Advanced Graphics Algorithms Ying Zhu Georgia State University Lecture 02 Overview of Computer Graphics Programming

Computer Graphics: A Brief History William Fetter of Boeing coins the term “Computer Graphics” (1960) Basic computer graphics algorithms/concepts are introduced: hidden line detection, homogeneous coordinates, line drawing, back-face culling, parametric curves & surfaces, etc. Spacewars, first video game, is developed at MIT (1961) SketchPad: first interactive computer graphics software (1962) First Head Mounted Display is developed at MIT (1968) Bell Labs builds first frame buffer (3 bits) First use of CGI for commercials – MAGI for IBM (1969) SIGGRAPH is formed (1969) Spacewars Image courtesy MIT Media Lab

Computer Graphics: A Brief History Many fundamental computer graphics algorithms/technologies are introduced: visible surface detection, Gouraud shading, Phone shading, Z-buffer, curved surface rendering, texture mapping, reflectance and environment mapping, anti-aliasing, curved shadow, bump mapping, ray tracing, keyframe based animation, etc. First SIGGRAPH conference (1973) Microsoft is founded (1974); Special effects powerhouse, Industrial Light & Magic, is founded (1975) The first flight simulator for Apple II is released (1978) (later purchased by Microsoft) First flight simulator Image courtesy simflight.com

Computer Graphics: A Brief History Many major companies in the graphics field are founded: Silicon Graphics Inc., ATI, SUN, Pixar, Adobe, AutoDesk, Alias, Softimage, Side Effects, etc. More graphics algorithms are introduced: radiosity, motion capture, motion blur, morphing, etc. The birth of RenderMan (1988) Wavefront – the first commercially available 3D software package (1984) AutoCAD 1.0 (1982) Tron (1982): 1st film to make extensive use of computer graphics Tron

Computer Graphics: A Brief History The release of major 3D graphics libraries: OpenGL, DirectX, Java3D Image based rendering attracts attention The release of major 3D modeling & animation packages: 3D Studio, 3D Studio Max, Maya, etc. The rise and fall of SGI NVIDIA releases first Graphics Processing Unit (1999) Increasing use of 3D special effects in feature films: Terminator 2, Titanic, etc. First 3D computer animated feature film: Toy Story by Pixar The release of Doom and Quake CAVE: immersive virtual environment Titanic

Computer Graphics: A Brief History 2000 – present Powerful Graphics Processing Units on PC graphics card: NVIDIA Geforce3/4/FX/6800/7800/8800, ATI Radeon 9700/9800/X800/X850/X1950 High level shading languages: Cg, HLSL, GLSL, Sh, etc. New generation game console: Xbox/360, Playstation2/3 Widespread use of CGI special effects in feature films: War of the Worlds, Lord of the Rings, Spiderman, Matrix, Finding Nemo, Shrek, The Cars, etc.

Creating 3D Graphics Content Different ways to create graphics content If you want to create non-interactive 3D animations Use graphics modeling/animation tools: 3DS Max, Maya, Blender, etc. If you want to create interactive 3D applications (game, training & simulation program) A combination of both modeling/animation tools and programming C/CPP + scene graph + OpenGL/D3D + Shader

Graphics Libraries (APIs) 3D graphics applications are built on top of graphics libraries A collection of graphics routines that an application program can call The APIs hide the underlying complexity of graphics hardware and/or lower level APIs Large scale graphics applications are usually built on top of high level graphics APIs

Graphics Libraries (APIs) High level APIs are implemented on top of low level graphics APIs Low level APIs control graphics hardware through graphics drivers Between low level graphics APIs and graphics drivers there are shader libraries

High Level Graphics APIs Also known as Scene Graph APIs Non-real-time oriented APIs Java3D VRML & X3D Open Inventor Renderman

High Level Graphics APIs Real-time oriented APIs 3D graphics and game engines Torque Game Engine OGRE OpenGL Performer Open Scene Graph OpenSG Many proprietary high level APIs

