1 Chapter 1: Graphics Systems and Models

2 Applications of C. G. – 1/4 Display of information Maps GIS (geographic information system) CT (computer tomography) MRI (magnetic resonance imaging) PET (positron-emission tomography) Fluid flow, molecular biology, mathematics…

3 Display of Information

4 Applications of C. G. – 2/4 Design CAD (computer-aided design): VLSI (very-large-scale integrated) circuits Together with other tools: architecture or interior design

5 Interior Design

6 Applications of C. G. – 3/4 Simulation and animation Flight simulation – pilot training Games and educational software Benefits: Less cost Less danger, e.g. combination with the VR (virtual reality) techniques can help surgical interns and astronauts

7 Applications of C. G. – 4/4 User interfaces Friendly working environment: windows, icons, menus, pointing devices

8 A Graphics System

9 Pixels

10 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

11 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

12 Output Devices – 1/2 CRT (Cathode-ray tube)

13 Output Devices – 2/2 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

14 Shadow-mask CRT

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

16 Images: Physical and Synthetic Image formation Lighting Shading Properties of materials

17 Objects and Viewers – 1/3 Object: formed from geometric primitives Points, lines, polygons Vertex (pl. Vertices) is the most primitive one Viewer: Locations Viewing angles

18 Objects and Viewers – 2/3

19 Objects and Viewers – 3/3 3D world  2D image

20 Light and Images

21 Electromagnetic Spectrum

22 Single Point Light Source

23 Ray Tracing Penetrating transparent surfaces Reflected by Mirrors Diffuse surfaces Refracted Absorbed

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

25 Pinhole Camera – 1/2

26 Pinhole Camera – 2/2  (x p, y p, -d) is the projection of (x, y, z)

27 Synthetic-camera Model – 1/4 Bellows Camera Projector

28 Synthetic-camera Model – 2/4 COP(Center of Projection) Focal Length

29 Synthetic-camera Model – 3/4 Film Plane Projection Plane

30 Synthetic-camera Model – 4/4 Clipping Window

31 Programmer’s Interface Interface for a painting program

32 Application Programmer’s Interface Specifications of the functions in the graphics library

33 Three-dimensional APIs Objects Viewers Light sources Material properties

34 Camera(Viewer) Specifications Position (COP) Orientation Focal length Film plane

35 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…

36 Wireframe

37 Flat Shading

38 Smooth Shading

39 Modeling With Curves/surfaces

40 Bump Mapping

41 Environmental Maps

42 Antialiasing

43 Modeling-rendering Paradigm Example: Scene graph

44 Graphics Architecture – 1/3 Early graphics system Compute line segments Draw line segments Very high rate to avoid flickering

45 Graphics Architecture – 2/3 Display-processor architecture

46 Graphics Architecture – 3/3 Arithmetic pipeline: doubling the throughput! Pipeline Architecture: Geometric pipeline

47 Geometric Pipeline – 1/2 Transformation Conversion between coordinate systems Translation, rotation, scaling Aggregate transforms by matrix multiplications Clipping Could be further pipelined

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

49 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

50 Summary & Notes of Chapter 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