Turrican 3 AGA

[Muzza]

I've put a demo of Turrican 3 AGA in the zone - it is not a playable game, only a tech experiment where you can scroll around the first level and see the parallax and enemy sprites. Requires AGA and some Fast RAM. It uses all 8 bitplanes for the display, with 16 colours for the parallax background.

I'm not sure whether I'll actually develop this any further. I was just interested in the technical challenges that would be involved, and it was interfering with my sleep enough that I decided to just try it.

Some random thoughts:

Blitter:
This would be the biggest problem. I'm using all HW Sprites for the parallax, so the player, gunshots and all enemies must be drawn using the blitter. With 8 bitplanes, and some copper work eating into DMA, the blitter is struggling to keep up.
For example, in the section with the large platforms, it will slow down. However I am using the Megadrive sprites here that are 64x84. I notice the original Amiga version reduced these to 64x32, so I could do the same.
Even so... I think it is likely I'd eventually have to reduce the display to 7 bitplanes to make it reliably meet 50hz.

HW Sprites:
I have 6 available when running in 2x fetch mode. These all have to go towards the parallax effect. They need to be 16 colours, so I only have 3 really. I run them in 64 pixel wide mode. Sprite 0/1 is positioned at x=0 and x=256 (SSCAN trick). Sprite 2/3 is positioned at x=128. Sprite 4/5 is multiplexed at x=64 and x=192 using the copper each scanline.
This means the background repeats every 128 pixels across, which is very limited compared to the Megadrive version. Vertically it repeats every 160 pixels - meaning I actually store a 352 pixel high sprite (160+display height).
Normally I'd use SPRxCTL to offset the sprites by 1 pixel, and then store 32 frames of pre-shifted animation. But the RAM requirements would get a bit insane, so I use the CPU to adjust SPRxPOS in the copper list each frame and then only store 4 pre-shifted copies.
Using all the HW Sprites for the background means they can't be used for the player. Having to blit the player each frame is another performance drain. The original Amiga version uses HW Sprites for the player and almost all the players weapon shots too, but of course sacrificed the parallax for those weird looking copper bars.

Original Amiga version:
Clearly the original is technically impressive given what they were working with, and what they were targeting, so respect to the devs. But at the end of the day, it was designed for different hardware and so ends up showing the Amigas weaknesses and not using its strengths.
Some levels go down to four colours in the foreground (almost black and white) to try and preserve the parallax. Contrast to the first level of Turrican 2 with it's beautiful sky gradient, and it looks worse than it's predecessor.
It appears to be single buffered. They go nuts on reusing hardware sprites for all the players gun shots. All blits are crammed in at the end of a frame, and when the action gets too heavy it simply doesn't draw certain things. Leading to flickering sprites.
Parallax, HW Sprites, Blitter are all the same challenges an AGA version would face. Eased a bit by having much more RAM and the larger fetch modes, but then limited again by having more colour depth.

Gameplay:
Well... I prefer T2. Small part of me is tempted to make a T2 feeling game using the T3 assets. Getting rid of the grappling hook for one. But it is probably a pipe dream.

[Pyromania]

Thanks for the hard work investigating and exploring this technical challenge.

[ransom1122]

Very nice

[ Show youtube player ]

[DanyPPC]

I think You made a great work with Turrican 2 AGA, perhaps the best possible AGA conversion in real 256 colors.

[Reido]

This looks amazing! Have a real soft spot for T3. Great work so far, and fingers crossed you find time and the motivation to continue development

[sokolovic]

Isn't the original using dual playfied mode ?
That's magical how they managed to fit this game on 512Kb.

Anyway, thanks for having a look a this game. Considering how much it is impressive on a 512k Amiga, I was always curious to think how an AGA polished version would like.

[Reynolds]

Well, Some levels are truly suffering from lack of colours, so if this would see the light of day, that would be somewhat outstanding for sure. Although if gfx assets could be replaced, that also could help improving the game in the original game too.

Nice work what you did already, hats off!

[viddi]

I think T3 is almost perfect and I also prefer the grittier looks of it.

If I would change something it's the copper pallette of the scrapyard.
Maybe use dark yellow (instead of pink) combined with the shades of gray.

Plus adding the gearwheel animation in the last level.

[alexh]

Thanks for sharing.

Is the limiting factor the CPU bandwidth? ChipRAM bandwidth?

[Muzza]

Originally Posted by alexh

Is the limiting factor the CPU bandwidth? ChipRAM bandwidth?

Limits are everywhere, but if I could pick one thing, having a slightly faster blitter on AGA would solve so many issues.

[Muzza]

I am a little intrigued about this AGA hardware hack.
There is not much documented about it, but it seems to allow 4x bitplane fetch mode, all HW sprites, but loses 1 audio channel. I couldn't get it to work from the descriptions in that link (although I didn't spend too long on it).
Losing 1 audio channel is perhaps not the end of the world when an audio mixer can be used, and using 4x bitplane fetch mode would give a fair few DMA slots back to the blitter.

[TCD]

Originally Posted by Muzza

Gameplay:
Well... I prefer T2. Small part of me is tempted to make a T2 feeling game using the T3 assets. Getting rid of the grappling hook for one. But it is probably a pipe dream.

If it possible that would be amazing I came to terms with the grappling hook, but I still don't like it very much. Using the assets of Turrican 3 and making it play like Turrican 2 would be something I would really appreciate

[sokolovic]

Well that would be another game then. And you probably can forget to call it Turrican because it would be a bit direspectful of Factor 5 work. They won't surely give their approval the same way they did for Turrican 2.

[demoniac]

Very interesting results. I don't like the grappling hook either, but I imagine some level design is based around it and one cannot complete sections without it.

[skan]

Muzza strikes back!

[kremiso]

thanks for investigating also on this ++

maybe a double jump could replace the not great grapple thing
or a jetpack fireboost thing

[Muzza]

Originally Posted by sokolovic

Well that would be another game then. And you probably can forget to call it Turrican because it would be a bit direspectful of Factor 5 work. They won't surely give their approval the same way they did for Turrican 2.

They didn’t give their approval. Just an unofficial indication that they don’t care enough to take legal action.
Look at T2002 to see how people have remixed various Turrican assets from various official games into new games.

[Predseda]

Turrican 3 on Amiga looks terrible in those scrapyard levels, thats true. But also contains Golden Armors

[skan]

Originally Posted by kremiso

thanks for investigating also on this ++

maybe a double jump could replace the not great grapple thing
or a jetpack fireboost thing

Good point!

[lmimmfn]

Looks lovely, just an idea but would using dual playfield but enhancing the foreground colours with some sprites work better? Realise it would be complex to implement based on positioning with the map but it might work due to tiles looking like they have different palettes.