I will try to summarize my results to a practical simplification for people that are not willing to read the lengthy explanation of how it works. However, as the mechanics at play are quite complex, to truly understand when it works, you will need to understand how it works. For the sake of simplicity, the summary isn't necessarily technically correct. If you don't know what hitlag and SDI is, watch the following video first, by Kadano : https://www.youtube.com/watch?v=7RP3sbS7Dm0
Summary / practical simplification:
Every Melee player knows about crouch cancelling and the majority knows about ASDI Down. ASDI Down allows you, when grounded, to land after the hitlag of a move that does not induce too high of a vertical velocity upon your character. It is performed by holding at least partially down on the C-stick, or on the directional stick, assuming you don't input something a non-downwards direction on the C-stick at the same time.
Crouching refers to entering the crouch animation, which will reduce the hitlag and the knockback of any move hitting you to 2/3 of the original values. As it is done by holding down on the directional stick, unless counteracted by the C-stick and assuming the stick isn't put back near the center, it will trigger ASDI Down. Therefore crouching usually refers to being in the crouch animation, and ASDIing down.
These base mechanics allow slideoffs and Amsah techs to exist.
Do note that when I say ground, I'm referring to either the ground of the map, or a platform.
Landing at the end of hitlag is actually possible when airborne. To trigger it, you need to be nearing the collision point with the ground in the damage animation that hit puts you in. Then, if the "Automatic SDI" is enough to counteract the vertical velocity induced by the move and make you collide with the ground (with the slight help of gravity), you will land and depending on whether the move would have made you enter tumble, you will land normally and be actionnable 4 frames later (no tumble) or miss-tech / tech if you've inputted one in the last 20 frames and before hitlag (tumble) - the same way it goes when grounded.
To be close to this collision level, you could SDI and approach the ground this way. However you can't just have your way and ignore collisions when SDIing, or that would mean you could go into the stage or through it, and for example, go under Battlefield when sent upwards and tech on it. The game has a mechanics to prevent you from doing this, which iscommonly called Forbidden SDI.
Forbidden SDI nullifies the vertical movement from any SDI that makes you leave the ground when grounded; and alters any SDI that makes you collide with the ground when airborne. The position you end at is the one you would end were this SDI to be accepted, but your vertical position is reset to be a above the ground, how much being character and damage animation dependant.
Due to this, SDIing near the ground and hoping to land is a gamble for most characters. If you graze the collision level, you may land. The closer you are, the higher the vertical velocity you can handle. If you go too far and collide with the ground during hitlag, you will be teleported back above the ground at a height that depends on your character and the damage animation you're in, which in turn will define how much vertical velocity you can take and still land from your ASDI.
But for Peach, there is no gamble. Because Peach's vertical position when floating is constant, despite her body oscillating visually. This means if you are hit out of a float or an attack done from that float, for a given float height and a given damage animation, there is a SDI angle that makes you graze the ground and land from hits similarly to what ASDI Down allows you to do when grounded. So to speak, you can simultaneously float, and tank hits.
The inputs are the following :
SH Float refers to short hop float. If you don't know what subfloat and short hop float are and would like to know, check respectively https://smashboards.com/threads/sub-float.455068/ and https://smashboards.com/threads/my-thread-for-random-peach-stuff.452881/#post-22235176 .
The values above are limits. Input the tick below it and you might trigger Forbidden SDI. This means you should aim above them. Being 10% of the stick down-to-center distance above the perfect angle will only make you fail the landing if 120% of the knockback would have made you fail. Being one tick below triggers Forbidden SDI.
For Peach, triggering Forbidden SDI means no landing whatsoever for moves that put her into tumble. However for moves that don't put her into tumble, she is put close enough to the ground so that she can still land against weak enough moves. You can actually land post forbidden SDI if you can land from a subfloat without active smash DI, with ASDI down only, which you can the vast majority of the time. In this situation, Peach can land from vertical-sending hits that have up to ~65% of the knockback it takes to enter tumble. For your most common angle, the Sakurai angle, which is approximately a 45° angle, you can land at nearly any knockback that doesn't make you tumble. Precisely, you can take ~87% of the knockback that would make you tumble. If you DI these down, you are guaranteed to land.