Game Engines Game engine Graphics API designed specifically for game development Contains all non-content related functions/elements

Game Engine Game Architecture Gameplay Game engine Tools & Editor Graphics Hardware

Modern Game Engine Features Scene management Culling, Rendering Bump mapping Shadow Collision Decals AI Particle systems, etc. Shader management

Game Engines There are hundreds of game engines Most popular game engines Torque Game Engine (commercial) OGRE (open source) For a comprehensive list, check out http://www.devmaster.net/engines/

Torque Game Engine A very popular game engine with multi-player network code, indoor/outdoor rendering engines, skeletal animation, drag and drop GUI creation, a built in world editor, and a C- like scripting language. http://www.garagegames.com/

OGRE Object-oriented Graphics Rendering Engine A scene-oriented, flexible 3D engine written in C++ designed to make it easier and more intuitive for developers to produce games and demos using 3D hardware. http://www.ogre3d.org/

OGRE example

OGRE example

Java3D High level object-oriented scene graph API https://java3d.dev.java.net/ http://www.j3d.org/ Platform independent, implemented on top of Direct3D or OpenGL Try to meet a wide variety of application requirements Real-time performance Object modeling Input devices support Stereoscopic vision

JOGL Java OpenGL (JOGL) https://jogl.dev.java.net/ A wrapper library that allows OpenGL to be used in the Java programming language

VRML & X3D VRML = Virtual Reality Modeling Language X3D HTML like language for describing 3D shapes and interaction X3D Next generation open standard for 3D on the web Officially replaced VRML in July 2004 X3D supports XML for tight integration with Web technologies and tools http://www.web3d.org/

OpenGL Performer http://www.sgi.com/products/software/perfor mer/ A graphics API developed by SGI for real-time visual simulation and other performance oriented applications Implemented on top of OpenGL, with performance as the first priority http://www.sgi.com/products/software/perfor mer/ Performer has great influence on other real-time graphics APIs E.g. Open Scene Graph (http://www.openscenegraph.org/projects/osg)

Why so many scene graph APIs & game engines? Different target applications Real-time vs. non-real-time applications Application specific optimizations Application specific entities E.g. different game genres require different game engines

Why so many scene graph APIs & game engines? Language and platform considerations Platform specific optimizations Open source vs. proprietary APIs Integration of new technologies Not necessarily a good thing Lack of documents & sample code

Low Level Graphics APIs Directly handles 3D rendering Very efficient implementation Only two major low level 3D graphics APIs OpenGL Direct3D (part of DirectX) Comparison of Direct3D and OpenGL http://en.wikipedia.org/wiki/Comparison_of_Direc t3D_and_OpenGL

Direct3D Part of Microsoft’s DirectX libraries Including Direct3D, DirectInput, DirectSound, etc. Designed for real-time graphics applications Computer game Home entertainment Primary choice for game development Latest version is DirectX 10 http://www.microsoft.com/windows/directx/default.aspx Only supported on MS Windows platform

Using Direct3D Benefits Drawbacks Supported by most of the graphics hardware Better game support Better integration with other MS stuff (e.g. .Net) Maintained by one single company Quick to add new features to Direct3D Drawbacks Somewhat more difficult to learn than OpenGL Windows only

OpenGL Platform independent graphics API Window system independent MS Windows, Linux, IRIX, Solaris, Mac, etc. Window system independent MS Windows, X Window Maintained by KHRONOS group (an industry consortium) Members include 3Dlabs, AMD, NVIDIA, Intel, Google, etc. Current specification: OpenGL 3.0 http://www.khronos.org/opengl/

Using OpenGL Benefits Drawbacks http://www.opengl.org/ Open standard Supported by all the graphics cards Supported by all the platforms Lots of books, tutorials, and samples available Most of the mainstream 3D graphics textbooks use OpenGL Drawbacks Historically, OpenGL is often slow to add new features Users are often forced to use OpenGL extensions http://www.opengl.org/

