Full HTML for

Basic foilset VRML and Use of Databases as backend and Application to GIS

Given by Krzysztof Walczak at ARL Database Tutorial on February 98. Foils prepared 7 October 97
Outside Index Summary of Material

Open Inventor
VRML language
VRML Browsers
Illustra Database System
Why database support for VRML ?
File based terrain rendering in VRML
Terrain rendering with Illustra database support
Objects - storing rich semantic information
Multiversion representation
Examples of VRML for Terrain Rendering

Table of Contents for full HTML of VRML and Use of Databases as backend and Application to GIS

 Denote Foils where Image Critical
Denote Foils where HTML is sufficient
1 VRML and Database Support
2 Topics in VRML/Illustra Tutorial
3 Open Inventor and VRML -- Introduction
4 Open Inventor -- Overview
5 Open Inventor -- Nodes
6 Open Inventor -- Database Structure
7 Open Inventor -- Typical Applications
8 VRML - Virtual Reality Modeling Language -- Overview
9 VRML Goals
10 VRML -- Specification
11 VRML - Language characteristics
12 Example I - Shapes
13 Example II - Properties
14 Example III - Group Nodes
15 Example IV - Textures
16 VRML - Nodes I
17 VRML - Nodes II
18 VRML - Nodes III -- Properties nodes
19 VRML - Nodes IV
20 VRML - Example
21 VRML - Tools
22 VRML - Browsers
23 VRML - Browsers II
24 VRML Browsers - Examples I -- WebSpace
25 VRML Browsers - Examples II -- SDSC WebView
26 VRML Browsers - Examples III -- VRWeb
27 VRML Browsers - Examples IV -- WebFX
28 Illustra Database System - Server
29 Illustra - Evolution in DBMS
30 Illustra Database System
Object-Relational DBMS
31 Illustra Database System - DataBlades
32 Illustra Database System
DataBlades (cont.)
33 Illustra - System Architecture
34 Illustra Database System --
2D Spatial DataBlade
35 Illustra Database System --
3D Spatial DataBlade
36 Illustra Database System
Access to the Data
37 Database Support for VRML
38 Why Database Support for VRML ?
39 Standard VRML Storage
Characteristics
40 Standard VRML Storage
Disadvantages
41 Geometrical vs. Semantical Model
42 System Architecture
43 VRML Synthesis
44 Terrain Data
45 Synthesis of Terrain Description
46 Creation of VRML files
47 VRML modeling
48 LOD - Level-Of-Detail
49 Level-Of-Detail - Example
50 Colors
51 Data Storage and Indexing
52 Reducing Number of Polygons
53 Multi Resolution Terrain Model - I
54 Multi Resolution Terrain Model- II
55 Modeling of Objects - Object Data
56 Modeling of Objects - Types
57 Definition of Objects - Example
58 Database Schema
59 Multiversion Approach
60 Multiversion Approach
61 Terrain rendering in VRML - Example I
62 Terrain rendering in VRML - Example II

Outside Index Summary of Material

HTML version of Basic Foils prepared 7 October 97

Foil 1 VRML and Database Support

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Gang Cheng, Geoffrey C. Fox, Nancy McCracken, Marek Podgorny, Chao-Wei Ou, Krzysztof Walczak
Northeast Parallel Architectures Center
Syracuse University
HTML version of Basic Foils prepared 7 October 97

Foil 2 Topics in VRML/Illustra Tutorial

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Open Inventor
VRML language
VRML Browsers
Illustra Database System
Why database support for VRML ?
File based terrain rendering in VRML
Terrain rendering with Illustra database support
Objects - storing rich semantic information
Multiversion representation
Examples of VRML for Terrain Rendering
HTML version of Basic Foils prepared 7 October 97

Foil 3 Open Inventor and VRML -- Introduction

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Open Inventor is an object-oriented 3D toolkit to create interactive 3D graphics applications.
It is also a high-level object-oriented model for specifying, processing, rendering, archiving and managing complex, hierarchical structures such as encountered in 3D design.
VRML is intended to be a language for describing multi-participant interactive simulations - virtual worlds networked via global Internet and hyperlinked within the World Wide Web.
The first, existing VRML specification is based on the Open Inventor ASCII file format and is a minimal operational subset of Open Inventor extensive class library.
HTML version of Basic Foils prepared 7 October 97

