DRAWL 70(ID:7045/dra007)

Drawing language 

for DRAW Language 1970

Graphics language, part of the ConComp project at Michigan.
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DRAWL => DRAWL 70   Evolution of
References:
  • Herzog, B. and Fred Shadko "DRAWL 70: A COMPUTER GRAPHICS LANGUAGE" THE UNIVERSITY OF MICHIGAN Technical Report 30 CONCOMP: Research in Conversational Use of Computers F. H. Westervelt, Director ORA Project 07449 August 1970 view details Abstract: The DRAWL language provides a simple means of defining a graphical composition and specifying operations on it. A catalog of parts is kept; any defined item may be re-used any number of times. Changes in viewing angle, scale, absolute location, and projection are easily affected in three dimensions via homogeneous coordinate projective geometry. Graphical output is available on cathode-ray tube-displays, digital-incremental plotters, and on-line computer line-printers and remote printing terminals. Extract: Introduction
    Introduction
    Drafting is a method of representing projections of three-dimensional objects in two dimensions. The DRAWL language is a drafting language that takes the pencil out of the draftsman's hands and gives i+ to the computer. The resulting drawings are easily changed, and more easily stored.
    The DRAWL language relieves the user of tedious, non-creative drafting chores and thus provides him with more time for creative work.
    The basis of this drafting system is that all objects are to be described by straight lines connecting specified points in space. Further, it is assumed that a given object is a set of lines collected in one logical element. Thus, generally, invisible lines connecting line segments are required, as illustrated by the rectangular parallelepiped (Figure 2), where the dotted lines represent the invisible lines. All objects are wire-frame figures; no shading or solidity is considered.
    These line segments are defined by sequentially specifying the starting point, all intermediate points, and the end point. Information specifying the visibility of each segment accompanies these definitions.
    Once a number of objects are so defined they may be associated to become an assembly. Several assemblies and objects may, in turn, be collected into another assembly. Conceptually, assemblies may be nested within assemblies to any depth. Thus objects are defined by points, and assemblies are defined as a collection of objects, or as objects and previously defined assemblies. This hierarchy is illustrated in Figure 3.
    To name and construct, i,e., define, objects and assemblies, the following key words and commands are needed:
    NAMOBJ NAMASM
    POINTS NAME
    INCRPT FINASM
    FINOBJ
    Since each of these instructions is a call on a subroutine, each must be preceded by the word CALL. Their use and purpose are described in the sequel. Means for manipulating geometric elements are described; transformations are defined and carried out by the key word instructions
    CALL NAMTRA
    and
    CALL TRANSF.
    Several other key words are provided for executing drawings and other
    convenient functions The following paragraphs describe the rules associated with these key words and provide illustrative examples.