1. Computer Graphics- SCC 342 Chapter 3: Computer Graphics Software Dr. Doaa Hegazy

2. Two broad categories: – Special purpose packages (e.g. CAD systems and painting programs) – General programming packages (e.g. Graphics Library (GL), OpenGL, Virtual Reality Modeling Language (VRML), Java2D, Java3D Computer Graphics Application Programming Interface (CG API)

3. 3.1 Coordinate Representations General graphics packages require geometric descriptions to be specified in a standard, right handed, Cartesian-coordinate reference frame The right-handed Cartesian coordinate system indicating the coordinate plane Images source:http://en.wikipedia.org/wiki/Cartesian_coordinate_system

4. 3.1 Coordinate Representations

5. Modeling Coordinates (local or master coordinates) World coordinates Viewing coordinates Projection coordinates Normalized Coordinates Device coordinates

6. 3.2 Graphics Functions The routines in graphics packages cab be classified as functions for: – Graphics output primitives: building block for any picture (lines, circles etc.) – Attribute: properties of output primitives – Geometric transformations: change size, scale and orientation of output primitives – Modeling transformations: modeling complex objects

7. 3.2 Graphics Functions The routines in graphics packages cab be classified as functions for: – Viewing transformations: select view of the scene, type of projection to be used, location on the display screen – Input functions: control the flow of data from interactive input devices – Control operations: housekeeping functions such as clearing screen area or initialize parameters

8. 3.3 Software Standards Primary goal of standardizing: Portability Graphical kernel system (GKS) 1984: the first graphics SW standard – adopted by International Standard Organization (ISO) and ANSI Programmer’s Hierarchical Interactive Graphics Systems (PHIGS): the second graphics SW standard – increased capabilities for hierarchical modeling

9. 3.3 Software Standards Graphics work stations from Silicon Graphics Inc. (SCI): became increasingly popular with the development of GKS and PHIGS Graphics Library (GL): set of routines came with the graphics work stations OpenGL: developed in the early 1990s as a HW independent version of GL