But if you're freaking out, be careful with these numbers : knockback is not at all proportional to the damage % before hit. For example, Peach can only successfully land with only a buffered ASDI Down from a subfloat against an unstaled Fox utilt (airborne characters hitbox) DIed full away (approx vertical) at 0%. From 1% onwards, it doesn't work. And it only puts Peach into tumble from 24% onwards, meaning that the knockback on Peach starts just below 65%, and reaches 100% at 24%.
Now as to how to execute the smash DI, there are a few things that are worth keeping in mind :
- If you transition from an horizontal input to the angle you're looking for, you will SDI (only once) as soon as the game polls you out of the "vertical deadzone". So the vertical part of your SDI will probably be strongly weakened when inputting it this way. Due to this, going to the deadzone and inputting the angle from the center of the stick should be more reliable (and accurate).
- With the 2nd method, your controller might still be polled in the SDI area, before reaching the rim. This will very slightly weaken your SDI but should only very rarely make the motion fail.
- In case you were attacking and it trades / gets interrupted, what should've been your fastfall input can be your SDI.
I think that's it for the how.
Aside from the usual uses of sticking to the ground when hit - CC attacks, slideoffs, amsah techs - it's worth noting that this can be executed from a trade.
This effectively turns your aerial into the logical equivalent of a 4 frames of ending lag move hitting on its last frame, which means an excellent combo starter.
You can also Amsah tech if the trade makes you go into tumble and gain a positional advantage in doing so.
I've made a few gfys to show what the interaction looks like when your aerial trades. Use the gfycat links to have access to the frame advance.
Peach may be the only character that can reliably know its vertical position and work with it, however, some characters don't even need to, and even have much better data regarding how much they can take and still land. They however lack the ground proximity that comes with floating.
As said previously, "randomly" SDIing into the ground will put your character above the ground, how much being character specific. This "how much" defines your minimal shot at landing from a hit. Collide with the ground, his height applies ; graze the ground, the vertical velocity resistance in the area near the ground peaks at the collision point, at a value that's character specific and progressively worsens as you're farther away from the ground, until you cannot land no matter the hit.
That means that if you SDI "low enough", this including for some characters a character specific area before the collision level, you will get at least the resistance to knockback you get after a forbidden SDI. This resistance, in % of what you can handle on the ground and still land, is the following, per character, for move that do not tumble and have a knockback that's still decent (65% of the knockback required to tumble ; things are usually similar for weaker moves but I have not yet compiled the data) :
You've read that right, some characters litterally have a 100% and can handle the same vertical velocity as they could were they grounded, after performing a forbidden SDI. Namely, Jigglypuff. This is due to these characters having particular collision properties. This means that if these characters SDI down and collide with the ground during hitlag, they are able to land after any hit they would have been able to take without leaving the ground, on the ground. (= A lot of them). For the characters that have a 100% here, that also applies to moves that put you in tumble.
ICs' stat may not look as impressive, but considering what we've said above about what Peach is able to do with her 44,76% stat, that means Popo can nearly always (From my few tests Nana can't SDI, feel free to correct me) land if the move doesn't make them go into tumble.
But how much do you need to SDI to "collide with the ground during hitlag" ? Not that much, actually. 2 SDI are more than enough if we are decently close to it.
The following image is a Puff that is one vertical SDI and one near-vertical SDI away from the ground (Y=~11,5) :
The following image is a Puff that is one vertical SDI, one near-vertical SDI, and the ASDI away from the ground (Y = ~14,43):
For comparison, the peak of Jigglypuff's short hop is Y=9,1461.
This means that it's certainly humanly feasible to reach the ground in plenty of cases. All characters also move the same distance, 6mm, when SDIing.
If you aren't horrified yet, you either don't get what this means, or you're a Puff main.
Either way, here is what it allows one to do in video :
I think that's it for the technicalities-less summary. Please tell me if there is anything that's unclear in this section. While with few numbers, this should give you a good understanding of how it works. The how much comes afterwards.
The reason I haven't used many numbers or provided accurate rules for all characters regarding how much you can take - before not being able to land - in comparison to what you can take when grounded, is because it's complicated and relies on specifics of the game mechanics (ex. ECBs). For example no matter the input, Peach, when hit in the middle of the body, will only ever be able to take ~70% of the knockback before she can't land anymore. But get hit in the leg, and with the right input, you can go bey... take ~140% of the vertical velocity that would make it impossible to land grounded, and still land. It's unintuitive to say the least. The following explains how things precisely work in the game's engine. If you want to truly get it formula-wise, so you can lab on top of it, continue reading.
