Method for putting variance directly in Damage Formula?

[Damascus7]

Hi there! I'm making a skill that drains HP and MP at the same time, which is requiring me to use a somewhat complex equation. For now the formula is marked as HP Drain in the dropdown box, and has this formula:

m = Math.min(a.mat - b.mdf * 2, b.mp); a.gainMp(m); b.gainMp(-m); a.atk * 6 - b.def * 2

It does drain both correctly, the one problem I'm having is that the variance on the skill only applies to the HP drain part of the formula. Is there a way to put in a variance for the MP Drain as part of the formula?

For example, without variance, a given use of the Skill does exactly 24 MP Drain. I want it to instead have a 20% variance and do between 20 and 27 MP Drain. I tried using math formulas to do it, but since the formula only seems to handle integers, I tried multiplying the percent variance by 100 and then divide the whole thing by 100 afterward. It ended up looking like this:

m = Math.round((Math.min((a.mat - b.mdf * 2) * (Math.floor(Math.random() * 140) + 80)) / 100, b.mp)); a.gainMp(m); b.gainMp(-m); a.atk * 6 - b.def * 2

For the example given above, instead of landing between 20 and 27 like I want, it does 184 without any variance. So either my math is way off, or I'm not using the formulas correctly. Could anyone help me with this?

 

[bgillisp]

If you want it to drain between 20 and 27 damage, you would replace m with 20 + some command which gives a random number between 0 and 7. That will make it between 20 - 27.

 

[Damascus7]

No, I'm only using that as an example for comparison between what the attack would do with or without variance. It's not doing a set amount of damage, but a.mat - b.mdf * 2, and I just want it to calculate for a 20% variance.

 

[bgillisp]

I see now. The issue was indeed the math. I think you want * 40 instead, not 140, as * 140 is increasing it by 140%, not 40% like you want, as the variance is 40% of the total.

 

[Damascus7]

Thanks for that correction! I also realized I was accidentally using math.min instead of math.floor, and that i don't really need to use math.round. It still was not working properly, but then I ALSO realized that I had misplaced a parentheses or two in the math functions and adjusted accordingly. My new formula is:

m = Math.floor(((a.mat - b.mdf * 2) * (Math.floor(Math.random() * 40) + 80)) / 100), b.mp; a.gainMp(m); b.gainMp(-m); a.atk * 6 - b.def * 2

I also realized that as long as I have Math.floor at the end, I don't need to worry about decimals, so I simplified it further:

m = Math.floor((a.mat - b.mdf * 2) * (Math.random() * 0.4 + 0.8)), b.mp; a.gainMp(m); b.gainMp(-m); a.atk * 6 - b.def * 2

This seems to be working! I've tested it several times and the MP drain seems to be within 20% variance of expected values.

I can summarize this below for anyone else who needs help with this.

Where the original skill formula = [FORM], and the variance you want is x (30% = 0.3), your damage formula will be as follows:

Math.floor([FORM] * (Math.random() * (2x) + (1-x))

Thanks for your help! I guess I'm good at math, but bad at syntax.