Tour 3D

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Introduction

This piece is meant to be used for an introductory demo to 3D technologies, in particular with respect to 3D contents on the Web, 3D applications that use the Internet, and 3D models that share over the Internet.

3D Computer graphics is done in many areas, e.g. design, engineering, computer science, and the arts. Also, there exist many technical fields. This tour is definitly biased...

3D and the Internet

On the Internet, 3D is used in many ways:

(1) Multi-user worlds and games

Various virtual environments usually use special clients, i.e. software that you need to install) and that use various Internet transport and application layers. Typical examples are:

• Virtual worlds like Second Life and 3D chat rooms
• Massive multiplayer games
• Virtual mapping tools like Google Earth
• 3D modeling software that allows for real-time multi-user editing

(2) 3D contents and environments on the web

Some 3D contents are available through the world-wide web, i.e. in your browser. Web 3D technology includes:

• Browser plugins for 3D formats like X3D or general purpose formats like Flash 3D or Java 3D. There exist many vendor-specific formats and plugins.
• Recent WebGL technology, i.e. a 3D low-level 3D graphics API

Typical examples include:

• Interactive 3D models such as Google Body
• Educational visualizations of buildings or science models
• Data visualizations
• A few virtual worlds and games

(3) The web for sharing 3D models and applications

The Web is used to share and distribute 3D models and applications

• Any file(s) can be shared over the web, but this applies in particular to various kinds of Computer-aided design and manufacturing models for which software repositories exist.

We shall demonstrate examples of each kind later.

Introduction to computer graphics

Four main stages:

1. Modelling
2. Adding animation and interactivity
3. Layout and inserting into a larger scene
4. Rendering (displaying)

We shall shortly introduce various aspects of these stages below

Modelling principles

Most 3D models rely on a so-called wire frame model, i.e. mathematical model that describes their surface with points, lines and surfaces, also called vertices, edges and faces (Boundary Representations)

Sample rendering of a wireframe cube, icosahedron, and approximate sphere (Wikipedia)

Wireframe models in Internet 3D often "just" define triangles that make up the outside of a closed polyhedron. A Polyhedron is a 3D closed (watertight) geometric object with flat faces and straight edges. However, more sophistic models also can be described with lines and surfaces that are not straight (though the final model used may be rendered as polyhedron made up of lots of triangles.

Let's have a look at a little duck. It's made of 2108 dots (vertices) and 4212 faces. Most of these can be found in its eyes and mouth.

A 3D duck with a coordinate system

To create such models various strategies may be used:

• 3D Drawing/modeling programs to draw points lines and surfaces that then can be connected. All of these programs also allow to transform surfaces in various ways, e.g.
  • by CSG (see below)
  • by manipulation of meshes (e.g. pull out a surface, subdivide and pull/push)
• Constructive Solid Geometry (CSG) programs allow to create and object by adding building blocks and also by using a building block to substract volumes.
• Mathematical synthesis with formulas
• 3D scanning and 3D imagery
• ....

Boundary representation

As we said before, most 3D models can be represented by points, lines and triangles made up from these points and lines. These models also can be called meshes.

The Meshlab duck in various rendering modes

Points (vertices)	Visible parts of the wireframe	Full wireframe view
Wireframe + solid surfaces (triangles)	Solid surface (smoothed)	Textured with a jpg
Phong shaded + some extra tricks	Phong shaded	Showing the vertices and face normals

DEMO (Software) of Meshlab. “MeshLab is an open source, portable, and extensible system for the processing and editing of unstructured 3D triangular meshes. The system is aimed to help the processing of the typical not-so-small unstructured models arising in 3D scanning, providing a set of tools for editing, cleaning, healing, inspecting, rendering and converting this kind of meshes.” In more simple terms, Meshlab is not a 3D drawing program, but it can be used to manipulate and render meshes in various ways.

Animation

Computer animation means generating animated images by using computer graphics. Technically speaking, animation just displays various "pictures" over time (about 24 frames/second). But from a modellers point of view, most animations are now created through some sort of manipulable skeletons.

Let's have a look at avatars, i.e. some kind of "puppets" that are used in various application areas such as video games and virtual worlds. One popular technology defines an avatar as:

• skeleton that is composed of connected bones representing various body parts
• a skin

Sometimes avatar movement is obtained through studying or capturing living persons.

Rendering

Can be either

• Realtime
• Photorealistic (not real-time)

“In this illustration of crystal structure, the virtual photo studio surrounding the reflective balls includes an umbrella light and studio camera” (wikipedia)

Stacked balls with "camera and studio light" wikipedia

• Rendering will take into account light(s) and other paramters.
• Various materials reflect lights and colors in a different way.

3D Printing

....

Application areas

Below we show a few examples of application areas, several of which may share the same technologies.

Industrial design

CAD/CAM

Movies

“Computer-generated imagery (CGI) is the application of the field of computer graphics or, more specifically, 3D computer graphics to special effects in art, films, television programs, commercials, simulators and simulation generally, and printed media. The visual scenes may be either dynamic or static.” (Wikipedia)

• First movies that used 3D were Westworld (1973) and Futureworld (1976).

Medecine

Several areas:

• Medical imagery

CRT scans etc.

• Anatomical models for training

DEMO (WebGLO) Google body browser. Read this how to

DEMO (YouTube video]) Google Body Browser (many others)

Alternatives: Visible human project, 3D Indiana

• Computer-assisted surgery

Virtual worlds

Key items:

• The first textural and 2D environments were created in the 1980's.

DEMO (YouTube video) Lucasfilm's Habitat Promotional Video

• The first 3D virtual worlds on the Internet appeared in the mid-1990's
• The first well-known commercial virtual world is Active Worlds
• Today's best known environment is Second Life

Games

Games are built using so-called game engines

Links

• A Critical History of Computer Graphics and Animation by Wayne Carlson