Posted: 4/16/2014 4:22 AM
Post subject: How exactly does Luck Manipulation work?
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YushiroGowa
Joined: 5/13/2013
Posts: 180
I know that luck manipulation is used to do things like score perfect hits in RPG's and get the biggest income in gambling games and stuff, but I wanted to know, how is done? I'm assuming there's savestates involved or something???? Please reply. Thanks
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Posted: 4/16/2014 4:31 AM
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Patashu
He/Him
Joined: 10/2/2005
Posts: 4017
Depends on the game. I'll give a few examples of each. -Hardware-based RNG: In Pokemon gen 1 and 2, the RNG is advanced based on how many CPU cycles have elapsed. By changing what buttons you press, even if there is no visible change, every RNG value will be different because the game having to read and think about buttons slightly changes the timing. RNG manipulation in this game consists of pressing different buttons that don't effect the game until you get the result you want. -RNG as stream: In Castlevania: Dawn of Sorrow, the RNG does not advance on its own. Instead, whenever something says 'Yo, I need a random number', the next random number is computed and given to that thing. RNG manipulation in this kind of game consists of looking at the 'stream' of upcoming RNG values, highlighting the ones that you want (for example to get a soul or item drop) and either using more or less RNG values to get that one when you need it (For example, every time Soma grunts, a random number is used to decide what sfx is used, and many enemy behaviours and attacks will use random numbers) -RNG as frame counter: In this kind of game the RNG is advanced once every time a frame elapses. To manipulate RNG in this kind of game, you must arrive earlier or later. A good example is Super Mario Bros 2, where the number of frames that has elapsed since you turned on the game modulo 256 (aka a 'global timer' of 8 bits) determines all 'randomness' such as Birdo deciding to fire or not. Also note that some games have multiple, separate RNGs - for example, one for encounters and one for everything else, or one for graphics and one for attacks.
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Posted: 4/16/2014 12:15 PM
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feos
Site Admin, Skilled player (1236)
Joined: 4/17/2010
Posts: 11274
Location: RU
NES TAS of 2011
http://tasvideos.org/ReverseEngineering.html#RandomNumberGenerators
Warning: When making decisions, I try to collect as much data as possible before actually deciding. I try to abstract away and see the principles behind real world events and people's opinions. I try to generalize them and turn into something clear and reusable. I hate depending on unpredictable and having to make lottery guesses. Any problem can be solved by systems thinking and acting.
Posted: 4/17/2014 3:38 AM
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TheAxeMan
Ambassador, Experienced player (697)
Joined: 7/17/2004
Posts: 985
Location: The FLOATING CASTLE
Sometimes the stream and counter approach can be combined. For example, in Final Fantasy the RNG increments constantly as you order your guys but once you order your last guy it stops and only increments each time it is used. In Ultima 4 the RNG cycles once every frame while walking around and cycles an extra time when used. And then during battle it only cycles when used. The simplest RNGs are counters that step through a preset table of values. A more elegant method is the linear feedback shift register. There are also different ways to use the value from the RNG. Maybe the number determines your damage or maybe you crit if it is over or under some threshold. Or maybe if two of the eight bits are both 1 then you get strength on your levelup. Use a debugger and tracelogger to figure this out.
Posted: 4/17/2014 7:20 AM
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Warp
Banned User, Former player
Joined: 3/10/2004
Posts: 7698
Location: Finland
I'm not so sure the OP was so much interested in how RNG's work as in how you manipulate luck in a TAS. The simplest answer to that would be: Try different things until you get the result you want. Beyond that, it becomes more laborious.