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The Holy Grail speedrun skip of Marathon Infinity (ES1->ES3)

Posted: Jul 19th '20, 16:48
by The Man
It’s always, at least in theory, been possible to skip from “Electric Sheep One” to “Electric Sheep Three”. There’s an exit polygon on “ES1” that takes the player to “ES3” (it’s the same polygon that takes the player to “Eat the Path” in “Electric Sheep Three”). However, there’s a door that never opens, so most players who looked at the map file in Forge or Weland concluded that this was probably impossible to get through and just gave up.

Then, in 2018, tbcr broke Eternal. There is a polygon that, until Eternal 1.2, would take the player from any of the first four success dreams to “The Near Side of Everywhere” (the final level of the game)… which was behind a similar door. Thanks to Eternal’s unusual assault rifle physics, it was a little bit easier to clip through this door. But only a little bit: it still requires some extremely technical and precise movement – it’s not just a matter of shooting at the ground and firing. It’s also the sort of insane thing only speedrunners would have attempted. Nonetheless, this skip was removed from Eternal 1.2.

Ever since tbcr demonstrated that skip, I figured it was only a matter of time until Infinity’s Holy Grail would fall. It actually took a bit longer than I expected, but it happened last night, and I was actually on the Discord call when it happened – that’s me at the end, obliviously saying that he needed to record it. (I’d headed off to get some food, and was fortunate to return just in time to see the feat performed live.) What ultimately caused this to fall is the extremely janky fluid physics of the Marathon engine. I can’t begin to explain why this skip works – and if anyone can explain it coherently, it might help make this more consistent to pull off, and it might even help make this skip doable on Total Carnage (currently, the player takes too much damage in the lava to survive on TC) – only that it does. It’s the strangest thing, too, because it looks like it isn’t going to work until it actually does.

This creates another obstacle, though, because pulling this off now requires that the player survive “Poor Yorick” with 2x shields… which, to get a truly optimal time, requires another, possibly even more precise grenade skip to be pulled off without taking damage. Dis/Exy in the Discord, naturally, was able to get three different methods for this consistent almost immediately, but I doubt anyone else has a quarter of their level of understanding of how stair physics in this game work, and I wasn’t able to comprehend their explanations last night (though I might’ve just been tired, as it was past 3 am by this point, and I’ve usually been going to sleep unusually early).

Ultimately, the world record was set twice last night after I went to sleep (ares540 got a 13:54 without the “Poor Yorick” jump, and then tbcr got a 13:22 with it), and it’s liable to be in a state of flux until runners get this tech much more consistent. This seems incredibly imprecise at the moment, but I must mention the dedication of speedrunners in general. Runners of games like Super Mario Bros., Super Metroid, and The Legend of Zelda now routinely pull off frame-precise, sub-pixel-perfect tricks that were once thought to be solely the province of tool-assisted speedruns. Admittedly, there is a bit more consistency when you only have to move in two dimensions, but I suspect this movement is liable to become a lot more consistent as time progresses, especially if we gain a better understanding of why the clip works. (Also, stairs. It might be that I’m just failing to understand some of Dis’ explanation, but I feel like we don’t fully understand how the stair physics work either.)

If someone feels like combing through the source code to find an explanation for this, it might help! I’m pretty sure a lot of it has to do with the immense external velocity the player is able to build up by performing this grenade climb, and some of it has to do with the way the player gets stuck on the polygon vertices. tbcr and ares can probably explain this better than I can, but if you get stuck on certain walls/vertices, you absolutely can’t pull off the clip – doing so completely kills your external velocity, or at least cuts it to a point where you can’t perform the clip and survive. There’s also the completely janky fluid mechanics in this game, which I don’t fully understand either.

To give an idea of how much time this saves, the previous route was sub-15 minutes. An even slightly optimised speedrun with this route will easily be able to pull off a sub-11 time, and sub-10 is probably within sight. In all likelihood, this will eventually shave around four and a half minutes off the game’s completion time. This also means that it is now possible to complete a deathless run of Marathon Infinity in the original engine without saving and quitting. Formerly, the “heartbeat bug” would freeze the game if the player transitioned levels fifteen times without dying in any version of the engine from Marathon 2 to Aleph One 1.2.1, inclusive. (Along with vastly improved mouse support, this is why speedrunners now invariably run on Aleph One 1.3.) However, it is now possible to complete the game with a route containing only fifteen levels:

1. “Ne cede malis”
2. “Rise Robot Rise”
3. “Poor Yorick”
4. “Two for the Price of One”
5. “Electric Sheep One”
6. “Electric Sheep Three”
7. “Eat the Path”
8. “By Committee”
9. “One Thousand Thousand Slimy Things”
10. “A Converted Church in Venice, Italy”
11. “Son of Grendel”
12. “Strange Aeons”
13. “Bagged Again”
14. “You Think You’re Big Time? You’re Gonna Die Big Time!”
15. “Aye Mak Sicur”

As it turns out, the current WR runs add “You’re Wormfood, Dude” in between “Eat the Path” and “By Committee”, because that route is faster. But it’s now possible to complete the game with the route above.

In any case, this is a really exciting time for Marathon speedrunners, since the Infinity any% route just got six levels shorter. If you were thinking of studying the route, now is probably as good a time as you’ll ever find again, since it’s still completely unoptimised and undoubtedly going to be improved quickly. The route overnight just got a lot more technical and precise, though – I would suspect this is a harder feat than a lot of the Total Carnage challenges people pull off, despite not currently being possible on Total Carnage. (Again, if you can help get this grenade clip more precise, maybe that will change – tbcr is sceptical, but given that a lot of other people were in turn sceptical for years that the Kindergarten clip would happen, I’m not willing to make any definitive pronouncements.) I’m looking forward to seeing what follows. I also feel like this has given me a much better understanding of how collaborative an endeavour speedrunning is – although only one person’s name will end up on the record, the route is the result of many people’s refinements and discoveries. I always knew that on an intellectual level, but it’s been pretty inspiring to see happen in real time. Or, as the “Eat the Path” terminal says:
There is only one path and that is the path that you take, but you can take more than one path.

Cross over the cell bars, find a new maze, make the maze from its path, find the cell bars, cross over the bars, find a maze, make the maze from its path, eat the food, eat the path.