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#61 | |
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Join Date: Apr 2018
Location: UK
Posts: 495
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Quote:
The CPC thing comes up quite a lot. It can scroll and has various ways of doing it both push (which was used back in the day a lot) and real scrolling which was not used until the 90s for whatever reason. |
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#62 | |
Inviyya Dude!
Join Date: Sep 2016
Location: Amiga Island
Posts: 2,807
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Quote:
This is true. I think we are having two different discussions here. One is about hardware registers existing that shove the screen n pixels to the left. The other seems about if that happens in one pixel steps or not. |
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#63 | |
Going nowhere
Join Date: Oct 2001
Location: United Kingdom
Age: 50
Posts: 9,035
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Quote:
Enchanted Land did a slightly more refined version on ST which for some inexplicable reason was duplicated on Amiga. Personally, I have no problem with push scrolling if its not a fast action game |
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#64 | ||
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Join Date: Mar 2018
Location: Hastings, New Zealand
Posts: 2,862
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Quote:
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The Amstrad CPC has hardware scrolling via the 6845 CRTC chip. It is normally limited to 'character' scrolling, which is 8 pixels horizontally in hires (640x200), 4 pixels in medium res (320x200), and 2 pixels in lores (160x200). The scrolling distance is always the same (1 hires character width) so to make it look smooth it has to be scrolled fast. There is a way to get smaller scroll steps by adjusting the width of the horizontal sync pulse, but this only works properly with some monitors. Many CPC games were ported from other platforms with either no hardware scrolling or incompatible hardware, so software scrolling was often used in a reduced screen area. Even worse, some Spectrum ports emulated the Spectrum's 1 bit per pixel graphics in a medium res (4 color) screen using only half the available colors, complete with color cash! This could make the CPC scroll half as fast or worse (not 100x worse though). |
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#65 |
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Join Date: Jul 2015
Location: The Netherlands
Posts: 3,464
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On the topic of ST games, I've seen a bunch of ST games that use smooth vertical scrolling (Paradroid 90 springs to mind). Is this what they call 'Sync Scrolling'?
I've always wondered how that works, as it doesn't seem to be a HW supported feature. |
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#66 | |
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Join Date: Dec 2014
Location: germany
Posts: 449
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Quote:
Not sure about P90, but a quite good explanation can be found here: https://www.atari-forum.com/viewtopi...p=39325#p39325 In short, usually you can only set the STs display address in 256 byte increments, but by switching between 50 Hz and 60 Hz modes in the right places, some ddfstop-like comparisions are disabled and the graphic chip can be tricked into fetching "too much" data, thus ending up on an arbitrary (even) address. So there are some (black) lines at the start of the frame needed to prime the display. |
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#67 |
Inviyya Dude!
Join Date: Sep 2016
Location: Amiga Island
Posts: 2,807
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I have the highest respect for the ST coders, and the shit they have to put up with...
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#68 |
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Location: The Netherlands
Posts: 3,464
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Ah, that's quite interesting, thanks. Always nice to see some proper HW banging going on to utterly confuse the poor built-in chips and get the results you want
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#69 |
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Join Date: Oct 2007
Location: Athens , Greece
Posts: 1,863
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@DanScott
yup, 25/30 |
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#70 |
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Syncscroll on the ST is a demoscene thing, it was the next logical step after the fullscreen technique. Basically, it's all about managing to have different formats of lines at the beginning of the frame, instead of the regular 160 bytes per line in low res, which results in faking a new screen address, hence making the entire screen scroll.
Those tricks rely on perfect beam synchronization, with resolution and screen frequency changes at perfect timings in the frame, many times per scanline. For the fullscreen technique, it means that any code you have has to be cycle constant and precisely integrated in your fullscreen routine each line. The syncscroll technique was used in very few ST games made by demomakers (Enchanted Lands, Lethal Xcess, No Buddies Land, Leavin' Teramis) Paradroid 90 did not use that technique, whatever they used was probably just regular brute force 68000 scrolling with movems. Coding on the ST is actually very fun, it makes you work with constraints and come up with crazy ideas and techniques such as the syncscroll trick. That's probably how Leonard came up recently with the fastest mod player ever on the Amiga, he used a trick similar to what we used to play soundchip tunes on the ST in fullscreen. Last edited by Keops/Equinox; 19 October 2022 at 04:03. |
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#71 | |
Inviyya Dude!
Join Date: Sep 2016
Location: Amiga Island
Posts: 2,807
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Quote:
There is no bad hardware, only challenges to get something great out of it. That said, if i were to create something for the ST, I'd probably go for a switch screen approach like Cybernoid or Exolon. |
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#72 | |
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Location: The Netherlands
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#73 |
68k
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#74 |
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#75 | |
Inviyya Dude!
Join Date: Sep 2016
Location: Amiga Island
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That's how I understand it, anyhow... ![]() |
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#76 |
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Location: Eastbourne
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Yikes. Any push-scrolling conversion of a game designed to have smooth scrolling must instantly be much harder than the original version. Add in diagonally-scrolling blind jumps and it must become borderline unplayable (check out ST Robocod for an example). No wonder most of the best platformers on the ST were vertical scrollers or flip-screen.
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#77 |
Banned
Join Date: Oct 2021
Location: SA
Posts: 283
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btw,
the amstrad cpc was so buggy that even the vertical scrolling is bad I just was testing ikari warriors , the vertical scrolling is horrible, slow and cause partial gfx corruption, the game is colorful but slow and blocky gfx again in this case the zx spectrum version is far better, less colorful but smooth and better resolution Last edited by Marce; 19 October 2022 at 15:57. |
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#78 | |
Banned
Join Date: Oct 2021
Location: SA
Posts: 283
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Quote:
the Amiga version of adams family performs perfect horizontal scrolling just play both versions then u will understand |
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#79 | |
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Location: UK
Posts: 1,908
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Quote:
This is different from something like a beat 'em up which may not scroll until you get to a certain point on the screen and then continuously scroll or even pause to allow a certain number of fights before then continuously scrolling to the next section. So simply - push scrolling is when the screen doesn't scroll continuously and when you get to a certain point, the screen 'pushes' you back as it scrolls a a certain amount in one go. Obviously this is less CPU intensive as scrolling is not happening every frame or loop of the code. The Adams Family is a good example (ST first and then the Amiga is next) [ Show youtube player ] |
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#80 | |
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Join Date: Sep 2004
Location: Brasil
Age: 50
Posts: 181
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Quote:
IW is a typical zx port using software scroll and hidden buffer. For me, the worst thing is the use of a hidden buffer instead of double buffer, wasting even more cpu in the process of drawing the screen; and of course, making visible an annoying tearing when the screen scrolls. If you really want to understand how the cpc hardware scroll works, I will be glad of explaining to you in all detail. And if you want to see cpc games making use of the hardware scroll, you can take a look to games as Prohibition by Infogrames or Skateball by Titus, for example. But it is very important to see those games in a CPC using a CRT, you will not feel smooth by looking them in youtube videos. |
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Thread | Thread Starter | Forum | Replies | Last Post |
9 Lives - smooth scrolling | punkrulesok | support.Games | 14 | 22 November 2018 22:24 |
smooth scrolling.is it possible? | kirk | support.WinUAE | 30 | 01 October 2007 13:57 |
smooth scrolling | sink | support.WinUAE | 3 | 20 July 2007 01:16 |
Smooth scrolling with WinUAE? | Tony Landais | support.WinUAE | 13 | 30 May 2007 03:55 |
Just can't get smooth scrolling | Bobbin | support.WinUAE | 0 | 23 November 2002 00:52 |
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