[stella] Fastest missile/ball draw

Subject: [stella] Fastest missile/ball draw
From: "Bob Montgomery" <BobM@xxxxxxxxxxx>
Date: Fri, 25 Feb 2005 11:18:19 -0500
The fastest way to draw a missile or ball (of variable height) that I have come up with is this:

lda BallHeight
dcp BallYPosition
sbc BallHeight
sta ENABL		;+14

Is there a faster way?

You can shave a cycle if you restrict your BallHeight to intervals of 4:

lda BallHeight
dcp BallYPosition
sbc #0
sta ENABL		;+13

Where BallHeight = 0, 4, 8, etc.
Similar for other BallHeight values.

And you can shave another cycle by replacing BallHeight by #BALLHEIGHT - but is there a faster way for the general case?



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