What's the deal with reverse knockback?

[Kered13]

Sometimes when you land a certain moves, the victim goes flying in the opposite direction of the typical direction. This is well known with, for example, the reverse knee, and can make a big difference with whether you get a kill or not. But I haven't been able to actually figure out what triggers reverse knockback. Some moves do it pretty frequently, other never seem to do it (actually, as I think about it, I don't think I've ever seen a grounded move have reverse knockback). Looking at move data on the smash wiki it looks like there aren't special reverse knockback hitboxes, it just happens to the normal hitboxes.

So can someone give me a technical explanation of what causes this? Is it based on the orientation of the characters? Their positioning? Something else?

 

[Y-L]

Probably when you hit the back side of the hitbox. i.e. here

 

[Praxis]

I'm curious myself why it happens, because when you look at hitbox diagrams the hitboxes are programmed to send a certain direction. Why does the back do the opposite?

 

[Hinichii.ez.™]

Probably when you hit the back side of the hitbox.

Call it a hunch, but I think this is correct.

 

[DrinkingFood]

It's not the back half of the hitbox. It doesn't have anything to do with the hitboxes directly, actually. It's based on which side of the attacking character you are on. If your character's center is in front of their character's center, it sends forward. Behind them gives a reverse hit.
Moves that send over the shoulder, like peach's/Samus's dsmashes, actually only have one angle applied to all of their hitboxes, even those they can either send you from their front to behind them or from behind them to in front. How the characters are positioned with respect to each other determines what orientation of the assigned angle is used, or rather determines whether left or right direction is assigned positive on the x-axis.

 

[sunshinesan]

On a related note, does Falco's bair reverse knockback's power depend on the time in which it connects or which hitbox connects, i.e. the back leg vs the front one.

 

[Kered13]

It's not the back half of the hitbox. It doesn't have anything to do with the hitboxes directly, actually. It's based on which side of the attacking character you are on. If your character's center is in front of their character's center, it sends forward. Behind them gives a reverse hit.
Moves that send over the shoulder, like peach's/Samus's dsmashes, actually only have one angle applied to all of their hitboxes, even those they can either send you from their front to behind them or from behind them to in front. How the characters are positioned with respect to each other determines what orientation of the assigned angle is used, or rather determines whether left or right direction is assigned positive on the x-axis.

This makes a lot of sense. I was looking at the hitbox data for Falco's down smash earlier, it has two hitboxes that have the same angle, but obviously it sends the opponent away no matter which side hits. So any move with a hitbox that goes behind the center is capable of reverse knockback.

 

[Narpas_sword]

Probably when you hit the back side of the hitbox. i.e. here

In our circle, thats the 'correct knee'

It a reverse knee when falcon knees the opponent the way falcon is facing.

 

[DrinkingFood]

This makes a lot of sense. I was looking at the hitbox data for Falco's down smash earlier, it has two hitboxes that have the same angle, but obviously it sends the opponent away no matter which side hits. So any move with a hitbox that goes behind the center is capable of reverse knockback.

Hitboxes don't have to reach behind the attacker to hit the opponent while their center is behind you. They only need to not reach too far in front of the attacker for a limb or just the width of the opponent's body to cross the gap from *behind the attacker's center to *the edge of the hitbox*

 

[Y-L]

That was just a blind guess don't quote me on anything, DrinkingFood sounds right and is always on point with frame data.

 

[DrinkingFood]

Not always, I got Zelda's grab wrong and some other things sometimes :'|
But I always remember when I'm corrected at least

 

[Kered13]

Hitboxes don't have to reach behind the attacker to hit the opponent while their center is behind you. They only need to not reach too far in front of the attacker for a limb or just the width of the opponent's body to cross the gap from *behind the attacker's center to *the edge of the hitbox*

Hmm, yes that makes sense. So does this mean that some moves that aren't normally expect to have reverse knockback might do it on large characters? (EDIT: Yeah, looks like that's correct, I was able to get reverse knockback with Sheik and Marth's fairs on Bowser.)

Thanks for that explanation.

While I'm on topic, if multiple hitboxes (from the same attack) hit at the same time, what are the rules for determining which hits? For example, if Falco used his downsmash you might hit both the inside and outside hitboxes at the same time.

 

[DrinkingFood]

Hmm, yes that makes sense. So does this mean that some moves that aren't normally expect to have reverse knockback might do it on large characters? (EDIT: Yeah, looks like that's correct, I was able to get reverse knockback with Sheik and Marth's fairs on Bowser.)

Thanks for that explanation.

While I'm on topic, if multiple hitboxes (from the same attack) hit at the same time, what are the rules for determining which hits? For example, if Falco used his downsmash you might hit both the inside and outside hitboxes at the same time.

Yep, that's exactly how it works. However, the majority of moves can reverse hit anybody, especially with interpolation factored in. Marth's fair and sheik's fair both have shoulder hitboxes (at least I think sheik's does not 100% sure though) that can hit any size opponent behind them if a limb sticks into the hitbox from behind or even just the fine of a round character's body like Kirby/jiggs. Mostly the character's size effectively increases The area on the body in which you can land a reverse hit, making it easier on big characters.

As for the second question, hitboxes are assigned ID numbers starting from 0 and increasing. Lower numbers have priority, so hitbox 0 and 1 hit at the same time, hitbox 0 is the one that takes effect and hitbox 1 is ignored. In most cases, the closer a hitbox is to a character's center, the higher priority it has, meaning its ID is 0 or closer to 0.

 

[Spralwers]

It's not too uncommon for grounded moves to have reverse hit boxes either. The most common I think would be jabs. I know at the very least, Ganondorf and Falcon have reverse jabs.

I think its quite hilarious and definitely fits into the "character" of smash to have reverse hitboxes.