Computer Graphics/and Multimedia CMM472/CIT773

1. Computer Graphics/and MultimediaCMM472/CIT773 What is CG ?, History of CG, Course Overview

2. 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&T

3. 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&T

4. 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 Applied Computer Science and Multimedia, SIE&T

5. 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&T

6. 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 Applied Computer Science and Multimedia, SIE&T

7. 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&T

8. 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&T

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

10. 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&T

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

12. 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&T

13. 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&T

14. Color display system Shadow-mask CRT Applied Computer Science and Multimedia, SIE&T

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

16. 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&T

17. Image seen by three different viewers A’s view C’s view B’s view Applied Computer Science and Multimedia, SIE&T

18. 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&T

19. 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&T

20. 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&T

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

22. 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&T

23. 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 Applied Computer Science and Multimedia, SIE&T

24. 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

25. CIE standard observer curve Cone sensitivity Applied Computer Science and Multimedia, SIE&T

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

27. Properties • Infinite depth of field • Disadvantage • Admits only single ray • Unable to adjust to different angle of view q : view angle

28. 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&T

29. 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&T

30. Imaging with the synthetic camera Applied Computer Science and Multimedia, SIE&T

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

32. Application Programmer Interface Applied Computer Science and Multimedia, SIE&T

33. Application model for programmer Application programmer’s model of software Applied Computer Science and Multimedia, SIE&T

34. 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

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

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

37. Display Processor Display-processor architecture Applied Computer Science and Multimedia, SIE&T

38. Pipeline: arithmetic processing pipeline Arithmetic pipeline Applied Computer Science and Multimedia, SIE&T

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

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