Foil 4 Open Inventor -- Overview

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The library was originally developed by Silicon Graphics, Inc. as the IRIS Inventor library but is now licensed to a number of implementors and is appearing for a range of platforms including Sun, IBM, HP, Windows, Mac and HP.
Open Inventor characteristics:
  • It's built on top of OpenGL.
  • It defines a standard file format for 3D data interchange.
  • It introduces a simple event model for 3D interaction.
  • It provides animation objects called 'Engines'.
  • It is window system and platform independent.
  • It supports PostScript printing.
HTML version of Basic Foils prepared 7 October 97

Foil 5 Open Inventor -- Nodes

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
The node is the basic building block used to create three- dimensional scenes in Open Inventor. Each node holds a piece of information, such as a surface material, shape description, geometric information, light or camera.
The Open Inventor nodes can be grouped as follows:
  • Shape nodes - representing 3D geometric objects
  • Property node - representing appearance and other qualitative characteristics of the scene such as material, lighting model, textures, or environment
  • Group nodes - containers collecting nodes into groups
  • Engines - can be attached to other nodes and drive animation or impose constraints
  • Sensors - detect changes in the scene database and invoke suitable notification/callback functions
HTML version of Basic Foils prepared 7 October 97

Foil 6 Open Inventor -- Database Structure

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Open Inventor maintains a database of objects.
The database contains information representing one or more 3D scenes.
The database consists of scene graphs.
A scene graph is an ordered collection of nodes.
A number of actions can be applied to a scene graph.
HTML version of Basic Foils prepared 7 October 97

Foil 7 Open Inventor -- Typical Applications

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Geophysical Visualization,
Commercial Database Visualization,
CAD,
Desktop Publishing,
Modeling and Industrial Design,
Computer-based Training,
Collaborative Work,
Animation,
Visual Simulation,
Interactive 3D games,
Scientific Data,
Visualization Presentations,
Virtual Reality
HTML version of Basic Foils prepared 7 October 97

Foil 8 VRML - Virtual Reality Modeling Language -- Overview

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Mission Statement:
VRML (Virtual Reality Modeling Language) is an interpreted language for describing multi-participant interactive simulations - virtual worlds networked via global Internet and hyperlinked within the World Wide Web.
History:
VRML concept was proposed by Tim Berners-Lee and David Ragget in spring '94 during the first WWW conference in Geneva. After the conference the VRML forum was created by Mark Pesce to discuss the development of a specification. In May '95 the first version of specification was available.
Current status:
  • VRML is still under development.
  • The currently available specification describes version 1.0.
  • Next version - 1.1 only specified small changes and was superceded by version 2.0.
  • Version 2.0 was released in May '96 but there is competition from activeVRML (Microsoft) and Java3D (SGI) which has support for richer subset of Inventor.
HTML version of Basic Foils prepared 7 October 97

Foil 9 VRML Goals

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
The current form of VRML has been strongly influenced by the following requirements:
  • - Platform independence
  • - Extensibility
  • - Ability to work over low-bandwidth
  • connections -- but here it didn't succeed as format is clearly inefficient and this is clearly handicapping acceptance
HTML version of Basic Foils prepared 7 October 97

Foil 10 VRML -- Specification

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
The current version of VRML specification - 1.0 is a minimal starting point for a much larger concept.
The specification is based on Open Inventor ASCII file format.
VRML 1.0 is a subset of Open Inventor with some additions that allow linking the objects with another VRML or HTML sites on the Web. The linking concept is similar to HREF in HTML.
VRML 1.0 provides only mechanisms for synthetic 3D "clickable worlds" and does not specify yet any constructs for object animation, behavior and interaction. These issues are currently under intense discussion by the VRML forum (and spinoffs such as VAG) and is included in version 2.0 of the language.
HTML version of Basic Foils prepared 7 October 97

Foil 11 VRML - Language characteristics

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Basics:
  • VRML defines a set of objects that can describe 3D graphics - nodes.
  • Nodes are arranged in hierarchical structures - scene graphs
  • Scene graphs define the ordering for the nodes - the state of the scene graph depends on the earlier and affects later nodes.
  • Separators can limit the effects allowing parts of the scene to be isolated from other parts.
Nodes are characterized by the following information:
  • Kind of object: cube, sphere, texture map, transformation, etc.
  • The parameters that describe the object,
  • The optional name of the object,
  • For some types of nodes - group nodes - the child nodes can be specified
HTML version of Basic Foils prepared 7 October 97

Foil 12 Example I - Shapes

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Shape nodes (Cube, Sphere) define the geometry of the objects in the scene.
HTML version of Basic Foils prepared 7 October 97

