VIRTUAL REALITY (VR) INTRODUCTION AND BASIC APPLICATIONS الواقع الافتراضي : مقدمة وتطبيقات Dr. Naji Shukri Alzaza Assist. Prof. of Mobile technology Dean of Community Service and Continuing Education University of Palestine, Alzahra City, Gaza, Palestine

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OBJECTIVES Dr. Naji Shukri Alzaza 3 Students should be able to: 1. Understand the concept of virtual environment. 2. List and describe all the components of a virtual environment which include: i. Virtual Objects ii. Virtual Lights iii. Animation iv. Physical Simulation v. Level of detail vi. Collision Detection

Virtual Environment (VE) Dr. Naji Shukri Alzaza 4  VE is a computer generated world with which the user can interact and interaction can vary from looking around to interactively modifying the world.  It is a high-end user-computer interface that involve real time simulation and interaction through multiple sensory channels which include visual, auditory, tactile, smell and taste.  VE simulates real or imaginary system that enables a user to perform operations on the simulated system and shows the effects in real time.  VE can take many forms, such as realistic representation of physical environment such as interior of building, kitchen, cars and etc.

Virtual Environment (VE) Dr. Naji Shukri Alzaza 5  VE might not have any physical basis at all, example: a 3D database of geographical, hierarchical network of a company as well as multi-dimensional data set for stock transaction.  VE can be used to evaluate physical simulation such as simulating molecules within electric fields, dynamic behaviors of atomic particles and accidents scenes.  In the most successful virtual environments, users feel that they are truly present in the simulated world and that their experience in the virtual world matches what they would experience in the environment being simulated.  This sensation is referred to as engagement, immersion, or presence.

Virtual Environment (VE) Dr. Naji Shukri Alzaza 6  VE consists of a collection of virtual objects and light sources which are manipulated by animation and physical simulation sources.  Collision detection algorithms are also incorporated into the VE to monitor collisions between specified objects.

Virtual Environment (VE) 7 The Inputs, Processes And Outputs In A Generic VR System (Vince, J. (1995). Virtual reality systems : ACM Press/Addison-Wesley Publishing Co. New York, NY, USA.) VE

Virtual Objects Dr. Naji Shukri Alzaza 8  To represent a participant or physical object in a VE; the typically visual representation may take any form.  Virtual objects are objects that are used to build Virtual environments.  Virtual objects posses 3D geometries, color and texture, dynamic characteristics, physical constraints and acoustic properties.  Virtual objects can be categorized as static and dynamic objects.  In a virtual architectural environment, example of static objects are floors, walls, ceilings, stairs etc., for dynamic objects are doors, windows, drawers etc.

Virtual Objects Dr. Naji Shukri Alzaza 9  Some dynamic objects may be defined without any constraints upon their spatial behavior while others may be physically constrained to move within prescribed limits, example: drawers and doors.  Virtual objects can be constrained to limit their translational and rotational properties.  3D graphics is a computer-intensive application and when it is conducted in real-time (VR), it imposes severe constraints upon the computer system.

Virtual Objects Dr. Naji Shukri Alzaza 10  Attempt has to be made to keep the system update rate running as high as possible.  The complexity of the VE database plays a significant factor in determining this speed.  Therefore, it is important to minimize the polygon count without affecting the VE system.

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Virtual Lights Dr. Naji Shukri Alzaza 12  Lighting is important in illuminating the VE so that users are able to see the virtual objects properly.  Lighting can also play an important part in enhancing the mood and atmosphere of the VE experience.  Good lighting reduces the perceptual differences between a real and a virtual object, and can allow the audience to recognize the material of the virtual object better without requiring touch.

Virtual Lights Dr. Naji Shukri Alzaza 13  Shadows can give the audience important depth cues for placing virtual objects in the scene.  When extra computing power is available, it is possible to implement a complete illumination model incorporating several light sources.  Moreover, the user can even explore the VE with a moveable light source to mimic the action of a handheld torch.

