Graphics capabilities and home conversions.

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joefish
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Graphics capabilities and home conversions.

Post by joefish » Wed May 06, 2009 4:32 pm

Being a techy geek, when I read machine descriptions in Retro Gamer I'm always a bit disappointed by the inconsistency of the machine specs - particularly the graphics capabilities. Could these be stated in a more consistent manner, such as number of colours, palettes, RAM available, etc? As they're presented, you can't really compare one machine to another.

I'd love to see a piece on the different capabilities of the different 8-bit machines, and how this affected the various game conversions. Mainly I'd like to see a bit more detail on what each machine could do graphically, but I'd also like to see a more in-depth look at different game conversions, as the small summary box-outs don't really do them justice.

I used to rile at Spectrum conversions that ported over low-resolution/high-colour graphics from other 8-bits, but I had no idea how much Amstrad users were suffering from poor Speccy four-colour conversions. The MSX could also do better than a Spectrum, but the single-address way of accessing the dedicated video RAM slowed everything down and made smooth scrolling near impossible.

For example, Alien 8 on an Amstrad is in 4-colour mode, but the sprites are only in two colours (red and yellow) on a black background. Why? It's not the mode, because there's white on the score table at the bottom of the screen. Well, I'm only guessing, but maybe because the sprites are stored with two bits per pixel. On the Speccy, that's one bit for a mask and one for the graphic. On the Amstrad, the two bits give four possibles - red, yellow, transparent, black. So you couldn't have red, yellow, white, black and transparent, as that would need another bit and all the graphics data would be 50% larger.

What about Head over Heels? That has three colours in game? Well, only on the backdrop to each room. All the moving sprites in any one room are only in two colours. Okay, I realise this sounds ridiculously geeky to a lot of people, but there are reasons for some of the oddities. Maybe a better writer could make a more accessible piece out of it.

So have a look at the recent Mister Heli re-review - why does the Spectrum version have 2-pixel wide vertical lines in the graphics? And why does the Amstrad version have a thicker black border than it should? Well, again, only a guess, but could they have designed the graphics for the Amstrad's 16 colour fat pixels, but the screen layouts for the Spectrums's 256x192 pixel screen? So then Spectrum users have to put up with fat pixel graphics with thick vertical lines (and a bit of checkerboard stippling instead of colours), and Amstrad users have to put up with the smaller screen layout. Both get exactly the same pointless scoreboard graphic in the top 1/3 of the screen, to save on time spent redrawing the graphics, and presumably both get the same Z80 core code. But the C64 version looks completely different, as it was done entirely separately.

The less said about 'Leviathan', the better.

Or how about Space Harrier? The C64 version used the character-based mode, so the graphics were fast and colourful but blocky and roughly masked. The Spectrum had smoother scaling, masked graphics, but clearly in only one colour. And the Amstrad version drew everything in vectors because it just couldn't redraw large graphics fast enough.

But there's also another obscure feature to look out for on all conversions of Space Harrier, whilst I'm talking conversions. The game could be quite vicious on new players, particularly at the higher cost someone had paid to play in the tilting cockpit. So there was a DIP switch on the original arcade machine that let you get one minute of free play at the start of every new game. You could die as many times as you liked in that one minute (though dying wasted precious seconds) before your lives started counting down. If you didn't die, it was just about long enough to reach the first dragon. But this was rarely switched on on machines installed in UK arcades (and presumably Japanese ones too), but was more common in the US. So conversions done in the UK and Japan (Spectrum, Amstrad, Megadrive) don't have this feature, but conversions done in the US (C64, GBA) do have it, as that's what the programmers were used to.

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Re: Graphics capabilities and home conversions.

Post by TMR » Wed May 06, 2009 6:08 pm

joefish wrote:I'd love to see a piece on the different capabilities of the different 8-bit machines, and how this affected the various game conversions. Mainly I'd like to see a bit more detail on what each machine could do graphically, but I'd also like to see a more in-depth look at different game conversions, as the small summary box-outs don't really do them justice.
Without wanting to sound immodest, i'm probably one of the better suited bunnies to write a piece like that... but i'd never actually pitch the idea because i honestly don't think the majority of readers would enjoy reading it; judging from the feedback we've had from the more technical discussions on this message board, there aren't many people who want to know what is going on "under the hood".
joefish wrote:So conversions done in the UK and Japan (Spectrum, Amstrad, Megadrive) don't have this feature, but conversions done in the US (C64, GBA) do have it, as that's what the programmers were used to.
The C64 version of Space Harrier wasn't written in the US, it was done in the UK by Chris Butler for Elite.

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Re: Graphics capabilities and home conversions.

Post by Antiriad2097 » Wed May 06, 2009 6:25 pm

joefish wrote:Being a techy geek, when I read machine descriptions in Retro Gamer I'm always a bit disappointed by the inconsistency of the machine specs - particularly the graphics capabilities. Could these be stated in a more consistent manner, such as number of colours, palettes, RAM available, etc? As they're presented, you can't really compare one machine to another.
You'd prbably enjoy this book:
http://www.amazon.com/Encyclopedia-Game ... 3000153594

Its pretty much designed for comparison of systems.
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Re: Graphics capabilities and home conversions.

