“TIGS: An overview of the terminal independent graphics system” by Heilman and Marchant

TIGS is a general purpose subroutine package providing display generation and interaction capability for a general class of graphics terminals. The package is computer, operating system, and display device independent. Primary design objectives were transportability, maintainability, and ease of use. Features supported by TIGS include line, arc, multi-line plot, test and dot primitives with resettable attributes such as line style, character size, intensity, font, color, transformation matrix, etc. The package uses virtual devices such as locators, keyboards, picking devices and function keys which can represent a wide range of physical devices. TIGS supports modelling transformations, 2D and 3D viewing transformations for clipping and window to viewport mapping. Unlike the GSPC Core System, TIGS uses the interpretive approach which uses a device independent neutral display file. This neutral display file contains information describing all segments, pictures, windows, and viewports in a device independent manner. The file may be saved and used in a later job with a different display device. Additionally, all attributes such as line style, font, character size, etc., can be re-specified without re-defining the contents of a segment. In planning for expansion for distributed graphics applications, multiple independent user coordinate spaces are used. Each coordinate space is called a picture. This allows for re-specification of a window without re-defining the contents of it. A picture and all the segments contained therein can be manipulated as a group. Device independence was implemented by dividing TIGS into a device-independent pre-processor invoked by the applications programmer, and internal device drivers, one per display device. Part of the device driver may reside on a separate processor.

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