Foil 13 Example II - Properties

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The Material node defines the current surface material properties for all subsequent shapes.
HTML version of Basic Foils prepared 7 October 97

Foil 14 Example III - Group Nodes

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Separator node isolates its children from the rest of the scene graph.
HTML version of Basic Foils prepared 7 October 97

Foil 15 Example IV - Textures

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Texture node defines the texture map used to subsequent shapes.
HTML version of Basic Foils prepared 7 October 97

Foil 16 VRML - Nodes I

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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VRML nodes can be classified into three categories:
  • shape nodes - define the geometry in the scene,
  • property nodes - define the way shape nodes are rendered,
  • group nodes - gather other nodes into collections treated as single objects.
HTML version of Basic Foils prepared 7 October 97

Foil 17 VRML - Nodes II

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Shape nodes
  • AsciiText a string of text characters
  • Cone a simple cone along y-axis
  • Cube a cuboid aligned with coordinate axes
  • Cylinder a cylinder along y-axis
  • IndexedFaceSet a polygonal shape
  • IndexedLineSet a polyline shape
  • PointSet a set of points in 3D space
  • Sphere a simple sphere
HTML version of Basic Foils prepared 7 October 97

Foil 18 VRML - Nodes III -- Properties nodes

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Coordinate3 a set of 3D coordinates e.g. for IndexedFaceSet
FontStyle font style for AsciiText
Info information node
LOD - Level-Of-Detail switches between various object representations
Material surface material properties
MaterialBinding specifies how materials are bound to shapes
Normal a set of 3D surface normals, e.g. for IndexedFaceSet
NormalBinding specifies how normals are bound to shapes
Texture2 texture map and parameters for that map
Texture2Transform 2D transformation applied to texture coordinates
TextureCoordinate2 a set of 2D coordinates used by textures
ShapeHints topology hints for surface rendering
MatrixTransform a geometric 3D transformation matrix
Rotation 3D rotation (axis and angle)
Scale 3D scaling factor
Transform a full 3D transform (scale, rotation, translation)
Translation a translation by 3D vector
OrtographicCamera a parallel projection from a viewpoint
PerspectiveCamera a perspective projection from a viewpoint
DirectionalLight a light source with rays parallel to a 3D vector
PointLight a light source at a fixed 3D location
SpotLight a light source with rays inside a cone
HTML version of Basic Foils prepared 7 October 97

Foil 19 VRML - Nodes IV

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Group nodes
Group base class for all group nodes
Separator encapsulates traversal state by push/pop
Switch restricts traversal to one of its children
TransformSeparator separator for transformation subspace
WWWAnchor attaches URL link to a node or group of nodes
Inline node
WWWInline URL to a scene graph to be "inlined"
HTML version of Basic Foils prepared 7 October 97

Foil 20 VRML - Example

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
HTML version of Basic Foils prepared 7 October 97

Foil 21 VRML - Tools

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Browsers:
The browser is a program which reads and renders the VRML file. There are multiple available VRML browsers. Some of them are listed below:
AmberGL VRML Browser v1.0, Fountain (AKA Caligari worldSpace), GLView, i3D, NAVFlyer, Pueblo Beta Client, Virtus Voyager, VR Scout, VRealm, VRweb, WebFX, WebOOGL, WebSpace, WebView
Modelers:
The modeler is a program which can be used to create three-dimensional objects or scenes. List of available modelers supporting VRML includes:
ClayWorks, Ez3d Modeler, Fountain/Caligari worldSpace, G Web, Home Space Builder, Medit, Spinner, STRATA StudioPro Blitz, TriSpectives, Virtus WalkThrough Pro, WebSpace Author, World Builder
HTML version of Basic Foils prepared 7 October 97

Foil 22 VRML - Browsers

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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VRML browser adopts VRML ascii file (gz compressed) as the communication medium and renders the scene. The MIME type for VRML is x-world/x-vrml
The data may be received by the VRML browser itself or by the HTML browser.
Possible methods of VRML browser integration:
  • helper application - data is received by HTML browser and is sent to the VRML viewer.
  • stand-alone application - the viewer is able to receive the data itself.
  • integrated application - the HTML and VRML browsers are integrated
HTML version of Basic Foils prepared 7 October 97