OpenGL Extension OpenGL extensions provide new rendering features above and beyond the features specified in the official OpenGL standard To keep the OpenGL API current with the latest innovations in graphics hardware and rendering algorithms Different kind of extensions: Extensions ratified by the ARB: GL_ARB_multitexture(); Extensions agreed on by multiple vendors: GL_EXT_abgr(); Vendor specific extensions: GL_NV_register_combiners();

OpenGL Extension To find out what OpenGL extensions your graphics card supports, download and install Glview utility (OpenGL extension viewer) http://www.realtech-vr.com/glview/

OpenGL Related APIs GLU (OpenGL Utility Library) Mostly modeling related functions: NURBS, tessellators, etc. Part of OpenGL GLX: connecting OpenGL with X Window WGL: connecting OpenGL with MS Windows

OpenGL Related APIs GLUT (OpenGL Utility Toolkit) implements a simple windowing application programming interface (API) for OpenGL makes it easier to learn OpenGL programming designed for constructing small to medium sized OpenGL programs Binary files: http://www.xmission.com/~nate/glut.html Reference manual: http://www.opengl.org/resources/libraries/glut/spec3/spec 3.html

GPU and Shader Graphics Processing Units are the microprocessors on the newer graphics cards Nvidia, AMD, and Intel are the main GPU vendors You can write programs that runs on GPU using a special programming language These programs are called shaders The programming languages are called shading languages

Shader Programming Why use shaders? Faster and more flexible To implement features that are not available on OpenGL or Direct3D Take advantage of GPU, which is is optimized for graphics applications Faster and more flexible High level shading languages Cg, HLSL, OpenGL SL, Sh Load, compile, and run shader programs from OpenGL or DirectX programs

OpenGL Files OpenGL files comes with MS Windows and/or Visual Studio installation Header files gl.h, glu.h Glut.h (needs to be downloaded) Static libraries Opengl32.lib, glu32.lib glut32.lib (needs to be downloaded) DLLs C:\windows\system32 Opengl32.dll, glu32.dll glut32.dll (needs to be downloaded)

How to compile OpenGL/GLUT programs? http://www.cs.uiowa.edu/~cwyman/classes/fa ll04-22C151/howto/winGLUT.html http://www.cs.unm.edu/~angel/BOOK/INTER ACTIVE_COMPUTER_GRAPHICS/FOURTH _EDITION/vc

Sample OpenGL programs Examples from “OpenGL Programming Guide” http://www.opengl.org/resources/code/samples/r edbook/ OpenGL code samples: http://www.opengl.org/code/ Simple code samples: http://www.opengl.org/resources/code/samples/s imple/

A Simple OpenGL Program (1) #include <GL/glut.h> void display(void) { /* clear all pixels */ glClear (GL_COLOR_BUFFER_BIT); /* draw white polygon (rectangle) with corners at * (0.25, 0.25, 0.0) and (0.75, 0.75, 0.0) */ glColor3f (1.0, 1.0, 1.0); glBegin(GL_POLYGON); glVertex3f (0.25, 0.25, 0.0); glVertex3f (0.75, 0.25, 0.0); glVertex3f (0.75, 0.75, 0.0); glVertex3f (0.25, 0.75, 0.0); glEnd();

A Simple OpenGL Program (2) /* start processing buffered OpenGL routines */ glFlush (); } void init (void) { /* select clearing color */ glClearColor (0.0, 0.0, 0.0, 0.0); /* initialize viewing values */ glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);

A Simple OpenGL Program (3) /* Declare initial window size, position, and display mode (single buffer and RGBA). Open window with "hello" in its title bar. Call initialization routines. Register callback function to display graphics. Enter main loop and process events. */ int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); glutInitWindowSize (250, 250); glutInitWindowPosition (100, 100); glutCreateWindow ("hello"); init (); glutDisplayFunc(display); glutMainLoop(); return 0; /* ANSI C requires main to return int. */ }

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