You need to know how collisions are handled in Melee and how SDI works precisely. For this, I suggest watching these excellent videos by the lab legends schoomblidon and Kadano :
"The mechanics behind advanced platform tech" by schmooblidon : https://www.youtube.com/watch?v=TtiDd5cQWJc
"Teching and avanced DI (Double Stick DI, Multiple Smash DI)" by Kadano : https://www.youtube.com/watch?v=ZkdPVUlrSOo
You don't actually need to watch the full platform tech video, but the more you see, the more you check that your understanding of the ECB is correct. It's also more Melee knowledge.
On that subject, I'd like to thank Kadano for its informative videos and overall Melee labbing, schmooblidon for this video and creating ikneedata.com, T tauKhan for answering my SDI related questions, Magus420 for creating the Magus display, Achilles1515 for creating the 20XX Melee Training Hack Pack, and their other works, and all those that have contributed to build the current pyramid of Melee knowledge and the available labbing tools available.
It's only by building on the work of others that I can contribute to the Melee metagame by coming up with this in a humanly realistic amount of time.
Now about the technique : you can't actually land during hitlag. The collision is simply not evaluated, or rather, it is, and it triggers Forbidden SDI if you collide. The first frame at which you can land is the frame following hitlag. During all of hitlag, you are in the first frame of your the damage state your character entered when hit. This damage state is chosen at the first frame of hitlag, it is not affected by whatever happens during hitlag. During the hitlag bar the first frame, you can SDI as per the rules described in Kadano's video. At the first frame following hitlag, ASDI occurs. At this frame, you are in frame 2 of your damage state. You are also affected by the first non-null velocity due to your character's gravity (and therefore downwards acceleration, here the movement between the last frame of hitlag = downwards acceleration * (1 frame)² ).
You will land if the bottom of your ECB touches the ground. Your character's ECB's position is your character's position plus an offset that is, except in case of delayed updates, a consequence of only your character's state and which frame of the associated animation you're at. I have not encountered a case where the ECB bottom offset is not either the default values for the current state;frame couple, or a past value that has not yet been updated.
ECB updates oddities have been gone over in depth in schmooblidon's video. The ECB bottom offset is frozen for an amount of time when leaving the ground or double jumping.
Depending on how you leave the ground, your ECB offsets are frozen for 9 or 10 frames. Jumping means 9 frames spent in an animation with the ground's ECB. Running off means 10, I believe. And so does getting hit.
As we said before, the collision can only occur on the frame after the hitlag. That means, when being grounded, that if the hitlag is 9 frames or less, if we are to call the first hitlag frame frame 1, the collision frame is frame 10 or less. So during the frame it all happens at, your character has the ground ECB, the ground ECB being, I believe, always 0. This applies to move that deal up to 20% of damage when non electric, or up to 11% when electric. (The electric effect multiplies the hitlag by 1,5). If the move does 21% damage or more, or does 12% or more and has an electric effect, the hitlag is of 10 frames or more, which means the collision frame is the 11th or later, which means the ECB is no longer the grounded one, which is what Kadano talks about in his video when he mentions Falcon's knee, and that you have to attempt to graze the ground with a 305° degree input.
The SDI for all characters moves you 6 melee meters, the ASDI for all characters moves you 3 melee meters, the melee meter being the standard length unit in SSBM. I'm going to assume the ASDI is a clean (0;-1) on the C stick, which means the ASDI's movement is (+0;-3). When being off, the vertical movement can be slightly shorter.
The check for whether you collide is therefore, on frame n° "hitlag length+1".
(Y position + ECB Bottom offset - ASDI_y) <= 0, with the ECB bottom offset being, depending on whether it's updated or not, respectively the value associated to this state;frame couple, and 0.
