Re: [stella] Brainstorming: 3D-Corridor

Subject: Re: [stella] Brainstorming: 3D-Corridor
From: Erik Mooney <erik@xxxxxxxxxx>
Date: Mon, 24 Mar 2003 14:27:48 -0500
On Mon, 24 Mar 2003 19:32:42 +0100, you wrote:

>Hi there!
>Assuming your task was to programm a 3D-Corridor that 
>gives you the impression of flying through it, like
>in the old Atari arcade "Tunnel Hunt" for example:
>What would your ideas for realizing this effect on the 
>Atari be?


First, you have to decide on the worst-case scenario - that is, what's the
maximum amount of stuff you're trying to do on one scanline?  I think
you'd have to limit it pretty severely.  Probably three colors at the
most, if you're also trying to draw (but not reposition) the two player

Use the ball for the innermost (smallest) color.  If it's acceptable to
have the innermost and outermost sections be the same color, then it's an
easy task to use the playfield.

If not, then you'll have to get tricky with COLUBK, and probably have to
give up on rewriting the playfield registers and do it all through
manipulating COLUBK.  You'd have to do some pretty tricky
single-cycle-precision delays, and the second-innermost color would have
to always be at least 9 pixels wide (LDA Color1 / LDX Color2 / STA COLUBK
/ STX COLUBK), but since the ball goes up to 8 that should be okay.  Four
colors might be doable this way.

You might even have to write different kernel sections for different
widths, if Thomas can't give you enough single-cycle precision...

This all assumes you aren't resorting to flickering or Interleaved
Chronocolor, in which case it's a pretty simple task to draw two colors on
one frame via the playfield and another two on the next frame.  If the
tunnel is moving at high enough speed, it might not even be noticeable.

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