Foil 23 VRML - Browsers II

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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History
  • The very first 3D-Web browser was written by Tony Parisi & Mark Pesce in early 1994.
  • The first commercial browser: WebSpace - by Silicon Graphics
  • The publication of source code for VRML parsers by Silicon Graphics in late 1994 caused involvement of multiple companies in the process of developing VRML browsers.
Current status
  • Commercial and public domain browsers are currently available for almost all platforms
Limitations
  • Browsers differ in their support of VRML features such as LOD, Texture-Mapping, and WWW-Anchor. As the result not all VRML worlds can be viewed on all browsers.
HTML version of Basic Foils prepared 7 October 97

Foil 24 VRML Browsers - Examples I -- WebSpace

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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WebSpace was released as the first commercial browser. It is joint project of Silicon Graphics, Inc. and Template Graphics Software, Inc.
It is built on the Open Inventor platform.
It supports dynamic render culling, Level-Of-Detail, WWW-inlines, and texture mapping.
The WWW-inline nodes can be local files or URL-s.
Texture mapping is fully supported including in-file texture data and URL pointers. The graphics accepted file formats are RGB, JPG, and GIF.
The source code of this browser is not available
HTML version of Basic Foils prepared 7 October 97

Foil 25 VRML Browsers - Examples II -- SDSC WebView

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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This browser has been developed by the San Diego Supercomputer Center. This is a publicly available VRML browser for SGI and UNIX platforms. It is based on Open GL and Open Inventor formats. It supports most of the VRML 1.0 specification. The source code is publicly available.
It cannot handle Textures as URL. The only texture format that it recognizes is SGI RGB. There are also problems with Level-Of-Detail nodes.
HTML version of Basic Foils prepared 7 October 97

Foil 26 VRML Browsers - Examples III -- VRWeb

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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This browser was developed in a joint effort involving IICM (Austria), NCSA, and the University of Minnesota.
It is publicly available for Unix, SGI, & Windows platforms.
The source code for this browser is available.
These browsers mostly run on the Mesa Library which is of OpenGL type. However, there are OpenGL versions of VRWeb for SGI, DEC Alpha, and Windows NT.
This browser supports most of the VRML 1.0
WWW Inline is not supported on the WWW Version, although is supported in the Hyper-G version.
Textures as URL are not supported
HTML version of Basic Foils prepared 7 October 97

Foil 27 VRML Browsers - Examples IV -- WebFX

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Developed by Papersoftware Inc., WebFX plug-in allows rendering of VRML images as embedded objects in Web Browsers such as Netscape.
The stand-alone VRML browser for the Windows - WebFX explorer is also available.
It supports most of the features of VRML 1.0.
Multiple texture formats are supported: GIF, JPG, BMP, RGB, and RAS.
Provides extensions for collision detection, sound, and animated textures.
WebFX is currently available only for the Windows platform and in the near future it is not expected to support any other platform except Macintosh.
HTML version of Basic Foils prepared 7 October 97

Foil 28 Illustra Database System - Server

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The Illustra Server is an Object-Relational DBMS (ORDBMS)
It supports Object-Oriented management of rich data types, and at the same time provides an efficient query language based on extensions to industry-standard SQL.
Illustra Server efficiently handles alphanumeric, character, and text data, video, images, and documents within a single repository.
HTML version of Basic Foils prepared 7 October 97

Foil 29 Illustra - Evolution in DBMS

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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HTML version of Basic Foils prepared 7 October 97

Foil 30 Illustra Database System
Object-Relational DBMS

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The features typical of Relational DBMS:
  • Data access via standard SQL
  • Standard security controls
  • Full server-enforced data integrity
  • Transactions and recovery
  • Performance and scalability
Features typical of object-oriented database technologies:
  • Ability to create any data types
  • Optimized access to rich data types
  • Encapsulation, inheritance, polymorphism
HTML version of Basic Foils prepared 7 October 97

Foil 31 Illustra Database System - DataBlades

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The Illustra Server provides an extensible platform for storage and retrieval of objects.
Object extensions - DataBlades - plug intelligence into Illustra for specific kinds of data, extending the SQL language allowing to manage the data required by a specific application.
DataBlade modules can be self-contained or can take advantage of data types and functions defined by other DataBlade modules.
HTML version of Basic Foils prepared 7 October 97

Foil 32 Illustra Database System
DataBlades (cont.)

