Introduction to Computer Graphics. Knowledge basic concepts 2D and 3D computer graphics

Transcription

1 Introduction to Computer Graphics Knowledge basic concepts 2D and 3D computer graphics

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3 1 Introduction 2 Basic math 3 2D transformations 4 3D transformations 5 Viewing 6 Primitives 7 Geometry 8 Shading 9 Splines 10 Texture 11 Hidden surfaces 12 Ray-tracing Donald Hearn, M. Pauline Baker, Warren Carithers. Computer Graphics with OpenGL, 4 th edition, Pearson Prentice Hall, paperback

4 Why computer graphics? Visual system offers: Parallel input Parallel processing Computer graphics: ideal for humancomputer communication

5 Applications Graphs and charts Computer-Aided Design Virtual Reality Data Visualization Education and training Computer Art Movies Games Graphical User Interfaces

6 Business graphics

7 Computer-Aided Design AutoDesk IAME 2-stroke race kart engine

8 Computer Aided Design 8

9 Scientific Visualisation To view below and above our visual range 9

10 expression Movies depth of field fracture water motion reflection hair

11 Hardware Fast development History Now: Graphics Processing Unit (GPU), LCD-screen

12 Generating graphics Special-purpose programs Photoshop, Powerpoint, AutoCAD, StudioMax, Maya, Blender, PovRay, General graphics libraries and standards Windows API, OpenGL, Direct3D,

13 Python modeller for POV-Ray

14 Blender

15 Beyond the laptop screen Microsoft Surface Apple ipad

16 Beyond the laptop screen Reality Deck Stony Brook University monitors

17 Beyond the laptop screen Oculus Rift

18 CG standards Set of graphics functions, to be called from programming language Access to and abstract from hardware Standardization Fortran, Pascal, Display Input dev. C, C++, Java, Delphi, Display CG API Drivers Input dev.

19 PHIGS -OpenGL Programmer's Hierarchical Interactive Graphics System) : an API standard for rendering 3D computer graphics, 3D graphics standard for the 1980s through the early 1990s., A combination of features : the rise of OpenGL the most popular professional 3D API of the mid to late 1990s.

20 Software standards GKS (Graphical Kernel System), PHIGS(Programmer's Hierarchical Interactive Graphics System), PHIGS+ (1980-) GL (Graphics Library, SGI) OpenGL (early 1990s) Direct3D (MS), Java3D, VRML,

21 OpenGL 3D (and 2D) Fast Hardware, language, OS, company independent OpenGL architecture review board Broad support Standard graphics terminology

22 Functions Graphics Output Primitives Line, polygon, sphere, Attributes Color, line width, texture, Geometric transformations Modeling, Viewing Shading and illumination Input functions

23 More info on OpenGL The Red Book: Many other web-sites

24 Schematic Model Display Image interaction User

25 Schematic Computer Graphics Model Image Pattern Recognition Image Processing

26 From model to image Model World View NDC Display Graphics pipeline Coordinates and transformations

27 From model to image Model World View NDC Display Cylinder: x 2 + y 2 = r 2 0 z h Local or modeling coordinates Geometric modeling

28 From model to image Model World View NDC Display Position cylinders in scene: World coordinates

29 From model to image Model World View NDC Display Look at cylinders, project on virtual screen Viewing coordinates Visible surfaces, shading

30 From model to image Model World View NDC Display Display: 1 Normalized Device Coordinates 0 1

31 From model to image Model World View NDC Display Display on screen: Device Coordinates 768 Interaction

32 Geometry Stage Modeling: shapes Model Transformation Transformation: viewing Hidden Surface Elimination Shading: reflection and lighting Rasterization Stage 32

33 Rasterization Stage Geometry Stage Rasterization and Sampling Texture Mapping Image Composition Intensity and Colour Quantization Framebuffer/Display

34 An example thro the pipeline The scene we are trying to represent: Images courtesy of Picture Inc.

35 Preparing Shape Models Designed by polygons, parametric curves/surfaces, implicit surfaces and etc. Defined in its own coordinate system

36 Model Transformation Objects put into the scene by applying translation, scaling and rotation Linear transformation called homogeneous transformation is used The location of all the vertices are updated by this transformation

37 Perspective Projection We want to create a picture of the scene viewed from the camera We apply a perspective transformation to convert the 3D coordinates to 2D coordinates of the screen Objects far away appear smaller, closer objects appear bigger

38 Hidden Surface Removal Objects occluded by other objects must not be drawn

39 Rasterization Converts the vertex information output by the geometry pipeline into pixel information needed by the video display Aliasing: distortion artifacts produced when representing a high-resolution signal at a lower resolution. Anti-aliasing : technique to remove aliasing

40 Anti-aliasing Aliased polygons (jagged edges) Anti-aliased polygons