What is the basic idea behind parallax scrolling?. Is it hard to program?

The basic idea to me is that there are multiple levels of background images scrolling at variating speeds; eg the last layer moves the slowest as it's the furthest away, while first layer from the player moves the fastest as it's closest to the player.

I'm only setting my first few footsteps into assembly programming myself at the moment, and I think that Lasse Öörni has the most relevant document of what I've seen so far:

http://www.student.oulu.fi/~lo...scroll.htm

Hmm.. I don't think that rant touches parallax scrolling at all..

I've understood parallax scrolling to be when a layer moves in front of another at higher speed, like in 'Parallax', where in the background there's a slow moving tile pattern. Uridium also has a sort of (though very simple) parallax with the stationary stars behind the scrolling screen.

It's about manipulating the charset so that the stationary/slower moving back layer moves into the opposite direction than the front layer. For a simple repeating pattern this is easy to do, and not even so time-consuming.

But for the trick that Hawkeye/Flimbo's Quest (plus the countless clones released by CP Verlag ) use, there needs to be multiple (4) charsets stored into memory, where in each the back layer chars are in different state of rotation. This involves a certain strategy in drawing the background patterns: as a certain char rotates, another char comes into it, which must be always the same in the BG... (yeah, not very well explained)

The scrollroutine then needs to move the whole screen and repaint the back layer as appropriate, so it appears to either stay stationary or scroll slower as expected. (requires doublebuffering)

Never tried that myself, what I wrote now was based on an article Jukka Tapanimäki had in the finnish mag C=Lehti, about the Hawkeye scrolling. But I guess it's not the easiest thing on this planet..

You can also use interupts to set the built-in screen scrolling routines at different speeds. Shame i can't remember how to do that in practise......my memory has faded.

:oops:

http://www.atariage.com/forums...t=parallax


my 2 cents in parallax...

the basic concept is the same...

http://www.lemon64.com/forum/viewtopic.php?t=2922

My 0.5 cents in parallax ...

Jetboot Jack wrote:

One question, why replicate the C64 -- why not create unique software that the C64 could not do anyway -- rather than try and recreate another machine's glories...

<SARCASM>
WHAT?!? Unique software on Atari that the C64 could not do ??? C'mon dudez! Face reality. C64 RULEZ !!!
</SARCASM>

if i would known your tutorial i had not to invent the wheel twice...

hve

Would you say a scrolltext in a demo/intro controllable both ways at different speeds is Parallax?
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If there is a stationary or slower scrolling background behind the text, then it's parallax. Otherwise not.

Parallax scrolling is a nifty 2-D way to cheat perspective...basically that's its main use..hence scrolling backgrounds at various speeds much like real life.
That's a classical animator's trick and have been around for decades before the commodore ever got made.
Programming it using interrupts shouldn't be overly difficult and yeilds good results for that bland static background you're just dying to fill in.

So say the screen is split in 4 with different speed scrolling, and there are no, for example, sprite overlays, is that *not* parallax?

IE:

----------------
4x scroll
-----------------
3x scroll
-----------------
2x scroll
-----------------
1x scroll
-----------------

I knew parallax meant something moving over a static (or different speed) background (or vice versa), but I also thought this type of split scrolling, could be described as parallax, even without any different speed overlays (sprites) on the top of the scrolling (text) portion. I think the method I'm describing is used in StarRay... (amongst others)
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i would see this as paralax scrolling, too as f.e. this technique is used in games like shadow of the beast... i remember that this "paralax" buzz word i heard 1st time from my amiga/atari ST times... and many games used this technique to create a kind of depth on "plain" 2d screen... if you define paralax scrolling just by moving different layers with different speed than these games are not paralaxing?

check out on amiga/ST:

- enchanted land
- shadow of the beast
- xenon 1+2

hve