Which is equivalent to
(Y position before the hit + frame 2 ECB Bottom offset + (frame 1 hit Y velocity)*frame - |character's downward acceleration * frame²| - 3) <= 0
Which I'll refer from now on as
(Initial position + F2 ECB offset + initial hit Y movement + initial character Y movement - 3) <= 0
This formula, along with the fact all moves below 20% have 0 as their F2 ECB offset, explains the consistent results you get when labbing Amsah tech percents on ikneedata.com . With the initial position being 0, the check for whether you land is simplified to :
Initial hit Y movement <= 3 - initial character Y movement.
The initial character Y movement is also a constant per character. For Peach, it is -0,08.
So the check is now : Initial hit Y movement <= 3,08 ; which applies to all move, and is really simple to work with. In what follows, I'll use Peach's value directly so it's simpler.
The airborne check is : Initial position + F2 ECB offset + (Initial hit Y movement-0,08) <= 3.
If you SDI, the check is now : Post SDI position + F2 ECB offset + (Initial hit Y movement-0,08) <= 3.
With that position being affected by the forbidden SDI rule. This rule, accurately expressed, says that if you collide with the ground during hitlag, you are projected at level Y=0,001.
The check for colliding during hitlag is : Post SDI (pre rule application) position + F1 ECB offset <= 0.
Side note, in case that's unclear, ECB bottom offsets are always positive.
This means that you can lower your position up to "- F1 ECB offset". If it's 0, then you can't go into the ground, if it's 5, then you can enter negative vertical positions, as long as you don't reach Y=-5 or below. And it's going to be necessary. Let's say this F1 ECB offset is -5.
If your F2 ECB offset is -5 as well, by nearing Y=-5, you can get the same landing abilities as you would have when grounded, as your collision check is now :
Post SDI position (~-5) + F2 ECB offset (5) + (Initial hit Y movement-0,08) <= 3 ; Initial hit Y movement <= 3,08 ; just like it is on the ground.
If your F2 ECB offset is -1,92, you will end up with -3,08 + (Initial hit Y movement-0,08) <= 3 ; Initial Y movement <= 0. No matter what you do, you cannot land. Your animation doesn't allow you to.
Now, if your F2 ECB offset is -8,08, you will end up with Initial Y movement <= 6,16; which mean you can take moves whose knockback is twice as high as what you could take on the ground, and land regardless.
The position you can be at when the collision is evaluated depends on the ECB offset associated to the first frame of the damage animation, while the collision itself uses the ECB offset of the second frame.
This emphasizes the importance of the animation your character enters when hit on the effectiveness of the technique.
I'll call from now on 1-(Post SDI position + F2 ECB offset)/3 the warping strength (WS). Or 0 if it's negative. The formula becomes : (Initial hit Y movement - 0,08) <= 3*Warping strength.
"Initial hit Y movement - 0,08" is the position the character ends up at on frame 2 if you don't ASDI during the collision frame, so this allows easy labbing. And for comparison, when grounded, the warping strength is always 100%.
Sidenote, I've noted the velocities induced by a move appears to depend on whether the target was grounded or airborne. I don't know why ; what I've forgotten to account for. Does the previous momentum matter ? I'll edit this when I find the source. Ikneedata's calculation match the values I get for grounded opponents.
In the previous example, the animations respectively allowed 100%, 0%, and >200% warping strength.
So now let's talk about the damage animation you can enter when airborne.
There are 8. I believe 9 other animations exist, but are ground specific.
The following table show the animation names, along with their frame 1 and 2 bottom ECB extension, and the maximum warping strength achievable in the animation.
Unfortunately I don't know yet how to study the game's assembly code, so I can only make assumptions from empirical testing as to the rules that decide which animation (= state) you enter.
DamageAir1, DamageAir2 and DamageAir3 are the animation you enter when a move doesn't put you in tumble. I believe the differenciation is done based on knockback.
[0,~25]KB : DamageAir1
[~25,~52]KB : DamageAir2
[~52,80[KB : DamageAir3
DamageFlyLW,DamageFlyN,DamageFlyHi and DamageFlyRoll are the animations you can enter when being hit into tumble by a move whose base angle isn't above 70° (or is above 110°, borders excluded).
For all the hits that qualify, if you are above 100%, there is a 30% chance you will enter DamageFlyRoll. When it triggers, it takes priority over other animations.
When it doesn't, or when you are strictly below 100%, which animation you enter appears to depend on "where" the character's body was hit. The precise mechanics are quite unclear to me here, especially considering the hitbox that connects (and has the highest priority among those connecting) can touch a large portion of an opponent's body. It doesn't appear to be linked directly to the difference in vertical position between characters, but I haven't tested it in depth.
