. The fifth chapter illustrates

practical examples concerning the practical

exploitation the proposed framework. The final

section presents the concluding remarks and our

vision for the next steps.

2 EVE OVERVIEW

Even though the proposed H-Anim integration

framework aimed to support any NVE platform

based on X3D standard, we are presenting it through

its integration in EVE (http://ouranos.ceid.upatras.gr/vr)

networked virtual environments platform (Bouras et

al, 2006).

Thus, it is essential to present the main

characteristics of this platform. EVE is based on

open technologies (i.e. Java and X3D).

It features a client – multi-server architecture

with a modular structure that allows new

functionality to be added with minimal effort.

Initially, it provides a full set of functionalities for e-

learning applications and services, such as avatar

representation, avatar gestures, content sharing,

brainstorming, chatting etc.

Furthermore, the current version of the platform

supports collaborative design applications. Currently,

the architecture of the platform consists of five

servers as shown in Figure 1.

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287

Figure 1: EVE Architecture.

The “Connection Server” coordinates the

operation of the other servers. The “VRML-X3D

Server” is responsible for sending the 3D content to

the clients as well as for managing the virtual worlds

and the events that occur in them. The “Chat Server”

supports the text chat communication among the

participants of the virtual environments.

The “SIP Spatial Audio Conferencing Server” is

used in order to manage audio streams from the

clients and to support spatial audio conferencing.

Finally the “2D Application Server” is handling the

generic (i.e. non - X3D) events.

On the client side, the interface of the platform is

rendered by a Java applet that incorporates an X3D

browser (based on Xj3D API). The following

section presents the architecture of the new H-Anim

component integrated in EVE platform and

describes its operation.

3 H-ANIM COMPONENT

ARCHITECTURE

In this section the architecture behind the framework

for H-Anim support in NVEs is presented.

The "H-Anim 200X" standard has been chosen

for the representation of humanoid models in EVE

platform. Originally created to enable the design and

exchange of humanoids in virtual online

environments, the Η-anim standard offers a suitable

data structure for the real time animation. The main

features of H-anim standard are the following:

• Support of VRML, XML and X3D data

formats.

• Support of five (5) types of nodes: Humanoid,

Joint, Segment, Site and Displacer nodes.

• Different levels of complexity are suggested.

These suggestions are called "Levels Of

Articulation" of the skeleton (LOA). There are

three of them (excluding the trivial, zero LOA),

varying in number of joints and sites needed.

• Objects that are not part of the anatomy can still

be specified within the H-Anim humanoid data

structure.

• "Skinning" the avatar is made possible by a dual

specification of the body geometry, which is

divided into the skeletal and the skinned part.

Moreover, the anatomy is specified through a tree-

like hierarchical structure of H-Anim specific nodes,

which is referred to as the skeletal body geometry

specification.

Figure 2: Architecture Components.

As long as a client (i.e. a user) wishes to connect

to the NVE, using her/his own avatar and utilize the

supplied animations, her/his humanoid has to be H-

Anim compliant. The overview of the architecture of

the proposed H-Anim component is presented

in Figure 2

The following paragraphs describe:

• the mechanism for inserting an H-Anim avatar

in an NVE platform along with its animations.

• the main parts of the H-Anim component (i.e.

the parser and the user interface).

3.1 Mechanism

The operation of H-Anim component presupposes

the availability of a VRML/X3D file that contains

the avatar as well as a set of VRML /X3D

animations.

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Figure 3: Flowchart of the import process.

Based on these necessary inputs, the operation of the

H-Anim component is based on the following steps

(Figure 3):

• File submission and opening: Reading of the

VRML/X3D file that contains the avatar.

• Validation of X3D/VRML compliance:

Validation of the above file. If it’s a valid

X3D/VRML file, visualize it on a Xj3D

Visualization Panel. If not a response

describing the problem is displayed and the user

can try again by restarting this process.

• File insertion: Using the Xj3D Visualization

Panel the user can import the already validated

(against VRML/X3D) avatar file in order to

perceive its Level Of Articulation (LOA). If

LOA is equal or greater than 0 then we move to

the next step. If this is not the case then a

message describing the problem is displayed.

The user can try to upload another file.

• Animation readiness validation: Check the file

to find out if the joints that are required by the

list of animations that we want to append, are

present. If they are, then the animations are

added to the avatar. If not then we simply

import dynamically the avatar to the NVE. In

the latter case a message informs the user that

although his/her avatar was imported to the

platform, the animations he chose were not

added to the avatar due to joints

incompatibility.

• Integration of animations: Finally, when all of

the above controls are completed, the

Animation Adder can be utilized. Choosing the

option “Add Animation” from the main menu, a

dialog frame pops up, and the user can select,

among a list of animations, the animation he

wishes to append to his avatar.

