Hello, i’m a novice proggramer, so you might find some mistakes or lack of optimization in my code, so feel free to correct me on anything or you wanna add something 
btw, if you find a post similar to this in the ue4 wiki, that post is also made by me
this is for HitScan weapons, but the same concept can be used.
Variables you need:
- Out Hit Distance (from a linecast, Hit Result Value).
- Base damage of the weapon (Example for guide: 12.0).
- Max range of weapon (Example: 5000.0).
- Three FloatRange type variables:
RampUpRange(0 - 900),
BaseDamageRange (900 - 1200),
FallOffRange(1200 - MaxRange).
First, we check if the OutHitDistance is in the base damage ranges, ramp up ranges, or in fall off ranges.
If the Out Hit Distance is in base damage ranges (900 - 1200), we simply just return the base damage.
However, if the Out Hit Distance is in the Ramp Up Range (900 - 0), we do the following Calculation:
NOTE:- you cant just copy paste this to c++ code, its not accurate to actual c++ ( cuz im dumb), this is basically how the formula might look like in in regular code.
WeaponDamage + (NormalizeToRange(MakeNegative(OutHitDistance), MakeNegative(RampUpRangeLowerBoundValue), RampUpRangeLowerBoundValue) * WeaponDamage).
The lower bound becomes max range of the normalize, and the Upper bound becomes minimum range (-900, 0).
For example, if the distance is 600, we make it -600, and compare it’s distance between (-900, 0) so if we are much closer 0 (Closer to target), we get more ramp up, but if we are closer to -900 (Further from target) we get less ramp up.
Please do not ask me how this works, i already used to much of my braincells trying to write this guide today.
dont worry about the fall off, its much easier
For Fall off the calculation is much simpler:
- WeaponDamage - (NormalizeToRange(OutHitDistance, FallOffLowerBoundValue, FallOffUpperBoundValue) * WeaponDamage)
for the (NormalizedToRange * WeaponDamage) part, i used this simple formula i learned in algebra class to find percantages:
- What(x) is (=) 50% (0.5) Of (*) 10, or X = 0.5 * 10
the result of the example given here is 5 because 50 % of 10 is 5.
Thanks for reading my guide, and please, if you want to add something doing or if you found any mistakes, correct me.
Bye!