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ALS, a new graphics system
Quite a regular
Joined:
2006/12/6 0:11
From Italy
Posts: 663
Recently I've been working on a new graphics engine.

VIDEO PREVIEW #1
VIDEO PREVIEW #2
VIDEO PREVIEW #3


OVERVIEW

"ALS" stands for "AMOS Layers System" (formerly "MLS" = "Multi-Layer System"), as it turns the screens of AMOS Professional ("AMOS" from now on) into layers that can be laid over one another, with complete control of order, colors and trasparency, while keeping them renderable as usual.
It is easy to use, does not require much knowledge of the Amiga graphics hardware, does not require installation or extensions, and comes as a set variables, arrays and procedures written in fully-commented AMOS code - it can be thought of as an AMOS source-level library.


GENERAL FEATURES

· Layers usable as screens and vice versa
· Overlaying of multiple layers
· Overlaying order freely arrangeable
· Per-layer planes height
· Per-layer planes number
· Per-layer double-buffering
· Per-layer vertical positioning
· Per-layer colors
· Per-layer 257-degree opaqueness
· Per-color 257-degree opaqueness
· 24-bit internal colors
· LORES horizontal positioning of layers
· LORES and HIRES display resolutions
· Programmable display window size
· Automatic centering of display window
· Automatic adjustment to chipset type (OCS/ECS/AGA)
· Palettes management
· Banks management
· Layers snapshots

ECS/AGA FEATURES

· More flexible positioning of display window
· Display border blanking
· Selectable video standard (NTSC/PAL)

AGA FEATURES

· Non-EHB 6-plane displays/layers
· 4x planes fetch mode
· 24-bit display colors
· 24-bit palette colors
· SHRES display resolution
· SHRES horizontal positioning of layers

RESTRICTIONS DUE TO HARDWARE

· Maximum number of visible planes / 1-plane layers:
· OCS/ECS, HIRES: 4
· OCS/ECS, LORES: 6
· AGA: 8
· On OCS/ECS, when 6 planes used, display colors 32-63 equal to display colors 0-31 with halved brightness
· On OCS/ECS, 12-bit display colors
· On OCS/ECS, 12-bit palette colors
· On OCS, slightly restricted horizontal positioning of display window
· On OCS, fixed video standard (NTSC/PAL) depending on the hardware
· Same width for all layers
· Same horizontal positioning for all layers

RESTRICTIONS DUE TO AMOS

· Maximum number of in-use/ready-to-use layers: 8
· Maximum number of planes per layer: 6

RESTRICTIONS DUE TO DESIGN

· Most AMOS screen effects not allowed/possible
· Serial port not usable


HOW ALS WAS BORN

In 2003 I wrote a Copper-based screen flipping effect for a developer who was making a game with AMOS. Eventually, the effect was not used (and the game was not made at all), but writing it gave birth to a whole bunch of ideas, which little by little brought to the creation of a small graphics system called XPF (Cross PlayField).
The development however, having started from an effect and having proceeded spontaneously, lacked the necessary rigour that a proper system requires, so I decided to rewrite everything from scratch and created CSS (Custom Screens System). That one turned out to be a clean, feature-rich system. It worked nicely and I even wrote a few tutorials for it.
But it didn't support sprites. While pondering on how to add them, I realized that actually the core design wasn't good enough, and that an alternative one would have allowed sprites and have been more efficient, too. Therefore, I wrote another system: AVS (Advanced Video System). When I was at about 80% of the development... I lost the sources. I can't remember how that happened, but for sure I couldn't recover them, so I remained only with the sources dating back to some days before, when some key additions had not been made yet. I was so angry that I hated the idea of reimplementing what had been lost, and that, coupled with the fact that I was about to move country, marked the end of the project.
The idea of rewriting an old game of mine using CSS - which was good enough for the purpose - kept on lingering in my head through the years. I kind of promised myself I'd do that sometime, as a smaller project between bigger ones. But, at the same time, I could never really accept the idea of using a non-optimal system, so a few times I considered completing AVS... only to drop the idea immediately: I just couldn't bother getting acquainted with that old code, maybe discovering that, after all, I'd do things differently once again.
Although I dedicated myself to many other projects, the ghosts of these systems kept on haunting me. In 2019 I presented CSS to the world with a video preview: it was an attempt between doing justice to the system (and thus hopefully make peace with it) and forcing myself to complete the work by exposing publicly the waste and the shame it represented. Since then, I made a new game (Blastaway), I continued the work on a game and released a preview of it (QUOD INIT EXIT IIo), I released two little updates for another game (MeMO), I prepared an update (still unreleased) for yet another game, I created two other graphics systems and made a demo (THE CURE) with one of them. But the ghosts were still there. Well - as they say - enough is enough and better later than never: the time to get rid of them came and I designed and implemented a new and proper system from the scratch - and so ALS was born.