3.2 The Main Parts of the H-Anim

Component

The framework’s architecture mechanism consists of

five main parts: the X3D/VRML Parser, the Xj3D

Visualizer, the H-Anim Validator, H-Anim Joints

Parser and finally the Animation Adder. The

following paragraphs describe each one of the above

respectively.

The X3D/VRML Parser, based on Xj3D API,

which provides both syntax and semantic level

checking, is given a URL that represents the location

of a X3D/VRML file, making it transparently useful

as either part of a web browser or standalone client.

As the parser carries out the VRML/X3D grammar,

a set of VRML/X3D nodes is generated.

Once the parsing of the client’s file is correctly

accomplished, the content is displayed in the Xj3D

Visualizer. The interface that hosts the Xj3D

Visualizer, provides an option menu wherein the

user can browse a file in his computer system, and

thereafter submit it to H-Anim Validator. As long as

the selected file is validated as H-Anim compliant,

the client is enabled to interact with a dialog menu,

choose the desired animation and therefore apply it

to his own avatar.

Figure 4: User Interface main menu.

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In particular, the H-Anim Joints Parser takes as

input the location of the user’s avatar file, and

examines if there exists an hierarchical structure of

H-Anim specific joints. The H-Anim Joints Parser

searches for the joints required by the selected

animation. Such a check is crucial in order for the

desired animation to be compatible with the offered

3D avatar. As has been already mentioned before,

the skeleton of the avatar consists of a sequence of

mutually alternating joints and segments (bones). By

that way, a graph is formed, where joints represent

vertices and segment stand for edges. The root of the

graph is referred to as the basis. The leaf of the

graph is called the end effector. The illusion of the

movement of the humanoid is reached by rotating

the segments around the joints. Consequently if

specific joint nodes are missing, no animation can

occur. As a result only if the user’s humanoid is H-

Anim compliant, containing the necessary joint’s

sequence, the existing animation can be attached to

her /his file. Responsible for the latter is the

Animation Adder, which appends the animation

code to the avatar’s file, under the correct context.

Finally, the user may clear the history of his actions.

4 FRAMEWORK INTEGRATION

There are three major steps in order to integrate this

work to an NVE, as were done in EVE’s case. The

first deals with the Graphic User Interface (GUI) of

the Framework. The second deals with the input and

output of the framework. In the next two paragraphs

we will address this two issues respectively.

The entire user interface of the framework is

embedded in a JFrame class instance. This makes it

very easy to integrate it to both desktop and

WebTop applications that are developed in Java.

The process of adding the framework GUI to EVE

was very simple: We just added the JPanel object to

the specific portion of the JApplet object that forms

EVE’s GUI.

The framework needs to have access to the

X3D/VRML code of the set of animations that an

NVE supports. The path to these animations can be

appended to a configuration file that the framework

reads during initialization. Finally the output of this

framework, that is X3D/VRML files that describe an

avatar along with the set of animations that were

added to it, can be stored to a specific location

(described in the configuration file). Once the output

is produced, the framework can be configured to call

one or more NVE specific functions that adds/add

the X3D/VRML code of the avatar to the virtual

world. In EVE a function that adds X3D/VRML

content to the world was invoked as soon as the

framework produce the avatars file.

5 EXAMPLE APPLICATIONS

Example applications for this framework could be

distance learning or collaborative work applications.

Bailenson and Beall (2006) said that given the

advent of collaborative virtual reality technology, as

well as the surging popularity of interacting with

digital representations via collaborative desktop

technology, researchers have begun to

systematically explore this phenomenon of

Transformed Social Interaction (TSI). TSI

(Bailenson et. al 2004) involves novel techniques

that permit changing the nature of social interaction

by providing interactants with methods to enhance

or degrade interpersonal communication. Our

proposed framework could be used in order to

support the implementation of TSI by attaching in

real time humanoid animations in users’ avatars.

Furthermore, we can exploit the proposed

framework for supporting role changing in

collaborative e-learning scenarios that are conducted

in a NVE. Our framework can offer the dynamic

change of avatars according to the users’

roles.

Figure 5A, shows an avatar in which we have

added various animations hat have been created by

the proposed process and is able to walk (Figure 5B,

C and D), salute (Figure 5E) and raise a hand

(Figure 5F).

Figure 5: Example avatar.

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6 CONCLUSIONS

FUTURE WORK

This paper presented a framework that (a) allows a

user to import custom H-Anim avatars to an NVE

and (b) adds the animations that are supported by

the NVE to an H-Anim Avatar. This framework

enables NVE’s developers to quickly add H-Anim

support to their applications. In addition, users can

benefit from this framework, in the sense that they

are able to import their favourite avatars in every

NVE they like.

Our next steps will focus on designing and

implementing a VRML/X3D visual editor that will

allow the user to modify his/her avatar at execution

time and before importing it to an NVE. We also

focus on releasing a Public API for this work.

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