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using Manic Miner and Jet Set Willy game engines
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Message: 7196
Author: ian.rushforth
Date: 23/04/2018
Subject: Re: wraparound / mm
[Second attempt after first message disappeared?]
I wrote:
>> Instead, when Willy is falling off the bottom of a Manic Miner cavern, the lower part of his sprite is drawn at
>> the top of the cavern (although in the first time-frame, his lower half may not be visible if the Air INK
>> and PAPER settings match).
> To clarify something arising from that latter point: in the first time-frame, an attribute value corresponding to
> Willy's white INK OR'd with the BRIGHT/PAPER settings of the background is written to the primary attribute > buffer for the cells in the top two cell-rows through which Willy is falling whilst he is straddling the boundary
> between the bottom and top of the cavern.
...but all the colour-attributes that are visible on the physical screen are copied during each time-frame from the secondary attribute buffer, which is itself a snapshot of the primary attribute buffer at the beginning of the current pass through the Main Loop. Hence the time delay of a single-time frame before the lower half of Willy's sprite becomes visible.
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