Re: Math/Theory Questions about PostScript-style drawing
Re: Math/Theory Questions about PostScript-style drawing
- Subject: Re: Math/Theory Questions about PostScript-style drawing
- From: "Erik M. Buck" <email@hidden>
- Date: Mon, 17 Sep 2001 17:59:39 -0500
>
Is this really more general than PS-style drawing? The matrices and
>
equations he gives are more-or-less exactly reproduced in the PS
>
Language Reference (Red Book). What are you describing that can't
>
be done in PS?
>
What he is describing is a set of math that was well understood 200 years
ago before Postscript was invented. When he says it is MORE GENERAL he
means that it is useful in more places than JUST Postscript. He does not
mean that Postscript does not use the math. Of course the Postscript manual
uses the same math. The math is universal. It is only silly toy graphics
systems that don't use transform matrices.
By the way, the PHIGs graphics system was specified in 1962 and includes API
for all possible 2D vector operations. PHIGs defined the concept of
"current point", defined the concept of a path, used "right hand" coordinate
system (meaning positive angles are counterclockwise with zero at the x axis
like a protractor and like Postscript), defined the screen origin so that
quadrant I (positive X and positive X) was visible just like Postscript,
defined Postscript style line caps, defined the meaning of line widths (i.e.
widths are transformable just like points), etc. PHIGs define the graphics
primitives that we all know and love: moveto, lineto, arcto, curveto,
stroke, fill, clip, etc. PHIGs also included concepts not present in
Postscript like "viewport" and viewing frustum (sp?).
In short, Postscript is a simple stack based interpreted language dedicated
to providing access to the PHIGs graphics model. Pretty much all of
computer graphics is derived from the original PHIGs. The math used in
computer graphics was well understood hundreds of years ago. There is
nothing new under the sun...