WHAT'S GOING TO HAPPEN?

ALS is almost complete - only one thing is still missing: unsurprisingly, sprites support*. Even the documentation is in place, so, in theory, it could be released already - yes, the plan is to make it available so that other developers can build games and other cool stuff on top of it. However, I'm not going that route because, firstly, I want to test the system thoroughly and, secondly, because it might be lacking in some department and I haven't realized that yet.
Therefore, I decided to develop one or two mini-games with it before releasing it: that will make for a proper test and give me the chance to make also the dream of pimping up an old game come true.

*Sprites are always left behind for one reason: with this system, it's natural to use all the bitplanes available to have as many layers and colors as possible; as a consequence, all the color registers are set automatically as needed by the layers; since the hardware assigns some of those registers to the sprites according to a very limiting scheme, it's very hard or even impossible to draw and arrange the sprites. The only practical solution is not using all the planes (at most 4 on OCS/ECS and 7 on AGA), but that reduces greatly the power and the beauty of layers, which defies the purpose of having layers in first place.
Anyway, implementing sprites is possible and I do intend to do it (a routine is already in place, actually).


PERFORMANCE

Whenever a color, an alpha value, or the stack of the layers gets changed, it is necessary to recalculate all the colors starting from those relative to the first bitplane of the first layer affected (for example: on AGA, if all the bitplanes are used, layer 2 starts from the 5th bitplane and its alpha gets changed, all the colors from 16 to 255 must be recalculated). That is a CPU-intensive operation that AMOS struggles with, so it must be avoided as much as possible by not using dynamic changes or by precalculating palettes (ALS provides specific procedures for that). To give an idea: the video has been recorded using UAE, but on my Amiga 1200 equipped with a 68030 @ 50 MHz the same demo, compiled, slows down when the HUD layer fades in (the colors from 64 to 255 need to be recalculated).
Other than that, the system is quite lightweight.


WHY AMOS CODE?

Although assembly would make the routines dramatically faster, one amusing and motivational thing for me was precisely using AMOS only. Returning to AMOS and writing everything in such language after many years was fun and, additionally, it's just too cool to say: "Hey, this stuff is made in AMOS!"

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Re: ALS, a new graphics system
Supreme Council
Joined:
2006/11/16 19:25
From Sweden
Posts: 3188
Nice!

_________________
Vacca foeda. Sum, ergo edo

Mr Bobo Cornwater
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Re: ALS, a new graphics system
Amigans Defender
Joined:
2006/12/2 13:27
From Taranto, Italy
Posts: 925
@saimo

fantastic mate. :)
maybe is time to go back to amos..

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i'm really tired...
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Re: ALS, a new graphics system
Quite a regular
Joined:
2006/12/6 0:11
From Italy
Posts: 663
@orgin

Thanks!


@afxgroup

Thanks and LOL!


@all

Update: implementation finished! Now it's time to do some testing and writing the second tutorial.

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Re: ALS, a new graphics system
Quite a regular
Joined:
2008/11/3 12:06
From South France
Posts: 763
nice work on Amos !

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All we have to decide is what to do with the time that is given to us.
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Re: ALS, a new graphics system
Quite a regular
Joined:
2006/12/6 0:11
From Italy
Posts: 663
@AmiDARK

Thank you!


@all

VIDEO PREVIEW #4

The implementation is complete and a new demo program has been written both to test ALS and to provide a practical programming example.

The demo initializes a 2-layer display:
* background layer: 4 planes, with opaque colors, for fixed graphics;
* foreground layer: 2 planes, with (partially) transparent colors, for bobs.
Then, it makes some 3-color ghosts bounce around on the foreground layer while changing cyclically their colors and opaqueness.
The effect could be achieved also without ALS by means of the Set Bob and Palette commands, but:
* all the planes (6) would be double-buffered instead of just the planes for layer 1 (2), thus wasting a lot of memory;
* rendering the bobs would be slightly more demanding (as the rendering code would have to consider 6 planes instead of 2);
* it would not be as easy and efficient to handle colors;
* more in general, it is more comfortable to have separate layers/screens to render to.

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