Re: [stella] single line res

Subject: Re: [stella] single line res
From: Ruffin Bailey <rufbo@xxxxxxxxxxxxx>
Date: Tue, 20 Jun 2000 22:52:14 -0400
Glenn Saunders wrote:
> Could someone explain to me how single line res sprites are generated?  In
> all my readings I've never seen a really good explanation for this.  Maybe
> if Greg Troutman still actively reads the list?

I thought the deal was that if you do have single line res, you
essentially lose a great deal of time for your program to "think"... so
much so that it's hard to write a game that does what most games would
need to do.

When I wrote that still-unfinished demo that created single-line res
screens for a platform game, Eckhard pointed out to me the downside of
updating every scan line.  If I left well enough alone and could deal
with double line resolution, I'd have plenty of time for all the logic I
wanted to perform when drawing the playfield on the fly (I would change
where I pulled the PF data from in ROM on certain scan lines for each

But just for the heck of the challenge, I wanted single line res.  So I
sacrificed PF0 graphics instead (making PF0 always blank) and put my
logic for updating scan lines mid-screen on the fly there (when the gun
was over PF0).  With careful screen reflections, I was only completely
losing the left 15% of the screen.  Even so, getting all the logic in
there was a very tight fit.  I could actually do what I wanted to do
with single line sprite resolution if I made sure each sprite and PF
change occured on even or odd numbered (pick one) lines only, but I
wanted single line res in the PF as well.

The bottom line is that it certainly is possible to have single line
resolution (both sprite and PF) without any problem, but by _not_
updating each line (aka, _not_ using single line resolution) you gain
quite a few processor cycles for your game's logic.  It's tough
squeezing much game out of single line resolution, so most games use
double.  TPS does quite an impressive job with single line only.  In my
mind, the double line res for processor cycles is the trick.  Single
line in plane jane.  But single line doesn't give you enough time for
processing events which the double line res methodolgy/trick solves. 

Iirc, of course.  Sorry for rambling a bit; it is a "school night" so
it's kinda late for me to be awake.  ;^)

Ruffin Bailey

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