RE: [stella] Confused newbie...

Subject: RE: [stella] Confused newbie...
From: "Lee Fastenau" <stella@xxxxxxxxxxxxxxx>
Date: Fri, 8 Oct 2004 23:55:05 -0500
> >So skipDraw needs to be on every scanline, basically?

It doesn't really _need_ to be on every scanline, but that's how you get the
most vertical resolution on a sprite.  If you execute skipdraw (or some
other vertical sprite positioning routine) on every other line, for example,
you would end up with a "chunkier" sprite with half the vertical resolution.

IMHO, it's the horizontal positioning of sprites that really makes the Atari
2600 so "special."  You can do vertical pixel-perfect positioning with
relative ease because you've got 76 cycles worth of execution time in each
scanline.  In fact, there's usually quite a lot (in Atari 2600 terms) of
time left to do other stuff on the scanline once you've decided whether or
not a sprite is supposed to appear on that scanline at all.  Horizontal
positioning is a different story altogether.  The routine Thomas posted will
give you pixel-perfect positioning horizontally, but at the cost of an
entire scanline.  This really just seems to be the price you pay for
"advanced" horizontal positioning.  However, take a look at how HMPx, HMMx,
HMBL, and HMOVE work.  My first baby steps into the world of "beginner"
sprite positioning only involved those and allowed me to digest the "how" of
sprites in smaller byte-sized (har har) chunks.

There are years worth of incredibly insightful posts in the [stella]
archives.  I had essentially written a tiny proof-of-concept shooting game
before I decided to tackle a real project.  That game was really just a
testing ground for all the material I was digesting from sources like the
archives, 2600 101, and the Stella Programmer's Guide.  And while in
retrospect, the SPG just seems a little lacking, it helped build a solid
foundation of knowledge from which to grow.  Not to mention it's just a fun
read. :)

Don't get discouraged.  Just keep experimenting with code.  You'll get it.
(Heh, seems like just yesterday the rest of you were telling me that.)

(Okay, maybe it _was_ just yesterday.)



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