[TUHS] TeX and groff (was: roff(7))

[Douglas McIlroy]

> If I can be so bold as to offer an interpretation: Doug's approximations
> treat ellipses as mathematical objects and algorithmically determine what
> pixels are closest to points on the infinitesimally-thin curves, while
> Knuth's (or one his students') method acknowledges that the curve has a
> width defined by the nib

Just so.

> I find it impossible that neither Knuth nor Hobby were unaware of McIlroy's
> work and vice-versa; of course he would have known about and examined troff
> just as the Bell Labs folks knew about TeX.

We were generally aware of each other's work. My papers on drawing
lines, circles, and ellipses on rasters, though, were barely connected
to troff. Troff did not contain any drawing algorithms. That work was
relegated to the rendering programs that interpreted ditroff output.
Thus publication-quality rendering with support for thick lines was
outsourced to Adobe and Mergenthaler.

Various PostScript or ditroff postprocessors for screen-based
terminals were written in house. These programs paid little or no
attention to fonts and line widths. But the blit renderers made a
tenuous connection between my ellipse algorithm and troff, since my
work on the topic was stimulated by Rob's need for an ellipse
generator.

Doug