Introduction to Computer Graphics Mohan Sridharan Based on Slides by Edward Angel and Dave Shreiner CS4395: Computer Graphics 1

Overview Slides based on book by Edward Angel and Dave Shreiner: Interactive Computer Graphics, A Top-down Approach with Shader-Based OpenGL (Sixth Edition), Addison-Wesley, Lots of resources on companion website: Some useful resources listed on course website: CS4395: Computer Graphics 2

Objectives Broad introduction to Computer Graphics: – Software. – Hardware. – Applications. Top-down approach: Shader-Based OpenGL compatible with: – OpenGL 3.1 (and later). – Open GL ES 2.0 – webGL CS4395: Computer Graphics 3

Prerequisites Good programming skills in C (or C++). Basic Data Structures: – Linked lists. – Arrays. Geometry. Simple Linear Algebra. CS4395: Computer Graphics 4

Requirements 4-5 programming projects: – Increasing levels of difficulty: totally 65% of grade. – Will move from 2D to 3D with lighting and texture. Term Project: – You pick! – Substantial challenge since it constitutes 25% of grade. Responses + classroom participation: 10% CS4395: Computer Graphics 5

Resources Can run OpenGL on any system: – Windows: check graphics card properties for level of OpenGL supported. – Linux. – Mac: may need extensions for 3.1 equivalence. Get GLUT from web if needed: – Provided on Macs. – freeglut available on web. Get GLEW from web. WebGL: most newer browsers. CS4395: Computer Graphics 6

References – Standards documents, sample code. The OpenGL Programmer’s Guide (the Redbook) 7 th Edition: – The definitive reference. – Mixes 3.0 and 3.1 OpenGL Shading Language, 3 rd Edition. OpenGL ES 2.0 Programming Guide. CS4395: Computer Graphics 7

Outline: Part 1 Part 1: Introduction. Text: Chapter 1. Chapter topics: – What is Computer Graphics? – Applications Areas. – History. – Image formation. – Basic Architecture. CS4395: Computer Graphics 8

Outline: Part 2 Part 2: Basic OpenGL. Text: Chapter 2. Chapter topics: – Architecture. – GLUT. – Simple programs in two and three dimensions. – Basic shaders and GLSL. – Interaction. CS4395: Computer Graphics 9

Outline: Part 3 Part 3: Three-Dimensional Graphics. Text: Chapters 3-5. Chapter Topics: – Geometry. – Transformations. – Homogeneous Coordinates. – Viewing. – Lighting and Shading. CS4395: Computer Graphics 10

Outline: Part 4 Part 4: Implementation. Text: Chapter 6. Chapter topics: – Approaches (object vs. image space). – Implementing the pipeline. – Clipping. – Line drawing. – Polygon Fill. – Display issues (color). CS4395: Computer Graphics 11

Outline: Part 5 Part 5: Discrete Methods. Text: Chapter 7. Chapter topics: – Buffers. – Texture Mapping. – Shader Applications. – Compositing and Transparency. CS4395: Computer Graphics 12

Outline: Part 6 Part 6: Hierarchy and Procedural Methods. Text: Chapters 8-9. Chapter topics: – Tree Structured Models. – Traversal Methods. – Scene Graphs. – Particle Systems. CS4395: Computer Graphics 13

Outline: Part 7 Part 7: Curves and Surfaces. Text: Chapter 10. CS4395: Computer Graphics 14

Outline: Part 8 Part 8: Advanced Rendering. Text: Chapter 11. We are finally done! CS4395: Computer Graphics 15

Extra Lectures Marching Squares. Virtual Trackball. Environment Mapping. Shadows, fractals. Display Issues. Bump Mapping, sampling and aliasing. Reflection and transmission. CS4395: Computer Graphics 16

What is Computer Graphics? CS4395: Computer Graphics 17

Computer Graphics Computer graphics deals with all aspects of creating images with a computer: – Hardware. – Software. – Applications. CS4395: Computer Graphics 18

Example Where did this image come from? What hardware/software did we need to produce it? CS4395: Computer Graphics 19

Preliminary Answer Application: object is an artist’s rendition of the sun for an animation to be shown in a domed environment (planetarium). Software: Maya for modeling and rendering but Maya is built on top of OpenGL. Hardware: PC with graphics card for modeling and rendering. CS4395: Computer Graphics 20

Basic Graphics System CS4395: Computer Graphics 21 Input devices Output device Image formed in frame buffer

CRT Can be used either as a line-drawing device (calligraphic) or to display contents of frame buffer (raster mode) CS4395: Computer Graphics 22

Computer Graphics: Computer graphics goes back to earliest days of computing: – Strip charts. – Pen plotters. – Simple displays using A/D converters to go from computer to calligraphic CRT. Cost of refresh for CRT too high: – Computers slow, expensive, unreliable (not anymore!). CS4395: Computer Graphics 23

Computer Graphics: Wireframe graphics: – Draw only lines! Sketchpad. Display Processors. Storage tube. CS4395: Computer Graphics 24 wireframe representation of sun object

Sketchpad Ivan Sutherland’s PhD thesis at MIT: – Recognized the potential of man-machine interaction. – Loop: Display something. User moves light pen. Computer generates new display. – Sutherland also created many of the now common algorithms for computer graphics. CS4395: Computer Graphics 25

Display Processor Rather than have the host computer try to refresh display, use a special purpose computer called a display processor (DPU). Graphics stored in display list/file on display processor. Host compiles display list and sends to DPU. CS4395: Computer Graphics 26

Direct View Storage Tube Created by Tektronix: – Did not require constant refresh. – Standard interface to computers: Allowed for standard software. Plot3D in Fortran. – Relatively inexpensive: Opened door to use of computer graphics for CAD community. CS4395: Computer Graphics 27

Computer Graphics: Raster Graphics. Beginning of graphics standards. – IFIPS: GKS: European effort. – Becomes ISO 2D standard. Core: North American effort. – 3D but fails to become ISO standard. Workstations and PCs. CS4395: Computer Graphics 28

Raster Graphics Image produced as an array (the raster) of picture elements (pixels) in the frame buffer. CS4395: Computer Graphics 29

Raster Graphics Allows us to go from lines and wire frame images to filled polygons! CS4395: Computer Graphics 30

PCs and Workstations Although we no longer make the distinction between workstations and PCs, they evolved from different roots: – Early workstations characterized by: Networked connection: client-server model. High-level of interactivity. – Early PCs included frame buffer as part of user memory: Easy to change contents and create images. CS4395: Computer Graphics 31

Computer Graphics: Realism comes to computer graphics CS4395: Computer Graphics 32 smooth shadingenvironment mapping bump mapping

Computer Graphics: Special purpose hardware: – Silicon Graphics geometry engine: VLSI implementation of graphics pipeline. Industry-based standards: – PHIGS. – RenderMan. Networked graphics: X Window System. Human-Computer Interface (HCI). CS4395: Computer Graphics 33

Computer Graphics: OpenGL API. Completely computer-generated feature-length movies (Toy Story) are successful. New hardware capabilities: – Texture mapping. – Blending. – Accumulation, stencil buffers. CS4395: Computer Graphics 34

Computer Graphics: Photorealism. Graphics cards for PCs dominate market: Nvidia, ATI. Game boxes and game players determine market direction. Computer graphics routine in movie industry: Maya, Lightwave. Programmable pipelines. CS4395: Computer Graphics 35

What next? Overview of image formation. Overview of graphics architectures. CS4395: Computer Graphics 36