Virtual Lights Dr. Naji Shukri Alzaza 14

FRONT (original) TOP (ints 5) FILL Daylight- Blue Dr. Naji Shukri Alzaza 15

Animation Dr. Naji Shukri Alzaza 16  The most exciting contribution offered by computers is the ability to create and animate 3D virtual objects.  Animation is “a process of animating objects that appear in a three-dimensional space where they can be rotated and moved like real objects”.  In order to animate virtual objects in a VE, the user can only perform tasks that are supported by the software.  Animation is key to the interaction capabilities of VEs.  Animation does not imply that objects in the scene are moving; it could be that the viewpoint of the user is changing, as in an architectural walkthrough application.  As such, animation is critical to Virtual Reality; without it, we would simply be looking at three-dimensional photographs.

Animation Dr. Naji Shukri Alzaza 17

Physical Simulation Dr. Naji Shukri Alzaza 18  Simulation is “a representation of the operation or features of one process or system through the use of another”.  Physical simulation refers to simulation in which physical objects are substituted for the real thing.  These physical objects are often chosen because they are smaller or cheaper than the actual object or system.  Physical simulation allows simulated objects to behave in a physically realistic fashion.  This means that objects in the simulated world can be configured to behave just as real objects do.

Physical Simulation Dr. Naji Shukri Alzaza 19  Physical simulation is typically necessary when dealing with physically realistic jointed bodies, such as a simulated robot or simulated animal.  Physical simulation attempts to replicate real-world processes on a laboratory scale in a way that the resultant data can be used to solve real-world problems.  Example of usage: linked structures, human motion and natural phenomena.

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Level of detail (LOD) Dr. Naji Shukri Alzaza 21  Level of detail involves storing within the database different levels of detail for specific virtual objects.  There are numerous schemas to implementing LOD, using selection criteria based upon an object’s  Distance  Size  Velocity  Eccentricity (irregularity, oddness)

Level of detail Dr. Naji Shukri Alzaza 22  Distance  An object’s level of detail is based upon the viewpoint.  Size  An object’s level of detail is based upon a measure of its pixel size, or area, on the display device.

Level of detail Dr. Naji Shukri Alzaza 23  Velocity  an object’s level of detail is based upon velocity relative to the user i.e. its velocity across the display device or the user’s retina.  Eccentricity  An object’s level of detail is based upon the degree to which it exists in the periphery of either the display device or the user’s field of view.

Level of detail Dr. Naji Shukri Alzaza 24  LOD enables the real-time system to automatically selects the model description that matches the current view and mode of operation.  LOD is an important tool for maintaining interactivity.  The problem: Geometric datasets can be too complex to render at interactive rates.

Level of detail Dr. Naji Shukri Alzaza 25  Solution: Simplify the polygonal geometry of small or distant objects.  LOD is also known as:  polygonal simplification  geometric simplification  mesh reduction  decimation  multiresolution modeling

Level of detail Dr. Naji Shukri Alzaza 26  Create levels of detail (LODs) of objects 69,451 polys 2,502 polys251 polys76 polys

Level of detail Dr. Naji Shukri Alzaza 27 Distant objects use coarser LODs

Level of detail Dr. Naji Shukri Alzaza 28

Collision Detection Dr. Naji Shukri Alzaza 29  In VE we need to detect collisions happening between two (or more) virtual objects in order to avoid penetration, and also to perform the necessary responses on time.  This is done through the use of bounding spheres or bounding boxes.  The size of sphere or box completely constrains the virtual objects with which it is associated.  For example in a VE, when the user walks into a wall, then the user will either stop or will continue sliding along the wall.

Collision Detection Dr. Naji Shukri Alzaza 30 Sphere Bounding BoxBounding Boxes

Collision Detection Dr. Naji Shukri Alzaza 31

Collision Detection Dr. Naji Shukri Alzaza 32  The range of applications that require collision detection is extensive.  Vehicle simulators are one case where the users manipulate a steering device and attempt to avoid obstacles in their path.  In molecular modeling, simulation allows interactive testing of new drugs to examine how molecules interact and collide with each other.  Training and education systems that realistically model the movement of objects within the geometric constraints of their layout, allow designers to experiment interactively with different strategies example; to assemble or disassemble equipment, to perform a virtual surgery, or to test different paths that a robot could take.

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