Methodology for Developing VR Contents

Virtual reality (VR) interfaces contain a richer variety and more complex types of objects, behaviors, interactions, and communications, Compared to conventional interfaces. Therefore, designers of VR interfaces face significant conceptual and methodological challenges in :

a) thinking comprehensively about the overall design of the VR interface.

 b) decomposing the design task into smaller, conceptually distinct, and easier tasks. 

c) communicating the structure of the design to software developers. 

To help designers to deal with these challenges, we propose a Virtual Reality Interface Design (VRID) Model and an associated VRID methodology. Virtual Reality (VR) is seen as a promising platform for the development of new applications in many domains such as medicine, entertainment, science, and business. Despite their potential advantages, however, we do not yet see widespread development and use of VR applications in practice. The lack of proliferation of VR applications can be attributed partly to the challenges of building VR applications. 

In particular, interfaces of VR applications are more complex and challenging to design compared to interfaces of conventional desktop based applications. VR interfaces exhibit distinctive visual, behavioral and interaction characteristics.

1. Visual characteristics. While conventional interfaces mainly use 2D graphical displays, VR interfaces use both 2D and 3D displays. A major goal of virtual environments is to provide users with realistic environments. In order to provide the sense of “being there,” VR interfaces heavily use 3D graphical displays. Design and implementation of 3D graphical displays are usually more difficult than 2D displays. Conventional interfaces typically contain only virtual, computer-generated objects. VR interfaces, on the other hand, may contain both virtual and physical objects that coexist and exchange information with each other, as in the case of augmented reality systems. The need to properly align virtual and physical objects constitutes an additional challenge in VR interface design 

2. Behavioral characteristics. In conventional interfaces, objects usually exhibit passive behaviors. In general, they have predetermined behaviors that are activated in response to user actions. Therefore, communication patterns among objects are usually deterministic. VR interfaces contain both real-world-like objects and magical objects that exhibit autonomous behaviors. Unlike passive objects, autonomous objects can change their own states. They can communicate with each other and affect each other's behaviors and communication patterns. Therefore, designing object behaviors is more challenging in VR interfaces.

3. Interaction characteristics. While conventional interfaces support mainly explicit style interactions, VR interfaces usually support both explicit and implicit style interactions. Implicit style interactions allow more natural and easier to use human-computer interactions by allowing arm, hand, head, or eye movement based interactions. However, these implicit style interactions are more complex to design compared to explicit style interactions.

 COMPONENTS OF A VIRTUAL REALITY SYSTEM

Before introducing the VRID model, it is important to clarify what we mean by a VR interface. we conceptualize a VR system in terms of three major components: application, interface, and dialog control inspired by the Seeheim user interface system architecture and the Model View Controller architecture. The application component is the VR application itself, which contains features, rules, and knowledge defining the logic of the application. The interface component is the front-end through which users and other external entities exchange information with and manipulate the system. The interface consists of data and objects. Data refers to inputs received from users whereas objects refer to entities in the interface that have well-defined roles and identities. Dialog control enables communication between the application and the interface. Due to conceptual separation, internal details of application and interface components are transparent to each other. This feature allows designers to work on the two components independently. We propose the VRID model and methodology only for the design of the interface component. 

 THE VRID MODEL 

Building on our review and synthesis of the previous work on VR interface design, we identify object graphics, object behaviors, object interactions and object communications as the key constructs that designers should think about in designing VR interfaces. Therefore, we organize the VRID model around a multi-component object architecture that is depicted. Graphics, behavior, interaction, and communicator components are included to conceptually distinguish and address the distinctive characteristics of VR interfaces. The mediator component is included to coordinate communications among the other four components of an object. These five components serve as the key constructs of our design model. 

The graphics component is for specifying graphical representations of interface objects. It covers the specification of all graphical models that are needed for computer-generated appearance and animations of the objects. We include the graphics component in the model in order to address the distinctive visual characteristics of VR interfaces. VR interface objects exhibit more complex behaviors and these behaviors need to be represented by more complex visual displays, it is important to associate object behaviors with object graphics at a high level of abstraction. In general, responsibility for the design of visual aspects of VR interfaces lies with graphics designers rather than VR interface designers. That is why we treat the graphics component as a black box and focus only on its outcomes, i.e., graphical models. 