So as you could guess from the names, DamageFlyLW, DamageFlyN and DamageFlyHi respectively occur when you were hit low, in the middle, and high.
Finally, a character enters DamageFlyTop when being hit into tumble by a move whose base angle is between 70° and 110°, borders included.
For each of these animations, you would ideally want to be a tiny bit above the position " - frame 1 ECB offset ". At the limit, you then get the maximum warping strength computed in the table above. The formula for it ends up being (3 - frame 2 ECB offset + frame 1 ECB offset)/3.
Now, to get to this position, you will need to SDI just the right vertical amount. The amount you want to travel vertically with SDI is at close as you can (more, and you trigger forbidden SDI) to (initial position + frame 1 ECB offset). This means that for every (float height ; animation) couple, there is a distance to travel to get into the best position. Assuming we use the 3 float heights you can reliably get at (regular float and short hop float do not require frame perfect inputs, and subfloat has an audio & visual success confirmation, and transitions into regular float or short hop float if failed), that's 24 different distances, each of them has its own angle. We'll simplify the execution in the end, but for now, here is the full lab data :
How we've got here should allow you to understand what the tables mean. From left to right, the top row gives :
- The ECB offsets associated to Peach's aerial damage animations.
- The distance you must travel from the (float height ; character state) couple, to get to the lowest possible position during hitlag.
- The Y value corresponding to this distance. Since we want to only do one SDI input, here it's limited to 1.
- The angle on the stick associated to that Y value, i.e the highest angle that doesn't trigger Forbidden SDI.
The following gfys are example of the technique succeeding and failing, done on a subfloating Peach, that does a Y=-0,6125 SDI (and (0.7875;-0,6125) DI) on a strong unstaled Fox nair. With this DI, Peach can Amsah tech it at up to 186% on the ground.
In these gfys, the Magus display at the bottom shows the character's position on the left, its ECB bottom offset in the middle, and its total velocity (hit velocity - 0,08) on the right. Also, the gfycat site has a frame advance.
For the last gfy, Peach is at height 0,0001; the SDI puts her at -3,6749, which is fine since her F1 ECB offset is 3,68470. On the collision frame you can see that she landed (Ypos = 0,0001), that her F2 ECB offset is 2,47309, and that her total velocity is 4,19388, which is coherent with a warping strength in this example of near 140%, which means able to handle nearly 4,2 total vertical velocity.
At 266% percent, the total vertical velocity is 4,23654, which she can't handle.
Now about the tables given in the first part, the values given are those that don't trigger Forbidden SDI, for DamageAir3, DamageFlyN, and DamageFlyTop.
As non-tumbling moves that don't make you enter DamageAir3, I believe, have less than 52kB, it should be safe to assume that even if you trigger FSDI, a WS of 47,67% is more than enough to land. Same thing for DamageAir1.
As for DamageFlyLw, it's actually so rare that it occurs when floating that you shouldn't care about it. I had to make a custom battlefield because it was so hard to get that animation on the ground.
Hence the minus the values for the 3 lines being respectively the values for DamageAir3, DamageFlyN and DamageFlyTop, truncated to the 1/80th below.
Now as to what occurs if you attempt a forbidden SDI, as said earlier, "if you collide with the ground during hitlag, you are projected at level Y=0,001." That means that you end up in the same situation as a SDI-less subfloat. Which is pretty good for moves that don't put you into tumble, but won't do it for moves that do. You will get the following WS (extracted from the sheet above) :
I think that does it for Peach specific things.
Then again, it's not truly Peach specific, but Peach has the advantage of knowing its precise height, which in turns allows you to know which angle to input. With most other characters, you're hoping not to trigger Forbidden SDI as it most likely means you won't land. But not for all characters. Puff, DK, and G&W always have a bottom ECB extension equal to 0. So for them, Forbidden SDI just puts them back "on the ground", where they have a WS of 100%.
For other characters, your ECB F1 defines your position sweetspot and defines how much above it you're put at if you trigger FSDI, your ECB F2 defines where you have a 100% WS (or would have if you can't reach it), you start having a positive WS at ECB F2 + 3 and gain more moving down from there.
