Conversion Capers: Mayhem in Monsterland

[Codetapper]

Time to resurrect this idea and see how the coders in here would approach converting this famous C64 game.

First up, [ Show youtube player ] to familiarise yourself with the game and all the tricks.

At first glance (level 1), it seems a trivial job, probably a 16 colour screen (as it only scrolls horizontally) but there are a number of issues if you dig deeper or know the game well:

1. The screen can [ Show youtube player ], I'm not sure how many pixels but at least 16 in one frame (eg. 11:41)
2. There's a [ Show youtube player ] on level 1 that would seem perfect for a palette trick (eg. 6:00)
3. There's parallax tricks (with tile animation) [ Show youtube player ] the [ Show youtube player ] (eg. 9:50 and 25:42)
4. Some sections of the game have a *lot* of rotating stars in the background. As you collect them, they disappear obviously. Again, tile animation tricks on the C64.
5. On some levels, [ Show youtube player ] (eg. 30:50)
6. There's a [ Show youtube player ] (at 47:22) that scrolls onto the screen.

Obviously with only 16 colours on the C64, it's not at all difficult to simply draw the entire screen and have it look identical in 4 bitplanes, but to do everything at 50Hz you would have to have some tricks. Dual playfield would make a few things much easier, but sacrifice colours. If enemies were drawn in dual playfield, you would be severely restrict their palette. Could you make the game look good enough?

So over to you, what screenmode, what would you use sprites for etc etc...

[phx]

Originally Posted by Codetapper

First up, [ Show youtube player ] to familiarise yourself with the game and all the tricks.

A technically very impressive game. I didn't notice most C64 games since 1987, after I switched to Amiga.

At first glance (level 1), it seems a trivial job, probably a 16 colour screen (as it only scrolls horizontally) but there are a number of issues if you dig deeper

Agreed. The first level seems trivial. No parallax, no foreground tiles. A simple horizontal scroller. That's a surprising decision, as I would try to show most of the effects very early to keep the player attracted to the game.

The scrolling title screen with the big letters in front are already challenging on the Amiga. There are not enough sprites for it. Drawing with the blitter might be too expensive. Double playfield - too few colours.

The screen can [ Show youtube player ], I'm not sure how many pixels but at least 16 in one frame (eg. 11:41)

Ok. That means you have to be able to draw a complete new column each frame. That's doable (e.g. twelve 16x16 tiles), but annoying, as you would like to save some time here. Maybe you can stop tile animations, and even some monster animations, during fast scrolling, as nobody will notice it.

A problem with porting from the C64 is also that tiles are usually 8x8 pixel based. You would probably have to redesign everything on a 16x16 or 16x8 base.

There's parallax tricks (with tile animation) [ Show youtube player ] the [ Show youtube player ] (eg. 9:50 and 25:42)

Easy to do on the C64, as you will just modify the bitmap of a single character. On the Amiga I probably wouldn't bother much. A trick with repeating sprites may be possible, but also takes a lot of time. I would prefer a static copper background.

Some sections of the game have a *lot* of rotating stars in the background. As you collect them, they disappear obviously. Again, tile animation tricks on the C64.

I have never seen too many objects moving during the game. So there might be enough time to update a dozend of stars. When there are too many we get a problem, of course. The last option would always be to drop the frame rate to 25 fps.

On some levels, [ Show youtube player ] (eg. 30:50)

All those foreground tiles need to be redrawn each frame. In Sqrxz3 I improved my foreground tiles algorithm, so that only those tiles will be redrawn which have objects (sprites) behind. This could save some time.

There's a [ Show youtube player ] (at 47:22) that scrolls onto the screen.

Hm. Your timecode seems to be 1:30 behind mine. But I found it.
It's a really wide waterfall. I have no idea here. Redrawing the whole screen is certainly no option. Maybe sprites, as the pattern is repetitive?

Dual playfield would make a few things much easier, but sacrifice colours. If enemies were drawn in dual playfield, you would be severely restrict their palette. Could you make the game look good enough?

Not in dual playfield. I don't like this mode at all.

So over to you, what screenmode,

I like 32-colour games. But in this case I would choose 16 colours, as it is sufficient and gives us some extra cycles for the heavy blitting-tasks.

what would you use sprites for etc etc...

The scores at the bottom have just a singl colour. Definitely a case for sprites (maybe just one or two sprites).
Otherwise I would use sprites for the effects when you jump onto a monster and some fragments are flying away.
Maybe the waterfall..?

[jimmy2x2x]

Great topic!

I would do the waterfall effect with color cycling, reserving, say, 5 colors and dont use them around the waterfall area, switch the cycling on and off around the waterfall. Once away from waterfall, 5 colours set to normal palette use.

The rotating pickup stars I would do with 1 bitplane animations, just write them directly to the screen each animation frame, (the other bitplanes would be clear). If you design the star animation system to only update 1 or 2 tiles per frame, you could have a decent amount of stars without spending too much processing time, once collected the animation could change to a dissolve animation without extra cost.