The guidance to VR interface designers in specifying graphical models associated with interface objects and their behaviors. By doing so, we seek to facilitate communications between graphics designers and VR interface designers so that graphical representations and animations generated by graphics designers are compatible with behaviors specified by interface designers.The behavior component is for specifying various types of object behaviors. In order to help designers to understand and simplify complex object behaviors, we categorize object behaviors into two groups: physical behaviors and magical behaviors. Physical behavior refers to those changes in an object’s state that are observable in the real world. Magical behavior refers to those changes in an object’s state, which are rarely seen, or not seen at all in the real world.

Breaking down complex behaviors into simple physical and magical behaviors serve two purposes. First, it allows designers to generate a library of behaviors, which can be reused in creating new behaviors. Second, physical and magical distinction enables designers to assess the level of detail required in communicating design specifications to software developers unambiguously. Physical behaviors are relatively easy to describe and communicate. Since they have counterparts in the real world, software developers can easily relate to physical behaviors. Hence, interface designers may not need to describe all details of physical behaviors. Magical behaviors, on the other hand, are either rarely seen or not seen at all in the real world. Software developers may have difficulty in visualizing the magical behaviors. Interface designers may need to specify magical behaviors in more detail to avoid any misunderstandings in the later stages of development. Objects may exhibit composite behaviors that consist of a series of simple physical and magical behaviors. 

For example, running behavior of an athlete can be considered as a composite behavior consisting of simple physical behaviors such as leg and arm movements. By conceptually distinguishing between “simple” and "composite behaviors," These help designers to decompose complex behaviors into smaller, conceptually distinct parts and to increase the reusability of the resulting software code. Designers can combine simple behaviors in different ways and sequences to generate new composite behaviors. Breaking down a complex behavior into simpler behaviors also increases clarity of communication between designers and software developers since it is easier to visualize a series of simpler behaviors. We devote specific attention to the design of object behaviors because defining object behaviors has typically been a challenge in VR. Most virtual environments remain visually rich but behaviorally impoverished.Behavioral characteristics of VR interfaces do not provide high-level guidance for decomposing complex behaviors into simpler behaviors. By proposing physical-magical and simple-composite categories, we aim to help designers to decompose complex behaviors into simpler, easier to design components, which can also be reused in creating new behaviors. 

The interaction component is used to specify where inputs of the VR system come from and how they change object behaviors. The interaction component receives the input, interprets its meaning, decides on the implication of the input for object behavior, and communicates with behavioral components to make the desired change in the object behavior. VR interfaces need to support implicit style interactions, which require monitoring and interpretation of inputs such as hand, arm, head and eye movements. Each of these interaction types presents a particular design challenge. which usually merge the design of interactions and behaviors.The conceptual distinction between interactions and their implications for object behaviors. This distinction allows designers to focus on the challenges of interactions in the interaction component, and on the challenges of behaviors in the behavior component. It also increases reusability of resulting interactions and behaviors since interactions and behaviors are de-coupled from each other.The mediator component is for specifying control and coordination mechanisms for communications among other components of the object. The goals are to avoid conflicts in object behaviors and to enable loose coupling among components. To achieve these goals, we propose the mediator component by adapting the concept of “mediator design pattern” suggested by Gamma and colleagues.

 The mediator controls and coordinates all communications within the object. When a component needs to communicate with another component, it sends its message to the mediator rather than sending it directly to the destination. This component enables designers to identify, in advance, which communication requests might lead to conflicts in object behaviors, and to specify how the requests can be managed to avoid the conflicts. Since a component only needs to know about itself and the mediator rather than having to know about all components with which it might communicate, the mediator component also ensures loose coupling between components. 

The communication component is for external communications of the object with other objects, data elements, or with the application component. In this component, designers need to specify sources of communication inflows into the object, destinations of communications outflows from the object, and the message passing mechanisms between them such as the synchronous, asynchronous, balking, or timeout mechanisms discussed by Booch. The object behaviors discuss message-passing mechanisms among objects with low-level specifications of behaviors. The difference in our approach is that we start analyzing the communication needs of objects at a higher level of abstraction and that we make a distinction between internal and external communications of objects. By using two separate components for specification of internal and external communications mechanisms of objects, we help designers to decompose the complexity associated with the design of communications into smaller, conceptually distinct components, which are easier to analyze, design, code, and maintain. 

The VRID model synthesizes VR interface design and proposes a comprehensive set of modeling structures in the form of a multi-component object architecture, which helps designers to see clearly which issues and decisions are involved in VR interface design.

Information from: Vildan Tanriverdi and Robert J.K. Jacob