Frankly, it is a really fun concept befitting an arcanist. Seems to be a very potent and interesting feat with one glaring issue. I could seriously see this really holding the game up unless you are confident that you can not only find an answer quickly, but conclude that the numbers you rolled have no possibility of providing the number you are looking for equally fast. Maybe ask if you can try it with the stipulation of that if anyone, including you, ANYONE at your table feels it is taking to long to attempt this, then you may retrain free of charge. With all this in mind, and you feel confident you are capable of doing this expeditiously, GO FOR IT. This could make you one bad mofo, Just don't get to hung up on having your fluff have these mechanical benefits. While it is very cool to have mechanical support for your fluff, this is one that could really slow the game down. If you do try this I sincerely hope you succeed. :)
The problem with these feats is that in the hands of someone who doesn't know what they're doing, they slow the game to a crawl, and in the hands of someone who DOES know what they're doing, they're simply flat power boosts with little actual nuance.
How to know what you're doing with Arithmancy: Pre calculate the digital roots and figure out the DCs for all of your spells. They don't change. Fireball will always be DC 15. Simply boost your spellcraft check to a reliable level, such as with an armillary amulet, and the feat will effectively give you +1 CL to all spells for the cost of a swift action.
How to know what you're doing with Sacred Geometry: Use this calculator. Or this one. If you don't want to, are very good at math, and have practiced using this feat until it's easy for you, you might be able to use it in an actual game without wasting too much of the group's time. Once you get 12 ranks in Knowledge Engineering, it is mathematically impossible for you to make a failing roll. Thus after a certain point, this feat effectively gives you several levels of free metamatic, using metamagic feats you don't even have, for the cost of a full round action. That's extremely powerful.
Here's a chart of success rates for every given spell level and number of ranks in Knowledge Engineering. X axis is ranks, Y axis is spell level.
How to know what you're doing with Calculating Mind: There's no point in taking it. Base Sacred Geometry is reliable enough, and Calculating Mind won't improve your success chance any more.
So playing a mathmagician type character with these feats is cool and flavorful, but just be aware that it might make you ludicrously powerful and not be as mechanically interesting as you first thought.
For sacred geometry, I would highly suggest writing down your work so everyone can see the steps you took. It's one of those feats that quickly invokes a lot of numbers and can make people mentally check out and just accept what you say so as to not slow down play. As a GM, that's an annoyance at best. So, some due diligence on your part is reducing those potential pain points as much as possible.
As a GM, I'm not going to sit there and read your dice. That's your job. I only care if you're claiming a natural 20 when that's clearly a 2. I'm also not going to read your dice AND do math. Again, that's your job as it's your character and you took the feat.
I don't think taking a moment to look at die will take any longer to check him on his written out math as you suggested, especially when you don't know what the deuce he is doing with the numbers. Peeking at the die seemed totally viable to me. Plus it saves paper! :)
I don't think taking a moment to look at die will take any longer to check him on his written out math as you suggested, especially when you don't know what the deuce he is doing with the numbers. Peeking at the die seemed totally viable to me. Plus it saves paper! :)
Seeing a jumble of die (from the viewpoint of the GM) is very different from looking at numbers written on a line. Use a calculator on your phone to save paper. Not all "writing" involves paper. It's 2015!
example
It is incumbent on you, as a player, to prove your character is doing what it's allowed. Given the obtuse nature of that feat, yes, you need to show me how it works given it's wholly based on your unique combination of the rolls and is contingent on the player using their own intelligence that's not abstracted by the game. Simply rolling and claiming it works is grossly insufficient. Grouping die and saying something like "multiply these, add these, subtract those" is also insufficient.
How is that insufficient? You know it's always possible at 12+ ranks. If you can't trust your players at all, why play with them?
Relax mr. GM. The saves paper thing was kind of a joke, thus the smiley face. Plus the described method sounds like it would be more than just jumbled die. In fact it provides a nice visual aid to stuff like "these numbers cancel out". Seeing as you wouldn't be well versed in this odd mathematical trick since it isn't your character, you may find what is on paper confusing without a little help. This allows him to easily show what he did to you. Rather than him do it, put it on paper, hand you the paper, you begin to make sort of an "uuuuuhhh" noise, then he explains to you his due process anyway. Either way, the more I think about it, setting a number of times he can do this AT LEAST per encounter may be a smart decision.
EDIT: Honestly, how this will be done will ultimately be decided between him and his GM, mostly his GM, so I'm not sure debating on the how it should be done is all that relevant at this point. If it ever was.
YAAAAY! The truth comes out! This feat is nuts......
Oh, I agree it's a stupid feat. :D
The hoops is makes you do rather than just calling for a check do not give it any favors whatsoever. It's because of that which would require me to see your work. Yes, I realize how teacher-y that makes me sound. It's a teacher-y feat. It sounds exactly like one of those rote things a math teacher would do.
The point with showing your work is that GMs have a crazy amount of stuff going on in their head. Forcing them to put that on hold to look at your rolls and double work your math (which you're already required to do) passes a line for me. Break it down, treat me like I'm dumb (with respect to that feat), or no, it's doesn't work because f that feat.
Blinger Bunny, Idk if you ever plan to come back. But I may want to half way retract my statement. Just do metamagic like everyone else, without a limit on how many times you can attempt to do this this could get really tiresome. However as I have stated before, perhaps a limit of sorts could make this a tad less taxing on the group's patience? You doing this every time you cast a spell seems blugh.