[Lonewolf10]

Originally Posted by Codetapper

1. The screen can [ Show youtube player ], I'm not sure how many pixels but at least 16 in one frame (eg. 11:41)

I don't see that as an issue. The levels don't seem to be very big (I only watch the first 15 minutes of the longplay) - perhaps 10 screens wide, so have the entire level drawn during the level intro? (8K * 4 bitplanes * 10 = 320K). It would eat up memory, but would make fast scrolling a non-issue.

Originally Posted by Codetapper

2. There's a [ Show youtube player ] on level 1 that would seem perfect for a palette trick (eg. 6:00)

Agreed. Though notice that there are some background objects drawn in black that only visible as silhouettes when the lightning flashes. This would use 2 colours of the 16 (I'm going for 4 bitplane, single playfield).

Originally Posted by Codetapper

3. There's parallax tricks (with tile animation) [ Show youtube player ] the [ Show youtube player ] (eg. 9:50 and 25:42)

The majority of the parallax is done during the level intro's (looks like 3 layers of parallax to me), with the occasional trick in-game. From what I saw, I doubt anyone would notice it if they were removed as you can't hang about in this game - there is a time limit for each level.

Originally Posted by Codetapper

4. Some sections of the game have a *lot* of rotating stars in the background. As you collect them, they disappear obviously. Again, tile animation tricks on the C64.

One area I saw must've had about 20 of them. Surely have them as animated tiles, updating a few of them each frame?

Originally Posted by Codetapper

5. On some levels, [ Show youtube player ] (eg. 30:50)

Didn't see that far into the video, but if using a single playfield I guess you'd just have a carefully drawn area to ensure the sprite went behind the first few bitplanes? (probably bitplanes 0 and 1)

Originally Posted by Codetapper

6. There's a [ Show youtube player ] (at 47:22) that scrolls onto the screen.

The simplest option (as already mentioned) would be to cycle 2 or 3 colours to make it look like the water was moving. Perhaps combine that with strategic changing of some tiles to enhance the look of the water flowing?



Enemies and the main character appear to be 16x16 pixels in size, so a single sprite for each one. For the bigger enemies, I'd use 3 sprites (they don't appear to be wide enough to require 4) for them.

[Galahad/FLT]

Awesome looking little game. Basically it entirely depends if youre intention is a 1:1 conversion or you intend to amiga-ise it.

that title screen you could get away with making it 32 colours and judicious use of the pallete, thus moving the bitplanes for tha background and not affecting the logo stuff.

if you were to do it Amiga style graphics, then youve got some probs.

fucking awesome looking little game so late in the c64's life

[Codetapper]

Thanks for your comments guys, I have done a little reading in the "diary of a game" section in Commodore Format and early on they mentioned it was 8 pixels/frame scrolling not 16. Unless they increased it later, that might be the limit.

Something I read also suggests the stars were changed to sprites later in development (as it was using up too many characters). That means they avoided lots of enemies in those areas and had groups of stars done with sprites (as the C64 has a physical limit of 8 across, and Mayhem takes up 2 at all times).

Almost all sprites in the game are standard C64 dimensions of 24 pixels wide x 21 high. And many are doubled vertically and/or horizontally.

The game arranges 8x8 tiles into blocks of 32x32 pixels, and a map is 256 blocks wide (so approximately 25 screens wide) but there are vertical strips of control codes in the map which presumably trigger things like palette/music/enemy boss changes etc.

And yes, these guys (Apex) were pretty much the best in the business in regards to perfectionism and technical tricks!

[Retro1234]

Just for fun I put a scrolling Demo in the Zone the Joystick controlls the direction and speed

Just for fun I might add a Sprites/hero -might not see if anyone else picks its up- I think title screen can be dual playfield - tile set is only about 9 colours

[Codetapper]

Where did you get all the levels from? There's an app someone wrote (mayhemeditorv2) but it doesn't work properly on my PC, presumably some libraries/dlls missing.

[Raislin77it]

Originally Posted by Codetapper

Where did you get all the levels from? There's an app someone wrote (mayhemeditorv2) but it doesn't work properly on my PC, presumably some libraries/dlls missing.

CharPad183 has the map files in the example folder

http://csdb.dk/release/?id=101863

[hansel75]

If i remember correctly Mayhem used some colour tricks on the C64 to fake more than 16 colours.

If you look closely at Mayhem you will see colours used that the C64 never had and it's very clever, it appears to be some kind of dithering or alternating colours trick!

So an Amiga conversion would need to use more then 16 colours to reproduce the full range of colours the C64 had ingame, or use some kind of colour hack like on the C64.

If you look here- http://www.psytronik.net/main/index....e-64&Itemid=57
It says one of the features of the game is-> Non-Standard C64 Colours!

