Computer Graphics/and Multimedia CMM472/CIT773 What is CG ?, History of CG, Course Overview

Applied Computer Science and Multimedia, SIE&T2 Introduction Story of CG –Producing image using computer –40 years ago : display a few line on CRT –Now generated images are indistinguishable from photographs

Applied Computer Science and Multimedia, SIE&T3 Application of CG Depends on the user community need Advance of hardware and software Area of CG –Display information –Design –Simulation –User interface

Applied Computer Science and Multimedia, SIE&T4 Display Information Classical using spoken and written language Drawing field –Babylonians (4000 years ago) use stone for floor plan –Greek (2000 years ago) till Renaissance Has idea of architecture graphically –Before today use manual drafting and drawing –Today : computer based system Able to develop and manipulated in real-time

Graph and Charts Applied Computer Science and Multimedia, SIE&T5

Information as spreadsheet Applied Computer Science and Multimedia, SIE&T6

7 CG Applications Statistic –100 years : explored the techniques for plotting data –Now, computer plotting package provided variety of technique, color tools etc. Medicine –Interested in data-analysis problems –Image technology, CT, MRI, Ultrasound, PET

Applied Computer Science and Multimedia, SIE&T8 Patient having MRI scan Example of MRI scan result

Ultrasound Applied Computer Science and Multimedia, SIE&T9 2D ultrasound

Ultrasound con’t Applied Computer Science and Multimedia, SIE&T10 3D - ultrasound

Applied Computer Science and Multimedia, SIE&T11 Design Engineer, architecture using CAD –Iterative process for best or optimize solution –Ex. Mechanical parts, VLSI etc. CAD package has interactive tools ex. menu, tool bar –interactive interface and analyze etc. –Able to generate different image, different view

CAD-example Applied Computer Science and Multimedia, SIE&T12

Applied Computer Science and Multimedia, SIE&T13

Applied Computer Science and Multimedia, SIE&T14

Applied Computer Science and Multimedia, SIE&T15 Simulation Refer to capable of generating images in real-time Applied with advance hardware Ex. Training Pilot, Flight simulator Some special VLSI chip able to generate sophisticate game Photo realistic movie Together with headset led her has stereoscopic effect by different view for each eye

Applied Computer Science and Multimedia, SIE&T16 User Interface GUI from OS like MS windows, X windows, Macintosh OS Use of menu and icon, mouse Different only in detail

Applied Computer Science and Multimedia, SIE&T17 Graphical System 5 major elements –Processor, memory, frame buffer, output devices and input devices General for every system

Computer art Applied Computer Science and Multimedia, SIE&T18

Applied Computer Science and Multimedia, SIE&T19 Pixel and Frame buffer Picture is produced as array of pixel (raster) Pixel are stored in Frame buffer memory : VRAM for fast redisplay Depth : number of bits for each pixel –24 bit has true color system : RGB system Resolution : number of pixel in frame buffer

Applied Computer Science and Multimedia, SIE&T20 Detail of area around one eye showing individual pixel. Pixels. Image of Yeti the cat

Applied Computer Science and Multimedia, SIE&T21 Output Device Domain type : CRT display Computer convert display signal from digital to analog to control plate Refresh rate : rate for retrace the screen at least 50 times per second The cathode-ray tube (CRT)

Applied Computer Science and Multimedia, SIE&T22 2 systems for refresh rate In order to avoid flicker of display Interlace display : –Odd row and even row are refresh alternately Noninterlace display –Display scan in one time row by row

Applied Computer Science and Multimedia, SIE&T23 Color display system Shadow-mask CRT

Applied Computer Science and Multimedia, SIE&T24 Images Computer generate synthetic images Lighting, shading and properties involve many aspect of image formation

Applied Computer Science and Multimedia, SIE&T25 Object and Viewers in CG Object references –Shape referred by object point to reference coordinate system –Position –Geometric primitives : eg. point, line etc. Viewer One who observe object ( man, camera etc.) The same object different image for different place

Applied Computer Science and Multimedia, SIE&T26 A’s view B’s view C’s view Image seen by three different viewers

Applied Computer Science and Multimedia, SIE&T27 Image forming in real camera Viewer and object are both in 3D system but the formed image is 2D

Applied Computer Science and Multimedia, SIE&T28 Light and Images Make an image more realistic Light from source strike and reflect from object enter the camera give some surface detail to the viewer A camera system with a light source

Applied Computer Science and Multimedia, SIE&T29 Ray tracing The strike and illuminate ray that interact the object surface is the ray that make an image to viewer Scene with single point source

Applied Computer Science and Multimedia, SIE&T30 Ray tracing A B C D E F

Applied Computer Science and Multimedia, SIE&T31 Source of light Light travels in straight line to object Point source –Light from single location emit equally in all direction Light bulb –Emitting over an area, more in one direction More sources can be modeled by a number of point sources Monochromatic light : source of single frequency

Applied Computer Science and Multimedia, SIE&T32 Receptor: Human Visual system Extremely complex Response to 350 nm to 780 nm light Sensor :3 type cone cell and 1 type of rod cell The human visual system

Resolution : how large object size that can see Intensity: the measure of light energy Brightness : how perceive intense light that emitted form object Eyes do not have the same response like monochromatic –Red light and green light with same intensity have different to us

Applied Computer Science and Multimedia, SIE&T34 CIE standard observer curve Cone sensitivity

Applied Computer Science and Multimedia, SIE&T35 Pinhole Camera: How image build on projection plane Simple geometric model to understand how image contribute Pinhole camera Side view of pinhole camera

Properties –Infinite depth of field Disadvantage –Admits only single ray –Unable to adjust to different angle of view  view angle

Applied Computer Science and Multimedia, SIE&T37 The synthetic camera model Learn to understand that the specification of the object is different from the viewer Imaging system

Applied Computer Science and Multimedia, SIE&T38 Equivalent views of image formation (a) With image formed on the back of camera (b) With image plane move in front of the camera

Applied Computer Science and Multimedia, SIE&T39 Imaging with the synthetic camera

Applied Computer Science and Multimedia, SIE&T40 Image Clipping Clipping (a) with window in initial position, and (b) with window shifted.

Applied Computer Science and Multimedia, SIE&T41 Application Programmer Interface

Applied Computer Science and Multimedia, SIE&T42 Application model for programmer Application programmer’s model of software

Set of function reside in a graphics library API should match the conceptual model that the user wish to employ to the specific images Available API: OpenGL, PHIGS, Direct3D, VRML and JAVA-3D Specification of the synthetic camera model –Objects –Viewer –Light source –Material Properties

Applied Computer Science and Multimedia, SIE&T44 Modeling - Rendering Renderer duty –Adding light source –Material properties –Other detail effect The modeling-rendering pipeline

Applied Computer Science and Multimedia, SIE&T45 Graphic Architecture Information had to be sent with high enough rate to avoid flicker Early graphics system

Applied Computer Science and Multimedia, SIE&T46 Display Processor Display-processor architecture

Applied Computer Science and Multimedia, SIE&T47 Pipeline: arithmetic processing pipeline Arithmetic pipeline

Applied Computer Science and Multimedia, SIE&T48 Object processed geometry Geometric pipeline Convert the object coordinate system to display system Limit the image part on display Project 3D object into 2D on display 2D image converted to pixel and store at frame buffer

Applied Computer Science and Multimedia, SIE&T49 Performance characteristic Pipeline architecture Floating point VLSI chip : able to do 4*4 matrix