I may eventually draw charts to illustrate the problem for other characters but if I keep trying to add more stuff right now this isn't getting published ever.
For an example of FSDI, compare these two gfys : https://gfycat.com/FantasticAggravatingFlee vs https://gfycat.com/MerryDisfiguredBonobo
Sheik's data isn't as easy to obtain as the others due to most lab tools showing Zelda's data even when she's in Sheik form, and I haven't found or estimated it yet.
For medium and high post FSDI WS characters, this opens the way for some seriously ugly things. Especially for 100% Post F-SDI WS characters. Nothing wrong can happen when SDIing down, if you touch the ground, you're not getting teleported to a position you can't land at. And SDIs go far. One eighth of circle SDI (Down -> near down) gives 2 SDI that, if both are applied, make you travel ~120% of Jigglypuff's short hop height.
This makes the two Puff gfys above realistic besides the Rest aiming that I certainly wouldn't try in bracket. (https://gfycat.com/UntimelySpiffyBunting ; https://gfycat.com/HotGiganticDartfrog ) They only took 2 SDI to perform. So, yeah, that's pretty strong.
Finally, all of this also works on platforms, and actually, there is nothing forbidding you from going from below a platform, to above one. You're only forbidden to go from above to below. That means you could actually teleport on the platform above you by SDIing upwards then ASDIing down.
The simplified table provided is a simplification indeed - if you know you may get hit below because you're floating on a platform dairing, then you should go with the angle for DamageFlyLw that you can find in the tables. If you're sure someone will hit you above, and you're at a % so high that the ~6% of WS you can gain by going for the DamageFlyHi limit can make a difference, then go ahead and use that angle.
There are also optimisations to be made when you attack a player that appears to be walling with a float aerial - you can group a SDI attempt that's Y<=-0,7 and your fastfall input. Or do your fastfall input normally and enter the quadrants nearby to get an extra SDI.
I've also barely mentionned DI, but it determines the vertical velocity we're trying to counteract, and how much latent horizontal momentum you have when landing. So ideally you'd want to choose your SDI or adjust your stick position after the SDI by taking into account the fact DI. The closer you are to that move's combo DI, the longer you can land, but the more latent horizontal momentum you have after landing.
This in turn opens the way for choosing which float height you want to be at for an easy access to good landings. The most obvious thing being Subfloat at low percent. You can handle ~52kB of an upwards sending move (ie DamageAir2 moves), ~70kB for a move sending at the Sakurai angle, if it's a Sakurai angle DIed down, you can handle all non-tumbling knockback, with only ASDI down buffering from Subfloat, or ASDI buffering and SDIing into the ground at any angle from higher float heights. And if you trade, you act 4 frames after hitlag ends, so to speak, after the hitstun of your opponent starts. Frame-wise, it's incredible as a combo starter. Only shines and obscure grounded moves (G&W utilt ?) are on that level. That makes a floating Peach at low % extremely scary as you can so to speak, crouch and attack at the same time, with persistent hitboxes that can be interrupted laglessly at any time. To fight them the opponent must not only outdisjoint them but do it in a way that's not weak against Peach landing after the hit, either by landing themselves (grounded options or teleporting onto the ground) or by spacing so that Peach cannot reach them in time. This also fits perfectly into the playstyle modern Peach is heading to, staying close to the ground with only half-commits, persistent and interrupted floats, to have tight control over your movement instead of repeatedly committing to high floats that give you strong options but limit their diversity, while your opponent still has access to all of his on the ground and can use it to accurately space and outdisjoint your aerials with theirs, which makes that interaction there get worse the better the opponent is.
You could also use it along the various Peach movement options above a platform, to improve situations where you're close to the platform, or in many specific situations such as Marth doing a weak uair on you due to vertically overshooting to hit an aborted float... There are many, many possibilities. This post isn't as much a technique presentation as it is a game mechanics explanation that can be used to lab improvements for specific situations.
And that should be all. It's the first time I lab something of this size, and the first time I post something outside the Peach R&D FB group. So, the organisation, format, and the overall presentation most likely suck. Feel free to comment on anything I could change or add to make the post clearer, correct me on the content or complete it. I hope it helps and makes the game more fun and interesting. Thanks again to those that made this possible.