1. 1 Computer Graphics Week3 –Graphics & Image Processing

2. Sequence of Images Wireframe Flat shading – HSR (Hidden surface removal) Smooth shading Curves and surfaces – NURBS, Bezier curves/surfaces Texture mapping – Bump mapping, environmental maps, antialiasing… 2

3. Pixels 3

4. A Graphics System 4

5. Frame Buffer High-end systems: VRAM or DRAM Simpler systems: part of memory Depth: the number of bits per pixel True color: depth=24 Resolution: the number of pixels in the frame buffer 5

6. Rasterization or Scan-conversion Conversion of geometric entities to pixels in the frame buffer – High-end systems Special-purpose processors – Simpler systems A single and shared processor 6

7. Output Devices 7 CRT (Cathode-ray tube)

8. Output Devices CRT – Refresh: at least 50 times per second – Interlace and non-interlace systems – Color CRTs have three colored phosphors and a shadow mask Other raster devices: – LCD (liquid-crystal displays) – Plasma panels and digital projection systems – Non-refreshable: printers and plotters 8

9. Shadow-mask CRT 9

10. Input Devices Mouse 10 Joystick Data tablet Anything else? Hand Foot Voice Mind?

11. Images: Physical and Synthetic Image formation – Lighting – Shading – Properties of materials 11

12. Objects and Viewers Object: formed from geometric primitives – Points, lines, polygons – Vertex (pl. Vertices) is the most primitive one Viewer: – Locations – Viewing angles 12

13. Objects and Viewers 13

14. Objects and Viewers 14 3D world  2D image

15. Light and Images 15

16. 16 Synthetic-camera Model Film Plane Projection Plane

17. Single Point Light Source 17

18. Ray Tracing 18 Penetrating transparent surfaces Reflected by Mirrors Diffuse surfaces Refracted Absorbed

19. Human Visual System 19 Visual system does not have the same response to each color. We are most sensitive to green light

20. Pinhole Camera 20

21. Pinhole Camera 21  (x p, y p, -d) is the projection of (x, y, z)

22. Synthetic-camera Model 22 Bellows Camera Projector

23. Synthetic-camera Model 23 COP(Center of Projection) Focal Length

24. Synthetic-camera Model 24 Film Plane Projection Plane

25. Synthetic-camera Model 25 Clipping Window

26. Sequence of Images Wireframe Flat shading – HSR (Hidden surface removal) Smooth shading Curves and surfaces – NURBS, Bezier curves/surfaces Texture mapping – Bump mapping, environmental maps, antialiasing… 26

27. Wireframe 27

28. Flat Shading 28

29. Smooth Shading 29

30. Modeling With Curves/surfaces 30

31. Bump Mapping 31

32. Environmental Maps 32

33. Antialiasing 33

34. Modeling-rendering Paradigm 34 Example: Scene graph

35. Graphics Architecture 35 Early graphics system Compute line segments Draw line segments Very high rate to avoid flickering

36. Graphics Architecture 36 Display-processor architecture

37. Graphics Architecture 37 Arithmetic pipeline: doubling the throughput! Pipeline Architecture: Geometric pipeline

38. Pipelining 38 Arithmetic pipeline: doubling the throughput! Pipeline Architecture: Geometric pipeline

39. Geometric Pipeline Transformation – Conversion between coordinate systems – Translation, rotation, scaling – Aggregate transforms by matrix multiplications Clipping – Could be further pipelined 39

40. Geometric Pipeline Projection – Remaining 3D objects are projected into 2D objects – Parallel or perspective projections Rasterization – Convert 2D objects into pixels 40

41. Performance Characteristics Latency Throughput: – How fast we can move geometric entities through the pipeline – How many pixels per second we can alter in the frame buffer Pipeline architecture is not a must – Ray tracing or radiosity  for better quality 41

42. Summary & Notes of Lecture 1 Application of computer graphics A graphics system Human visual system Pinhole and synthetic camera models Image formation Geometric pipeline Realistic images may require resolution of up to 4000  6000 42