Screen resolution and colour tricks of OCS/ECS games

[Harrison]

Once I do some updates the these forums next month we can start to suggest threads like this, which we can promote to site articles. Things like this really do add some interesting things to the site for sure.

You are also more than welcome to use the blog feature built into this forum to start your own blog about this subject. Would be interesting to see it explored more.

[Khephren]

The only problem with a blog is i'd be afraid it would get lost. And I like post feedback to hear what everyone else has to say.

Brian the lion
Here's an interesting one.

Brian starts off with some techniques we have already seen- 32 colour main screen, copper fade on main screen, 32 colour status bar as a new screen. Adds up to over 100 colours on screen.

brian_the_lion_07.png

Now it gets clever. This section uses a demo scene technique developed by Chaos/Sanity called the '102 register trick'. It uses the copper chip to shrink the scan line. It also appears to change the palette on each line as well.

207_screen9.png

here's a video of it in action:
http://www.youtube.com/watch?v=mZzeA...D56469635FAEB6

ElfMania
Another interesting one is elf mania. In some places featuring over 100 colours. Now you can see a purple copper fade, but take that away and it is still 80 colours. The answer is in the red energy bars and 'Janika' text, as well as in the cyan fade. Again they are well disguised copper bars. Remove those, and the game is 64 colour extra halfbrite. cunning!
elfmania_06.png

Shadow of the beast
Probably the one of the games that pioneered sublte use of some of these techniques. It also uses bobs (blitter objects) or software sprites to you and me, to create the parallax layers. I also has more than the maximum (8) Sprites on screen at once using multiplexing in the code. SotB features one big copper fade, and then a smaller one in the actual score at the top. Has over 100+ colours at some points. One of the costs of heavy use of these techniques is resolution, whether because of processor/Co-processor bandwith, or memory, I don't know. I'm not coder enough to know such arcanery

shadow_of_the_beast_05.png

So far then, whatever trick you use, the main sprites and background tiles remain at regular Amiga colour formats. Pioneer plague seems to be the only one here to go above those limitations.

[Harrison]

Didn't some games combine multiple sprite's to exceed the maximum sprite dimensions and number of colours? Or am I thinking about Megadrive and SNES game tricks? I seem to remember reading they did this with the SNES version of Street Fighter II, which was the best home version. but I'm also sure i read somewhere about some Amiga games using a similar technique.

Regarding demoscene techniques. It was definitely always the demoscene which invented the best hardware coding tricks that we ended up seeing in games. If it wasn't for the demoscene we wouldn't have seen any of the later doom style games. They were told Doom couldn't be made to run on the Amiga due to the graphical hardware differences (Chunky vs Planer) and this made them prove that was wrong and it could be done... The Amiga demoscene was, and still is an amazing thing. I also thought it was such a shame the CD32's Akiko chip was never really explored by many developers. Having the Chunky to Planer conversion in hardware should have provided a lot of possibilities, but did we ever see it utilised? (I know that is a bit off the main topic but it is interesting to me).

[Harrison]

The only problem with a blog is i'd be afraid it would get lost. And I like post feedback to hear what everyone else has to say.

Blogs on here have a comment feature underneath, and new blog entries show in the home page portal and in the right-hand new blog entry listings. But I get what you are saying. A full forum thread like this allows much greater discussion.

The reason I mentioned promoting to an article, is because it is possible to link an article to a discussion thread like this one, so a main article can exist and be updated, whilst the discussion can continue in a thread. This is something I want to explore more and getting working on here soon.

[Khephren]

Ah, I see what you mean about blogs. To be honest, i'm pretty rubbish. I only learnt to inset pictures for this thread I'm on EAB and Amiga.org as well, I never use half the features they offer.

Regarding Sprites/colours:

Yeah, just added sprite multiplexing to the SotB section. To those who don't know, the Amiga (OCS/ECS) can display 8 sprites, in 3 colours, per scan line (16 pixels wide, any in height). It can 'Attatch' sprites to get 4, 16 colour sprites. You can then 'multiplex' the sprites in code to gain more than eight per line. I don't know what the limit is. I guess you could overlay sprites on top of one another...may be I should rip some sprites next ....if I ever get WinUae working again.

After that you have software sprites, less limited in number, colour, and resolution, but needing more bandwith and processor time.

I also love demos, maybe one day i'll do some notes on which Demo groups formed their own games companies, or which members worked on which games. Many of them still do, it's been my privalage to work with a few.

As for Akiko, so under used And really, the A1200 should have had it as well. But then, I also think the A1200 should have ran at full speed out of the box, had fast ram and a HD floppy drive. But them's the breaks!

[Harrison]

There definitely have been a lot of ex demosceners working in the games industry. Their scene releases really showcased what they could do and that alone got a lot of them jobs. IThere are a lot of people who started out with the Amiga, whom are now heavy weights in the games industry as a whole. The Amiga basically "kickstarted" their carriers! (pun intended).

Regarding A1200. Fully agree. If it were not for the A4000 I think more of these features would have been standard. But Commodore had to distance the top end system from the budget end home system. If they had included fast ram, a HD floppy and a HDD as standard there would have been little reason for the A4000 in its vanilla state at its much higher price point (£999 compared to £299).

[burns flipper]

Didn't Brian The Lion feature some sort of Mode7 thing for the intro?

And how did you get all this knowledge? That would be as interesting as the knowledge itself!

[Khephren]

Had an amiga since '88 and just read magazines and kept up with technical discussions on forums, and sometimes with guys iv'e worked with. As for the analysis itself, once you know what to look for, photoshop is your friend!

[Lord Riton]

To those who don't know, the Amiga (OCS/ECS) can display 8 sprites, in 3 colours, per scan line (16 pixels wide, any in height). It can 'Attatch' sprites to get 4, 16 colour sprites. You can then 'multiplex' the sprites in code to gain more than eight per line.

To get more than 8 per line, the copper will have to change the horizontal position of one of the "real" 8 sprites somewhere at each rasterbeam line. This is not only DMA time consuming, but also you then will have problems to move your "doubbled" sprites horizontaly. You won't be able to move them across the vertical line at where the copper changes the sprite position anymore. Same goes with changing the sprites color every scan-line, a normal sprite has up to 4 colors, if you want to change it each scan line you have to use the copper.

After that you have software sprites, less limited in number, colour, and resolution, but needing more bandwith and processor time.

Software sprites do not really exist. I mean, they are not really sprites, but simply blitter objects, "bobs" if you preffer.

I came from the Commodore 64, and seriously, they didn't improve sprites much for the Amiga, i was rather disapointed. While the sprites were really a main core thing in C64 games, they were much less important for the Amiga, because small, with only 4 colors, and still only 8, like on the c64.

I remember the Nintendo 16 bit that was out about that time had up to 128 real hardware sprites, in 16 colors each, up to 64x64 pixels.

---------- Post added at 11:33 ---------- Previous post was at 11:18 ----------

ElfMania
Another interesting one is elf mania. In some places featuring over 100 colours. Now you can see a purple copper fade, but take that away and it is still 80 colours. The answer is in the red energy bars and 'Janika' text, as well as in the cyan fade. Again they are well disguised copper bars. Remove those, and the game is 64 colour extra halfbrite. cunning!
elfmania_06.png

I don't know, maybe you are right, but if you remove the copper bars we see in the back, for me this looks rather like a 16 color picture, eventualy 32, for sure not more