Post by joefish » Wed May 06, 2009 7:19 pm

TMR wrote:The C64 version of Space Harrier wasn't written in the US, it was done in the UK by Chris Butler for Elite.
Oh, OK, I thought they'd actually bought that one in. To be honest I haven't looked at that version since way back when when it came out, but I seemed to remember wondering why it had that countdown (I'm not imagining that too, am I?). It wasn't until I saw it pop up again on my GameBoy Micro version that I started to dig to see where it came from.

Shame there's not much interest. I realise I want the really geeky stuff, but the challenge is there now to make this stuff accessible! (And then to take the flack for not being technical enough, naturally).

And I'd just figured out how R-Type does its scrolling on the Spectrum, too. But that's another amusing one to look at on different conversions. the Amstrad uses the Spectrum graphics but in fewer colours. The C64 has a funny thing where if you don't shoot down the baddies as you enter the first tunnel, you can see them all clustering in three little groups, not daring to cross the sprite multiplexing boundary - also why there's no rotating gauntlet there either. I quite like all the little tells that give away how the program works, even without hacking into the code.

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Re: Graphics capabilities and home conversions.

Post by Fred83 » Wed May 06, 2009 7:34 pm

i remember reading one retro inspection about one spectrum model,the reasons that the colors where kept simple was due if there was so many on the screen the colors tended to bleed on the screen

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Re: Graphics capabilities and home conversions.

Post by woody.cool » Thu May 07, 2009 2:27 am

Fred83 wrote:i remember reading one retro inspection about one spectrum model,the reasons that the colors where kept simple was due if there was so many on the screen the colors tended to bleed on the screen
You played on a Spectrum?
Colour clash (or colour bleed) is common across all models, and quite a few games.
Some say it adds a bit of charm to the Speccy, some just say it's what make it look so awful.
I sit on the fence with that argument though.

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Re: Graphics capabilities and home conversions.

Post by Antiriad2097 » Thu May 07, 2009 3:19 am

Or, more accurately, you can only have two colours per character block.

The Speccy screen is made of a grid of 8x8 pixel squares.

Each of those squares can have a background colour and a foreground colour. 2. That's it. If any other colour of object enters a given square, either the whole square has to change its foreground/background colour, or the object changes its colours to match the existing square.

Try playing some of the Wally Week games for a good example of colour clash at work - you'll see background objects within the player sprite's rectangle change colour as he passes them.

On the upside, it does give a higher resolution than some of the more colour capable systems of the time, so the objects you do get tend to be quite detailed.
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Re: Graphics capabilities and home conversions.

Post by Seadog74 » Thu May 07, 2009 7:08 am

The topic would be interesting to see which was the best for what etc. Whatever machine we owned or still own had their good points despite the 'playground' arguments.

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Re: Graphics capabilities and home conversions.

Post by avant » Thu May 07, 2009 10:12 am

I'd be really interested in reading an article about this, if it's well written then it won't be "too techy".

From a different angle on this type of topic I recommend checking out this book: http://mitpress.mit.edu/catalog/item/de ... &tid=11696 it shows how games designers got round gameplay and technical issues on the atari 2600. hopefully more to come.

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Re: Graphics capabilities and home conversions.

Post by Matt_B » Thu May 07, 2009 10:44 am

I'd imagine that it could be something of a difficult read in comparison to most RG articles, but good journalism isn't just about giving the readers what they ask for; they need to be challenged too occasionally. :wink:

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Re: Graphics capabilities and home conversions.

Post by joefish » Thu May 07, 2009 3:21 pm

"To inform as well as to entertain", eh?
I think the hook for this is all those playground arguments about which was better, when you only had one machine yourself so never got a balanced view. Now with a bit of explanation you could understand why there were these differences.

(Although quite a bit would have been down to the hiring of freelance programmers who worked at home in isolation, so any tricks one developed could never be applied to another version).

I never quite understood all the graphics modes of the C64. It's not even clear, poking around on internet sites. I gather it had a hi-res mode like the Spectrum, but 320x200 with any two colours in each 8x8 character space. Then it had a lo-res mode which was 160x200 (fatter pixels) with any 3 colours plus a constant background colour in each 4x8 character space. And it could do these as a bit-mapped screen, or as a character-mapped screen with up to 256 user-defined 8x8 (or 4x8) characters. So I'm guessing Space Harrier used the character-mapped mode as it would be quicker to redraw. Plus it had sprites (though sprites also shared two colours and only had one distinct colour to each sprite) and raster interrupts that meant you could change the settings at various points down the screen.

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Re: Graphics capabilities and home conversions.

