Question about Knockback

[vortex]

I was curious if anybody knew anything about the specifics of Knockback.  ie., What is the number in the intensity indicative of?  Is it a % chance?  Distance thrown?  Does anybody have any specific formulas?

Thanks much for any help!  :wub:

[crocodamon]

i have the same damn question  :banghead:

[stumpy]

It's not quite that simple. As best I can tell after much testing, knockback is the physical impulse (change in momentum) applied by an attack.

I am pretty sure the "knockback' number you see in the power design dialog is related to (scaled up) KB applied during play by that power. Of course, during game play, that number is just the center of a range where some randomness is added to make things more interesting and realistic, just like with damage. Also, the scaling is pretty large. KB of say "20" on the power dialog might mean actual KB of around 15000 in game units applied when you use that attack during play.

Objects have a minForce value, that's usually based on mass. If the actual KB applied by an attack is larger than the target's minForce template attribute, then the target is knocked back. If it's less, he ignores it. Makes sense, right? When applying knockback, more massive characters will take less than the featherweights. That's why it seems that there is sometimes knockback from a power and sometimes not: attacks with KB always apply some KB when they hit, but when the KB is less than the target's minForce, you don't see anything happen.

When a character is knocked back, that KB is actually an applied impulse, so dust off your high school physics book. (Same thing for Trigger_Force() for any scripters reading this.) In other words, the knockback divided by the target's mass is the change in his velocity.

So, assume that my character has a mass of 80 and a minForce of 8000 and he is hit by an attack that does KB. If the KB is less than 8000, it does nothing to him. If it's over 8000, it knocks him back by some amount by giving him a velocity that sends him flying or tumbling on the ground or into something next to him. So if the KB was 16000, then his velocity will be 16000/80 = 200 game units/sec, which is roughly 20meters/sec.

Of course, the KB from a beam is generally applied in the direction of a beam. But, that KB from, say, a punch, isn't always applied in the same direction. In addition, there tends to be an upward component to applied KB whose exactly nature I can't be sure about, but I assume is there because it's cooler in the game when characters get knocked through the air rather than just roll along the ground when they are hit.

Anyway, that's sort of what's going on. You can't take the number you see in the powers dialog and know exactly how far the power will send a target, because it depends on the mass of the target, the direction of the attack, etc. The number you see there is a measure of how much impulse the attack will apply and what happens after that is an issue of physics.

[vortex]

Thank you for the response, stumpy!  I was hoping there would be some specific knowable formula, but your answer was helpful nonetheless.

[stumpy]

Glad to help. I think that what IG has done there is pretty sensible, from a realism standpoint. You get to choose a measure of how much force an attack will have, then how that moves an opponent around depends on the appropriate physics (basically). If they had said something like "a (power creation dialog) KB of 20 will throw the target back 20 feet" then it would be sort of ridiculous, since it would toss a character like Liberty Lad the same distance that it would a car or even Mr. Mechanical.