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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DataBlades provide specialized support for some application domains
DataBlades consist of several components:
  • data types
  • functions (SQL or C)
  • rules and alerters
  • tables
New types can be treated as standard built-in system types
Functions defined in DataBlade can be executed on the client or on the server site
HTML version of Basic Foils prepared 7 October 97

Foil 33 Illustra - System Architecture

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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HTML version of Basic Foils prepared 7 October 97

Foil 34 Illustra Database System --
2D Spatial DataBlade

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The 2D Spatial DataBlade module defines 10 new data types that describe planar geometric shapes and polygons.
The following objects can be represented:
    • - circle
    • - directed graph
    • - ellipse
    • - line segment
    • - path
    • - point
    • - polygon
    • - polygon set
    • - quadrangle
    • - square/rectangle
HTML version of Basic Foils prepared 7 October 97

Foil 35 Illustra Database System --
3D Spatial DataBlade

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The 3D Spatial DataBlade module adds support for data in three dimensional space.
It defines 18 new data types:
    • - 3D unit vector
    • - 3D vector
    • - 3D box
    • - circle
    • - circular arc
    • - ellipse
    • - line segment
    • - path
    • - point and ECS point
HTML version of Basic Foils prepared 7 October 97

Foil 36 Illustra Database System
Access to the Data

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Data can be accessed in various ways:
SQL - Unix or MSWindows Client
API - LIBMI - C library:
  • - processing SQL queries
  • - direct access
HTML version of Basic Foils prepared 7 October 97

Foil 37 Database Support for VRML

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The goal is to store data in rich semantic format in a database system and dynamic synthesize VRML worlds on request from the user.
Final form (VRML) is created in real-time using data stored in the database and user-defined parameters of data selection and VRML creation.
HTML version of Basic Foils prepared 7 October 97

Foil 38 Why Database Support for VRML ?

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Database system is used to store the data
  • fast retrieval of data (indexing)
  • language to query and manipulate data
  • simultaneous access by multiple users
Database keeps information about the components - not the final VRML form - semantic modeling
  • easy and powerful update
  • more compact storage
VRML representation is created dynamically
  • result is up-to-date
  • multiple views on the same data are possible
  • queries can select parts of the data
HTML version of Basic Foils prepared 7 October 97

Foil 39 Standard VRML Storage
Characteristics

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Data is stored as ASCII in text files
The files can be accessed locally or through WWW
Files may include other files (Inline)
Some of the objects can represent links to other VRML or HTML pages
HTML version of Basic Foils prepared 7 October 97

Foil 40 Standard VRML Storage
Disadvantages

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Only the geometrical information is available
User cannot specify what parts/kind of data he/she needs - no queries possible
The whole world description must be sent
No possibility of changing parameters of the world creation
HTML version of Basic Foils prepared 7 October 97

Foil 41 Geometrical vs. Semantical Model

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Geometrical description
only geometrical information
no composition structure
no identity of components (e.g. name)
no type information
only geometrical queries possible
multiversion visualization not possible
HTML version of Basic Foils prepared 7 October 97

Foil 42 System Architecture

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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HTML version of Basic Foils prepared 7 October 97

Foil 43 VRML Synthesis

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Synthesis of VRML representation can be divided into two separate parts:
  • generation of terrain shape
  • generation of object description
Why terrain shape description is treated in a special way ?
  • very specialized and optimized VRML object
  • constant - user does not edit the terrain data
  • very big in volume - special mechanisms assure efficient storage and fast retrieval
  • high number of specific parameters
HTML version of Basic Foils prepared 7 October 97

Foil 44 Terrain Data

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Data used for terrain shape modeling
  • 100 meters DEM (Digital Elevation Model) data
  • 30 meters color data - satellite image
Values of three color components (RGB) are calculated using six original values: three from the visible range and three infrared.
HTML version of Basic Foils prepared 7 October 97

Foil 45 Synthesis of Terrain Description

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Data is stored in the database in "raw" format - values describing altitude and color of each point separately.
In this form the data is retrieved by the conversion program.
New node of VRML 1.1 - ElevationGrid - is used
Conversion program produces the VRML representation using parameter values given by user.
The parameters the user can set include:
  • color or monochrome option
  • lighting option
  • color corrections
  • altitude magnification (default=2)
  • maximum resolution
HTML version of Basic Foils prepared 7 October 97

Foil 46 Creation of VRML files

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The creation of VRML files is automatic.
Surface is modeled in parts.
The elevation data is transformed to a set of points.
The color data defines colors of particular points.
The points are linked to obtain surfaces.
The resolution of a particular part may vary depending on the maximum resolution requested by the user and the distance from the viewpoint.
HTML version of Basic Foils prepared 7 October 97

