Porting SOTB to the Falcon

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ggn
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Re: Porting SOTB to the Falcon

Postby ggn » Wed May 15, 2019 5:45 am

dhedberg wrote:Yes it can. Hardware scrolling has nothing to do with the bandwidth. The only restriction is that you have to set the screen address to an even word, so for horizontal scrolling in TrueColor you can't scroll an odd number of pixels per VBL, i.e., 2 pixels per VBL are the minimum.

mikro wrote:
dhedberg wrote:Yes it can. Hardware scrolling has nothing to do with the bandwidth. The only restriction is that you have to set the screen address to an even word, so for horizontal scrolling in TrueColor you can't scroll an odd number of pixels per VBL, i.e., 2 pixels per VBL are the minimum.

Actually, even this can be worked around at no cost -- don't know if he was the first one to discover it but I saw a great trick by Patrice Mandin in his Street Figther demo/port - using the Videl horizontal setting registers to simulate the missing word.


There's another way to do this without fiddling with Videl at all - just have 2 copies of your playfield, one normal and one shifted right by one pixel. When you scroll to an "even" position use the first buffer and when on "odd" just use the second. It burns a bit of ram but hey, no tricks! Also I recall using Patrice's trick, it worked fine on my machine but in Christos' monitor it scrolled the right hand side of the border would flash (or something similar).
is 73 Falcon patched atari games enough ? ^^

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calimero
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Re: Porting SOTB to the Falcon

Postby calimero » Wed May 15, 2019 9:56 am

Can you set video address for each horizontal line on Falcon?
Zarchos use this ability on Archimedes to achieve part of paralax scroll in his demo...

btw Minter's Llama Zap use bitplanes or TC?
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Re: Porting SOTB to the Falcon

Postby joska » Wed May 15, 2019 11:21 am

calimero wrote:Can you set video address for each horizontal line on Falcon?


Interesting question. You can do this on the STE, but I don't know about the Falcon.

calimero wrote:Zarchos use this ability on Archimedes to achieve part of paralax scroll in his demo...


In some of the screens in SOTB almost the entire screen consists of atleast two overlapping playfields. In 16 bit on the Falcon you need to draw most of the screen to achieve this, which is rather difficult since the bandwidth just isn't there. Hardware scrolling would be of limited use in this case. It would probably be much easier to do this in 8 bit mode. If I understand Zarchos correctly he wanted to use 16 bit not because of the extra colours, but to be able to reuse the chunky pixel logic from his Archimedes port.

calimero wrote:btw Minter's Llama Zap use bitplanes or TC?


Looks like he's using a lot of his trademark colour cycling tricks so almost certainly bitplanes.
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