Re: [stella] single line kernels and horizontal positi

Subject: Re: [stella] single line kernels and horizontal positi
From: Kurt.Woloch@xxxxxxxxx
Date: Mon, 12 Feb 2001 10:16:32 +0100
Glenn Saunders wrote:

>I was wondering, in single-line kernels and sprites which have different 
>horizontal positions on the same screen, how is horizontal motion typically


>Take a game like Atlantis, for instance.  It only draws one sprite going 
>across the screen on any given scanline, right?   And it enforces vertical 
>separation so that there is time to calculate new horizontal positions 
>between ships.  But other games have more free-form displays which would 
>have objects moving vertically through the "compute scanlines".

Well, judging from where games to the HMOVE blank (indicating sprites are
re-used in that line, approximately), it seems they define a pattern where
every fourth, eighth or more line is one where a sprite re-use CAN or WILL
occur. If an object moves smoothly up and down, you can see the HMOVE blank
jump across those positions, rather than moving smoothly with the object.
This allows for re-using sprites given they don't come too close to each
I think at that point the kernel will decide whether to continue the
existing sprite or start a new one (which involves a computation process,
but DOESN'T display the sprite for a few lines).

With love (and many HMOVE blanks to trigger)
Kurt Woloch

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