Gem corruption probabilities

Hi,

when corrupting gems with Doryani's Institute, the chances are
25% +/- lvl
25% +/- qual
25% nothing
25% vaal(or nothing - 50% chance total)

1. Assume I rolled + lvl. What are the chances for next roll? Is it

33% +- qual
33% nothig
33% vaal(or nothing - 66% chance total) ?

2. How does the vaal roll works for unvaalable gems? Does it become explicit 50% nothing or is it rolled but no effect? If I roll vaal on first roll, nothing happens, is vaal rollable on the next roll or technically it was rolled so it's
33% +- lvl
33% +- qual
33% nothing?

Thanks in advance,
Xarthac

They give us no odds info so hard to know, since we cant see both rolls.

I've tried to look this up before and found conflicting information. As the above poster says, I don't think the full details are known, or at least not commonly known.

Here is the wiki -

https://www.poewiki.net/wiki/Doryani%27s_Institute#cite_note-1

From this I can think of 3 possible ways it may work.

-Conditional as you have stated. (Case 1)
-Independent 4*4 (Case 2)
-Conditional but with qual/level being able to roll both up and down. (Case 3)

Here is a video of a player explaining how it might work in the conditional case you are suggesting, and giving some associated probabilities.

https://www.youtube.com/watch?v=ql5c2837BNg&ab_channel=animeprincess

I agree with his logic, however I am not certain the premise of conditionality is correct.

One of my reason for thinking it may work differently is that it is possible to get a net zero effect on a gem with a vaal version. You can see this in the annotated video in the wiki for lightning trap, which has a vaal version. It is a 5/10 that becomes a 5/10 corrupted. The only ways I can think this is possible are:

- up/down level or up/down equal qual. (needs to be case 2 or 3)
- rolling no effect twice (needs to be case 2)
- rolling +0 qual and no effect (1,2 or 3 but requires +0qaul outcome)

In all cases there would be only a small deviation in probability's, and it is hard to test on mass without buying a lot of temples or pooling data. I have only run a handful myself so I have very limited insight.

Further information regarding the probabilities I have heard but can not confirm are that all 4 outcomes have equal weight 25%. Level is then split half up half down. Qual is split +/-10 meaning probability of getting 23% qual from a 20% qual gem is 8/20 when qual is rolled.


Some other questions I have that may be able to rule out possibilities:

Has anyone ever rolled down 2 levels on a gem, from 20 to 18? or down more than 10 qual, implying a double independent roll?

Has it ever been possible to roll a 22/20 gem, say around the time of incursion league? Implying max level restriction cap of +1 to natural was added in a subsequent league, and the system might be adapted from the old mechanic.


I can provide the math but it is just theoretical without confirmation of how the system works, without confirmation from GGG, datamining or at least data from a reasonable amount of trials (100 would be a good starting point). In any case it will be fairly similar to the numbers provided in animeprincess's video.

some wiki article are fucked by people that does not know stat or doing controlled experiment

And i have no time to fix it or farm temple to verify....

Here is some players running small sample size of Doryani Institute:

https://www.youtube.com/watch?v=UkVLU5XtrZo&ab_channel=Omisid
https://www.youtube.com/watch?v=SeHhBD5p308&ab_channel=Lolcohol

I haven't heard of double up or down rolls being possible at any level so I'm assuming the outcome is not possible and the sample space of outcomes from rolling a 20/20 is:

{19/10, 19/11, 19/12, 19/13, 19/14, 19/15, 19/16, 19/17, 19/18, 19/19, 19/20, 19/21, 19/22, 19/23, 20/10, 20/11, 20/12, 20/13, 20/14, 20/15, 20/16, 20/17, 20/18, 20/19, 20/20, 20/21, 20/22, 20/23, 21/10, 21/11, 21/12, 21/13, 21/14, 21/15, 21/16, 21/17, 21/18, 21/19, 21/20, 21/21, 21/22, 21/23, 19/20v, 20/10v, 20/11v, 20/12v 20/13v, 20/14v, 20/15v, 20/16v, 20/17v, 20/18v, 20/19v, 20/20v, 20/21v, 20/22v, 20/23v, 21/20v}


As to OP's question, I'm unsure, may be independent, may be conditional, and gems without a vaal variant may or may not have an increase probabilty of rolling desired attributes. Also unsure if +0 qual is possible from a single roll, because it would look identical to a nothing roll, leaning towards no, bit without evidence.

To give some idea of what the difference in probability might be of rolling a 21/23 gem in each case -

Independent: [1/8 (Up level)]* [1/8*8/10 (23 qual)]*2 combinations = 2.50%
Conditional(with up/down possible): [1/8]*[1/7*8/10]*2 combinations = 2.86%

Being able to decipher the difference on such a small variation by statistics would take a large amount of trials, which is difficult in this case because running the trials is gated by acquiring maps and running to the chamber.

Whether the probabilities of the 4 outcomes are all 25% I also don't know, I'm guessing this is based upon peoples knowledge of using vaal orbs?

Looks like there is upto date information on the Doryani institute wiki now. I'm not sure when it was added or if it was there and I was just looking on the Vaal page, but it seems to be more definitive than anything I have speculated in this thread.

https://www.poewiki.net/wiki/Doryani%27s_Institute

It explains the mechanic and the probabilities, I assume they are correct.

I think some of this information that is relevant to single corruption should also be added to the Vaal orb page.

There is some further discussion in this thread, where I was linked the table.

https://www.pathofexile.com/forum/view-thread/3841287