Post by TMR » Thu May 07, 2009 3:33 pm

joefish wrote:
TMR wrote:The C64 version of Space Harrier wasn't written in the US, it was done in the UK by Chris Butler for Elite.
Oh, OK, I thought they'd actually bought that one in. To be honest I haven't looked at that version since way back when when it came out, but I seemed to remember wondering why it had that countdown (I'm not imagining that too, am I?).
No, the timer is present on both the Elite and Sega releases (the latter gains stripes on the ground which were possibly based on the Omega Man crack of the PAL release but i don't think anyone's ever asked Chris Butler about that). i vaguely remember playing on a hydraulic Space Harrier cab that Elite had taken along to a show (probably a Personal Computer World show or possibly one of the Commodore shows...) that was modified with a button to trigger the coin mech; presumably it was the unit they were using to base the conversions on and it had the timer mode enabled otherwise half of the people in the queue before me would've not lasted more than a minute!
joefish wrote:Shame there's not much interest. I realise I want the really geeky stuff, but the challenge is there now to make this stuff accessible! (And then to take the flack for not being technical enough, naturally).
The closest i've ever got was when i was asked to contribute a little to the C16 Retroinspection - even then i held back on technical details because it wouldn't have been as generally readable otherwise.
joefish wrote:The C64 has a funny thing where if you don't shoot down the baddies as you enter the first tunnel, you can see them all clustering in three little groups, not daring to cross the sprite multiplexing boundary - also why there's no rotating gauntlet there either.
Because the Spectrum version of R-Type took six months to write, the C64 version was produced in six weeks.

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Re: Graphics capabilities and home conversions.

Post by TMR » Thu May 07, 2009 3:39 pm

joefish wrote:I never quite understood all the graphics modes of the C64. It's not even clear, poking around on internet sites. I gather it had a hi-res mode like the Spectrum, but 320x200 with any two colours in each 8x8 character space.
That's right in bitmap mode yes, the Spectrum can't mix different brightnesses but the C64 could select any two colours for each 8x8 pixel cell. In character mode (the one the machine defaults to on power-up) it's 320x200, one background colour and any from the 16 for each 8x8 pixel character and with Extended Colour Mode enabled again it's 320x200 with four possible background colours and sixteen foreground per 8x8 pixel.
joefish wrote:Then it had a lo-res mode which was 160x200 (fatter pixels) with any 3 colours plus a constant background colour in each 4x8 character space. And it could do these as a bit-mapped screen, or as a character-mapped screen with up to 256 user-defined 8x8 (or 4x8) characters.
Not exactly, 160x200 character mode gets one colour per 4x8 pixel cell and three shared colours (one is the background colour) and the character colour is limited to being from the first eight in the palette; high resolution characters (again using the background colour and a character colour from the first eight) can co-exist with multicolour ones in this mode. 160x200 bitmap mode is as you've described.
joefish wrote:So I'm guessing Space Harrier used the character-mapped mode as it would be quicker to redraw.
Yes, that's right.

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Re: Graphics capabilities and home conversions.

Post by Havantgottaclue » Thu May 07, 2009 3:58 pm

I like all the techy stuff, and I think the issue of how conversions of arcade games in particular differed in order to cope with the differing specifications of the 8-bit machines. That's one of the reasons I'm particularly interested in the Atari 8-bit range, because the graphical capabilities are so restrictive in some ways but so powerful in others.

I'm sure it would be possible to do a two-page spread in the article showing various comparative shots of arcade conversions onto the three major 8-bit platforms, showing how backgrounds/bosses/etc. differed, with a little information on how the technical restrictions of the machines forced the programmers into adopting particular solutions. It could perhaps feature as a sorted of extended Conversion Capers. If the text were to be kept relatively short and to the point, with the focus on visual presentation of the comparison, it might generate some interest.
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Re: Graphics capabilities and home conversions.

Post by joefish » Thu May 07, 2009 7:28 pm

TMR wrote:Because the Spectrum version of R-Type took six months to write, the C64 version was produced in six weeks.
See now, six months, that shows dedication on the part of those Spectrum programmers... :D
But then they still managed to @rse up the master tapes so that everyone who got to Level 8 found they'd just loaded Level 7 again. Should have given the boys a bit longer. Still, it does stand out as the Spectrum's finest moment. (Even if I'd rather play Chronos (48K) on the emulator now that I've got a dozen different better ways to play R-Type...)

But seriously, using sprites and tweaking the graphics mode and palette on the rasters will only get you so far, but like the consoles that followed it limits you to only being able to do certain types of games well. Ironic really that Spectrum R-Type looked so good because it used a character-based method for drawing all the sprites, whereas the C64, which could do this in the hardware, instead relied on its proper sprites and didn't look so hot.

Spectrum games may have resorted to monochrome graphics a lot of the time, but with less screen memory it could do things faster and smoother. I think the CPC464 came off worst as it had the same processor as the Spectrum, but nearly three times as much data to shift to refresh the screen whichever mode you were in. 320x200 in 4 colours is half an Atari ST's screen.

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