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Computer Graphics- SCC 342 Chapter 3: Computer Graphics Software. Dr. Doaa Hegazy. Two broad categories: Special purpose packages (e.g. CAD systems and painting programs)
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Computer Graphics- SCC 342 Chapter 3: Computer Graphics Software Dr. Doaa Hegazy
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)
3.1 Coordinate Representations • General graphics packages require geometric descriptions to be specified in a standard, right handed, Cartesian-coordinate reference frame Images source:http://en.wikipedia.org/wiki/Cartesian_coordinate_system The right-handed Cartesian coordinate system indicating the coordinate plane
3.1 Coordinate Representations • Modeling Coordinates (local or master coordinates) • World coordinates • Viewing coordinates • Projection coordinates • Normalized Coordinates • Device coordinates
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
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
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
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