Foil 47 VRML modeling

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The following VRML structures are used to model the terrain data:
  • - QuadMesh - basic shape representing the surface, it is
  • an Open Inventor equivalent of VRML 1.1 ElevationGrid
  • - Multivalued Material nodes - define colors of points,
  • - LOD - Level-Of-Detail node - specifies portions of data
  • to be loaded with different resolution levels depending
  • on the distance from the viewpoint,
  • - WWWInline enables loading of scene in portions,
  • - WWWAnchor - allows linking with HTML description
  • pages
  • - DirectionalLight - lighting in the scene.
HTML version of Basic Foils prepared 7 October 97

Foil 48 LOD - Level-Of-Detail

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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LOD - Level-Of-Detail is a group node used to allow applications switching between various representations of objects.
The child nodes of LOD represent the same object at varying levels of detail.
Which child node is used for the representation of specified object depends on the distance between this object and camera.
The representations for higher distances have lower resolution.
Use of LOD reduces the number of polygons to be displayed and increases the rendering speed.
HTML version of Basic Foils prepared 7 October 97

Foil 49 Level-Of-Detail - Example

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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Various detail levels are achieved by creating various descriptions for each part of the surface using different resolutions (see pics).
The left picture shows an area of 21x21 points in full resolution. The right picture shows the same area with resolution 5x5 points.
HTML version of Basic Foils prepared 7 October 97

Foil 50 Colors

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The system uses 24-bit color.
The color is information is obtained from the satellite images.
The color is defined for each point separately using Material node.
The color of a surface connecting points of different colors is interpolated.
This solution is 2-5 times faster than the texture mapping and looks better.
HTML version of Basic Foils prepared 7 October 97

Foil 51 Data Storage and Indexing

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
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The terrain data is stored in one table with types optimized for the speed of retrieval.
Each row of the table describes one point.
To improve retrieval speed of the data, various kinds of indices have been set.
The indices are optimized for fast retrieval of square parts of terrain data using various resolution levels.
HTML version of Basic Foils prepared 7 October 97

Foil 52 Reducing Number of Polygons

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Reduction of polygons number to be rendered in one scene is crucial for the performance
Reduction can be static or dynamic
Static reduction is achieved by decreasing the resolution
Dynamic reduction uses the Level-of-Detail feature
Dynamic reduction can is achieved in two stages:
  • by presenting the same region with different resolution levels
  • by gathering multiple regions into bigger areas
HTML version of Basic Foils prepared 7 October 97

Foil 53 Multi Resolution Terrain Model - I

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
HTML version of Basic Foils prepared 7 October 97

Foil 54 Multi Resolution Terrain Model- II

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
HTML version of Basic Foils prepared 7 October 97

Foil 55 Modeling of Objects - Object Data

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Additional data can be represented as "objects"
Objects correspond to real world entities
Description of objects includes:
  • type of object
  • position (x,y,z coordinates)
  • orientation
  • scale
HTML version of Basic Foils prepared 7 October 97

Foil 56 Modeling of Objects - Types

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Types define the properties of objects
Types are named
Types may be simple or composite
Simple types are VRML description
Composite types are built using simple types and transformations
Transformation defines:
  • position
  • orientation
  • scale
  • color
HTML version of Basic Foils prepared 7 October 97

Foil 57 Definition of Objects - Example

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
HTML version of Basic Foils prepared 7 October 97

Foil 58 Database Schema

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
HTML version of Basic Foils prepared 7 October 97

Foil 59 Multiversion Approach

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
Multiversion approach enables to visualize the same data in various ways.
Versions correspond to the rules of creation of VRML (types) not the objects.
Multiversion enables to create VRML in various ways depending on the client's needs and preferences (e.g. with various levels of detail, including or excluding some types etc.)
HTML version of Basic Foils prepared 7 October 97

Foil 60 Multiversion Approach

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
The hierarchy of versions is defined by the version graph
Child version while created inherits all parent's properties - easy creation of new versions
Only differences between parent and child version are stored - no redundancy
Multiple inheritance possible
Propagation of changes made in parent versions
HTML version of Basic Foils prepared 7 October 97

Foil 61 Terrain rendering in VRML - Example I

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
HTML version of Basic Foils prepared 7 October 97

Foil 62 Terrain rendering in VRML - Example II

From VRML and Use of Databases as backend and Application to GIS ARL Database Tutorial -- February 98. *
Full HTML Index
© on Mon Oct 13 1997