Re: Supercard

["sicklittlemonkey" <Nick.Westgate@gmail.com>]

Eric Smith wrote:
> "Michael J. Mahon" <mjmahon@aol.com> writes:
> > Actually, I think it would be pretty simple today--but no one
> > has done so AFAIK.
>
> Trevor Blackwell's "Apple ][" screesaver that is distributed as part of
> xscreensaver does it.
>
> http://www.jwz.org/xscreensaver/screenshots/
> http://www.trevorblackwell.com/software.html

I had a look at this out of curiosity, expecting to see the usual
artifacting hacks.

But no, you're right, and thanks a lot for this link! His patch is most
*illuminating*! He emulates a typical NSTC display, but far from
idealizing it, includes all the nasty things that often distorted the
resulting image. Outstanding. It's well commented too, including this
chestnut:

+    /* Now filter them. These are infinite impulse response filters
calculated
+       by the script at
http://www-users.cs.york.ac.uk/~fisher/mkfilter. This is
+       fixed-point integer DSP, son. No place for wimps.

You should be right at home Michael! I'd be interested in your
comments.

This is the kind of stuff that NewRisingSun was doing, and has been
incorporated into various other emulators, but I've never seen it well
documented. Not being a DSP guy (well, I get the basics) the step by
step comments here are very useful. Pity he didn't write the other half
of the emulation! Luckily, we have that already ...

Cheers,
Nick.