Ofcourse, all credits to finding this go to SimplySarc: https://www.youtube.com/watch?v=aZp9olUXvOY
My video demonstration: https://www.youtube.com/watch?v=76XobG9QdOs
What is happening: When the Ravager attacks an entity, and that entity is shielding, he has a 50% chance to roar. For the first two seconds, he is stunned. After another 0.5 seconds, he roars, knocking back players within 4 blocks of him.
The math to apply the knockback is as follows:
double d0 = entity.locX - this.locX;
double d1 = entity.locZ - this.locZ;
double d2 = d0 * d0 + d1 * d1;
entity.f(d0 / d2 * 4.0D, 0.2D, d1 / d2 * 4.0D);(where "entity" is the entity being knocked back, "this" is the ravager, and entity#f is the function that applies knockback.
Due to this bad math (no clamping or divide by zero checks), our velocity can reach huge numbers. Conditions are simple: both entities must have very similar x and z values. (aka +-0.01 difference)
If the x and y are exactly the same (+-0 difference), NaN is added as the velocity, which thankfully doesn't break anything. Big enough values will crash a server (link), due to a too long tick / too many missed. See this for the crash: https://content.jame.xyz/sharex/mQRiWi3MfN.mp4
Edit 1: Here's the plugin used in the videos to test: https://github.com/electricman226/RavagerBug
As of 1.14.4-pre3, the knockback has been changed. (see here for the issue report)
The method to apply knockback now looks like this:
double d0 = entity.locX - this.locX;
double d1 = entity.locZ - this.locZ;
double d2 = Math.max(d0 * d0 + d1 * d1, 0.001D);
entity.f(d0 / d2 * 4.0D, 0.2D, d1 / d2 * 4.0D);With the Math.max method being used, the value is being clamped and protected against division by 0. The knockback is still strong, however the maximum possible is now much weaker than previously possible. This was not the intended change, as Mojang don't mind things like this that the average player cannot perform. The only intended change was preventing division by 0.
The most velocity I've been able to calculate you achieving is around ~125.0
See @1JackBlack1 comment below. (quoted here)
I know this is rather old, but your wording is unclear. Have you just tried putting in numbers to calculate the maximum velocity, or have you actually determined the maximum? On first reading it, I assumed the former.
If you did mean the latter, feel free to remove this post.
If the former, you can directly calculate the maximum velocity. Just focusing on x and y, the velocity squared will be (16/d2^2)*(d0^2+d1^2). This means we want d0 and d1 to be as large as possible and d2 to be as small as possible.
If we ignore the max condition this simplifies to 16/d2. That would mean d0 and d1 are unimportant with the velocity dominated purely by d2, which we want to be as small as possible, and the smallest it can be is 0.001, meaning the maximum in this condition is 16/0.001
If we are in the region of the max condition, we get 16*(d0^2+d1^2)/0.001^2 As d0^2+d1^2 < 0.001: 16*(d0^2+d1^2)/0.001^2 < 16*0.001/0.001^2 = 16/0.001 So again, the maximum is 16/0.001.
This means the maximum velocity is the square root of (16/0.001 + 0.2^2) = sqrt(16000.04)=~126.49
I know this is rather old, but your wording is unclear.
Have you just tried putting in numbers to calculate the maximum velocity, or have you actually determined the maximum?
On first reading it, I assumed the former.
If you did mean the latter, feel free to remove this post.
If the former, you can directly calculate the maximum velocity.
Just focusing on x and y, the velocity squared will be (16/d2^2)*(d0^2+d1^2).
This means we want d0 and d1 to be as large as possible and d2 to be as small as possible.
If we ignore the max condition this simplifies to 16/d2.
That would mean d0 and d1 are unimportant with the velocity dominated purely by d2, which we want to be as small as possible, and the smallest it can be is 0.001, meaning the maximum in this condition is 16/0.001
If we are in the region of the max condition, we get 16*(d0^2+d1^2)/0.001^2
As d0^2+d1^2 < 0.001:
16*(d0^2+d1^2)/0.001^2 < 16*0.001/0.001^2 = 16/0.001
So again, the maximum is 16/0.001.
This means the maximum velocity is the square root of (16/0.001 + 0.2^2) = sqrt(16000.04)=~126.49