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using Manic Miner and Jet Set Willy game engines
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Message: 6976
Author: ian.rushforth
Date: 13/12/2016
Subject: Re: Quirky conveyors in MM
I wrote:
>> Incidentally, on the subject of quirky aspects of conveyors, I believe that in Manic Miner, if you attempt to create a cavern with a Conveyor Length Byte value of zero, then you will actually end up with a conveyor that is 256 cells in length! > I should point out that I haven't actually tried that yet; at this stage it's purely a prediction, based on an analysis of the 'Move the conveyor' routine at #9105.
Okay, having tried the above (setting the Conveyor Length at Offset 626 to '00', and the coordinates of the start of the conveyor at Offset 624-25 to somewhere within the cavern layout), it does indeed cause the conveyor animation to be spread across the entire upper or lower half of the playing area (i.e. either the top third or the middle third of the screen).
N.B. If the conveyor's start address is set to somewhere in the middle of the upper half of the screen (as opposed to the first cell, at the top-left corner), then the conveying animation doesn't wrap beyond the bottom-right cell of the upper half of the screen to the top-left cell of the lower half. Rather, it resumes at the top-left of the upper half of the screen.
However, the pixel patterns that are displayed, animating in pixel-rows 0 and 2, are based on the pertinent graphic bytes of the cell which lies at the conveyor's defined start address. If that happens to be an Air cell (or a cell in which pixel rows 0 and 2 are Inkless), then pixel-rows 0 and 2 of the entire half of the screen are wiped clear! (This can occur dynamically, if the Conveyor and Crumbly attributes match, and if Willy stands on the leftmost cell of the Conveyor, clearing its pixels.)
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