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Multiple Types of Graphical Contexts on a Graphics Adapter

IP.com Disclosure Number: IPCOM000122545D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Wood, BR: AUTHOR

Abstract

A 'graphical context' as used below is composed of a set of attributes, a set of drawing primitives, a set of lighting equations, and a set of rules for rendering each drawing primitive. Different types of contexts provide different sets for each of these items, each one tailored to a specific graphical application programming interface (API) or to a specific hardware graphics adapter. For example, colors are supported under X-Windows with two attributes, foreground color and background color. In graPHIGS, colors are supported with many attributes, including polyline color, text color, interior color, edge color, etc.

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Multiple Types of Graphical Contexts on a Graphics Adapter

      A 'graphical context' as used below is composed of a set
of attributes, a set of drawing primitives, a set of lighting
equations, and a set of rules for rendering each drawing primitive.
Different types of contexts provide different sets for each of these
items, each one tailored to a specific graphical application
programming interface (API) or to a specific hardware graphics
adapter. For example, colors are supported under X-Windows with two
attributes, foreground color and background color. In graPHIGS,
colors are supported with many attributes, including polyline color,
text color, interior color, edge color, etc.

      Conventional graphics adapters provide support for only one
type of graphical context. Other types must be 'mapped' into the one
supported type which usually entails trading off performance and/or
function. A reduction in performance occurs when one attribute or
drawing primitive must be 'mapped' into another. For example, to
allow an X-Windows application to run on an adapter tailored to the
graPHIGS graphical context, a call to change the foreground color
attribute must be mapped into many commands to the adapter to change
each of its many color attributes. A trade-off in function occurs
when the graphical context supported by the graphics adapter does not
support the function provided by the software API being mapped onto
the adapter.  An API providing spot lights cannot be mapped into a
lighting model without that support.

      The method described allows a graphics adapter to provide
optimum support for multiple graphical APIs with a minimal loss of
performance or...