[ajk]

The most known trick was to use different colours on alternate lines, which then got mixed in the output due to how the PAL signal is decoded. So you could get quite a few shades in between. Doesn't work the same way with NTSC though.

Also this may or may not be implemented accurately in various emulators (in the first post you can see a clear horizontal line pattern for example, those are probably intended to be mixed if it were viewed on a TV).

[hansel75]

Apparently the Wii VC version of Mayhem is not very accurate compared to a real C64, colours are wrong etc-

[ Show youtube player ]

[alkis]

Originally Posted by Boo Boo

Just for fun I put a scrolling Demo in the Zone the Joystick controlls the direction and speed

Just for fun I might add a Sprites/hero -might not see if anyone else picks its up- I think title screen can be dual playfield - tile set is only about 9 colours

Is that written in AMOS? (cause of the amos.library in libs: )

[Retro1234]

Originally Posted by Codetapper

Where did you get all the levels from? There's an app someone wrote (mayhemeditorv2) but it doesn't work properly on my PC, presumably some libraries/dlls missing.

Originally Posted by Raislin77it

CharPad183 has the map files in the example folder

http://csdb.dk/release/?id=101863

Yep anyone got any sprites?

Originally Posted by alkis

Is that written in AMOS? (cause of the amos.library in libs: )

Yep

[nobody]

16 colors can do this game nicely as long as you use a sophisticated palette like dawnbringers 16. Look in the example that this game uses this palette (yes it is the same 16 colors all around).

[Codetapper]

Originally Posted by Boo Boo

Yep anyone got any sprites?

You can throw these frames into the demo if you want to

[Solid Snake]

The closest you'll get to Sonic/Mario on the C64...O.K there was Great Giana Sisters, but Mayhem In Monsterland had bi-directional scrolling..

Definately one of the best C64 games. Even when many developers had abandoned the C64, the Rowland Bros (John & Steve) continued to push the humble 64 to the limits. No one knew the bread box better than them. I continually supported the C64 and even purchased the disc version (which I still own) of the game from Apex Computer Productions back in 1993...

Most notably remembered for the amazing Creatures games which made the 64 do things nobody could have imagined. The Rowlands designed, coded and composed everything themselves to give the player the best experience ever! You got your money's worth when you bought their games.

Mayhem In Monsterland did appear a few years ago for mobile phones, but it would be a pleasure to play the game again on the Amiga.

Mayhem was a cool 64 mascot....it's a shame the dwindling 64 market deprived the 64 community of a sequel

[john1979]

Mayhem and Creatures use VSP scrolling trick. Which causes some C64s in the wild to crash. But VSP saves raster time in scrolling and is very useful for this kind of game.

I don't think the gameplay was particularly that great in Mayhem, but in Creatures I thought it was perfect. Very challenging game and superb level design.

I am surprised after reading the techincal discussions on this thread that an Amiga remake might have to leave out or tone down some of the effects. The C64 trumping the Amiga? I am impressed.

[phx]

Originally Posted by Codetapper

it was 8 pixels/frame scrolling not 16. Unless they increased it later, that might be the limit.
...
The game arranges 8x8 tiles into blocks of 32x32 pixels,

That's good. So we can easily do 32x32 tiles on the Amiga, which is Blitter-friendly.
With a maximum of 8 pixels/frame we only need to update six 32x32 tiles in the border every four frames. When using double-buffering that would be three 32x32 tiles per frame. Then scrolling is no longer an issue.

and a map is 256 blocks wide (so approximately 25 screens wide)

So we definitely need a tile-scroller and cannot keep the whole map in Chip RAM, as Lonewolf suggested.

[chb]

Great Topic! Mayhem is for sure one of the technically most impressive games on the C64.

Just some ideas:

• The C64 screen mode is using a 16-color palette, but the color restrictions are very different from a 16-color bitmap on the amiga. You can find some nice information here: http://dustlayer.com/vic-ii/2013/4/2...r-by-the-dozen . Mayhem is using character mode, which means 3 global colors for all chars + 1 per char from the colors 8-15 (or only background + individual color in hires) .I do not think any level in Mayhem uses more than eight colors for the chars. definitely the titlescreen background has only 8, so dual playfield + copper for the foreground would do the trick easily here IMHO.
• Mayhem uses PAL blending to generate more colors, which is due to the nature of the PAL color encoding - the color signals from odd and even lines get mixed together, giving a theoretical max of afaik 136 colors. So on a TV set, this effect needs no additional effort also on the Amiga, but it would not work on an RGB monitor. Depending on how Mayhem uses the effect, it could be achieved by either simply using another palette, some copper color changes or not at all (which I doubt is the case).
• The parallax is char based, as far as I can see the pattern is always 16 pixel wide and high, so one could use repeating sprites or an additional bitplane with the pattern (full screen width, 16pix height, 16x preshifted, repeated by copper manipulation of the bitplaneptr).

Some other apex games where ported to the Amiga (Creatures), interesting why not Mayhem.