How to calculate knockback like super smash bros?

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#1

Heyo I’m currently working on a fighting game which is in a similar style to Super Smash Bros and I’m currently trying to add knockback I’ve found the formula used in Super Smash Bros and I’ve been trying to use and understand it, but I’m a bit stuck and could use some help getting it to work. I’m using these resources to help me out Knockback - SmashWiki, the Super Smash Bros. wiki (ssbwiki.com) and Smash Ultimate Calculator (rubendal.github.io)

Basically this is the formula used to calculate knockback (I’m pretty sure atleast)
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  • p is the percentage of the target, counted after the attack’s damage is added.
    • In Melee , p is floored pre-hit percentage + stale attack’s damage.
  • d is the damage the attack dealt.
    • In SSB and Melee , it is the full damage without counting stale-move negation, except for [projectiles, which use the stale damage.
    • In Brawl , it is the damage including the staleness or the freshness bonus.
    • In Smash 4 and Ultimate , it is the damage including 0.3x of the staleness or freshness bonus.
  • w is the weight of the target. It is set to 100 if the attack is weight independent. Note that in SSB , heavier characters have a lower weight value than lighter ones, in accordance with the formula.
  • s is the attack’s knockback scaling (also known as knockback growth) divided by 100 (so a scaling of 110 is input as 1.1).
  • b is the attack’s base knockback.
  • r is a series of ratios based on a number of factors

Here is how I’ve tried to use this

		
		local MoveData = {
			Damage = 23,
			KBG = 98, --knockback growth
			BKB = 25, --base knockback
			Angle = 361,
		}
		local Damage = MoveData.Damage
		Target.Percent.Value += Damage
		local Percent = Target.Percent
		local Weight = 100 --would be weight of the target
		local KBG = MoveData.KBG
		local Scaling = KBG/100
		local BKB = MoveData.BKB
		local Ratio = 2.0
		local KnockbackCalculation = (((((Percent.Value/10 + Percent.Value*Damage/20) * 200/Weight+100 + 1.4) + 18) + Scaling) + BKB) * Ratio
		local LaunchSpeed = KnockbackCalculation*0.03
		local Knockback = Instance.new("BodyVelocity")
		game.Debris:AddItem(Knockback,0.3)	
		Knockback.Parent = Target.HumanoidRootPart	
		Knockback.Name = "Knockback"
		Knockback.MaxForce = Vector3.new(1,1,1)*5000000
		Knockback.Velocity = Player.Character.HumanoidRootPart.CFrame.LookVector*LaunchSpeed + Vector3.new(0,LaunchSpeed,0)
	end

Result. Despite the dummy having a high percent the knockback is basically nothing.

5 Likes
#2

Have you tried putting prints in to see the values of the variables?

#3

As you can see in the formula (I cant see cus I am in dark mode lol) there are a number of constants. Try tweaking these as many different game engines use different measurement systems and it could be that the measurement system was originally in metres.

#4

Try increasing the time!

game.Debris:AddItem(Knockback,0.3)

to

game.Debris:AddItem(Knockback,0.6)
#5

Just tried this but it doesn’t really affect it at all.

Honestly I probably don’t need to all of this and should probably simplify it, but I’m not good at math so I’m not sure how, but all I need or atleast all I think I need is 2 values one for how high it goes and how far it goes, but I’m having a hard time figuring out how I could make those values. Would you happen to know a solution? lol

#6

Have you tried taking your entire calculation for the Knockback Velocity and multiplying it by a flat value, like say 10? Your Knockback looks very similar to Smash, but it needs more force to fit the Roblox engine.

1 Like
#7

The knockback is exactly from smash lol. Anyways no I’ve not tried doing that I’m not sure what you mean though are you saying to multiply this by 10? (((((Percent/10 + Percent*Damage/20) * 200/Weight+100 + 1.4) + 18) + Scaling) + BKB) * Ratio if so I don’t know how that would help because I already get a big number from this like 415 which will send the dummy flying if I try to use it or are you talking about this BV.Velocity = Player.Character.HumanoidRootPart.CFrame.LookVector*HorizontalValue+ Vector3.new(0,VerticalValue,0)

#8

Multiple BV.Velocity by 10 and see if that gives desirable results.

#9

LOL yeah this defiantly didn’t workout

I added prints and heres what everything equals:
Knockback = 517.36
LaunchSPeed = 15.5208
BV Velocity = -0.6626876, 155.207993, -15.5066462

Edit: do you know any other way I could get values for this?
BV.Velocity = Player.Character.HumanoidRootPart.CFrame.LookVector*HorizontalValue * 10 + Vector3.new(0,VeritcalValue,0)

#10

How about changing the max force higher;
if that does not work try to find the weight of the target

Knockback.MaxForce = Vector3.new(1,1,1)*math.huge

function GetModelMass(Model)
local Mass = 0
for i,v in ipairs(Model:GetDescendants() do
if v:IsA("BasePart") then
Mass += v:GetMass()
    end
  end
return Mass
end
1 Like
#11

Yeah… maybe 10 is a bit too high. You can probably lower it to around 2 ~ 3 to get a knockback effect with a similar magnitude to Smash. Also that value looks about as good as you can possibly get it.

#12

Yeah lowered it down a bit and it seems to work a bit better now however it’s defiantly still a bit wack although it works so I guess I just gotta improve it overtime here’s how it currently works.

1 Like