Knockback

[Skarg]

Several times, in threads discussing GURPS Knockback, it's been said that Knockback would not really happen because of physics concepts such as equal and opposite counter-reactions, and force applied versus the mass of a human body. It seems to me that people can and do tend to fly about when rough-housing, not even being seriously injured. It tends not to be that someone is throwing their entire mass through the air, but that they get put off balance and end up doing something like stumbling backwards, often fairly quickly.

That said, I also think the association with damage points is unrealistically linked, because people can send each other flying several yards without actually seriously injuring them.

See for example this: http://i.imgur.com/ugN7Ta3.webm. The first may be some sort of Push attack, but the second involves a punch... the demonstrator (Bruce Lee, I believe) isn't trying to injure the target, so I suppose it's both, but I tend to think this shows that getting nailed with unarmed and hand weapon attacks can cause the target to end up even several yards back from where they started, and not necessarily based on how much damage they take. (And yes, freakin' Bruce Lee! But also, six hexes or so of knockback from a punch that probably did 1 point or less injury - the point is getting hit not-catastrophically can cause someone to stumble back quite a bit).

No?

[Gollum]

Originally Posted by Skarg

Several times, in threads discussing GURPS Knockback, it's been said that Knockback would not really happen because of physics concepts such as equal and opposite counter-reactions, and force applied versus the mass of a human body. It seems to me that people can and do tend to fly about when rough-housing, not even being seriously injured. It tends not to be that someone is throwing their entire mass through the air, but that they get put off balance and end up doing something like stumbling backwards, often fairly quickly.

That said, I also think the association with damage points is unrealistically linked, because people can send each other flying several yards without actually seriously injuring them.

See for example this: http://i.imgur.com/ugN7Ta3.webm. The first may be some sort of Push attack, but the second involves a punch... the demonstrator (Bruce Lee, I believe) isn't trying to injure the target, so I suppose it's both, but I tend to think this shows that getting nailed with unarmed and hand weapon attacks can cause the target to end up even several yards back from where they started, and not necessarily based on how much damage they take. (And yes, freakin' Bruce Lee! But also, six hexes or so of knockback from a punch that probably did 1 point or less injury - the point is getting hit not-catastrophically can cause someone to stumble back quite a bit).

No?

In that video, the attacker is not really trying to injure his opponent, which makes a huge difference with an ordinary attack: he is precisely demonstrating how far he can make move the opponent backward with a punch. Also note that the stance of the opponent is not a combat one. He is just standing normally and, so, very easy to destabilize. By the way, if you look more closely to the video, you will note that the opponent actually falls backward just before going backward (sometimes by making some steps by himself!). He is at minimum as thrown of balance as pushed backward ...

Having said that, the attacker is still very skilled and I wouldn't like to take one of his punch with a true intention of hurting!

Furthermore, I don't have any problem with Knockback rules. I admit that in reality, the knockback power is more dependent on the type of attack than the amount of damage (a car slam obviously makes move backward much more than a mace strike, which makes move backward much more than a blade slash, and so on). The surface of the hurting object sound to be as important as its speed. But it would inevitably lead to too much complicated rules ...

That is why the knockback rule as written perfectly fits to my games. In GURPS, a truck slam usually inflicts much more damage than a punch and so, has much more chance to knockback the character.

[Tomsdad]

Originally Posted by Skarg

Several times, in threads discussing GURPS Knockback, it's been said that Knockback would not really happen because of physics concepts such as equal and opposite counter-reactions, and force applied versus the mass of a human body. It seems to me that people can and do tend to fly about when rough-housing, not even being seriously injured. It tends not to be that someone is throwing their entire mass through the air, but that they get put off balance and end up doing something like stumbling backwards, often fairly quickly.

That said, I also think the association with damage points is unrealistically linked, because people can send each other flying several yards without actually seriously injuring them.

See for example this: http://i.imgur.com/ugN7Ta3.webm. The first may be some sort of Push attack, but the second involves a punch... the demonstrator (Bruce Lee, I believe) isn't trying to injure the target, so I suppose it's both, but I tend to think this shows that getting nailed with unarmed and hand weapon attacks can cause the target to end up even several yards back from where they started, and not necessarily based on how much damage they take. (And yes, freakin' Bruce Lee! But also, six hexes or so of knockback from a punch that probably did 1 point or less injury - the point is getting hit not-catastrophically can cause someone to stumble back quite a bit).

No?

Most of that backward movement (especially in the second one) is due to the chair and the floor not having an awful lot of friction.

Also the target doesn't exactly look like they are set in a combat stance (quite the opposite both look like they are about to topple backwards before being punched, lets be polite* and call it anticipation of the hit)

[Gollum]

Originally Posted by Tomsdad

Also the target doesn't exactly look like they are set in a combat stance (quite the opposite both look like they are about to topple backwards before being punched, lets be polite* and call it anticipation of the hit)

It can work even without that anticipation. In our karate, we've got a technique that makes the opponent "fly" 2 to 3 yards backward before falling. You just have to strike him to the hip bones with the two open hands at the same time (a few inches under the center of gravity). But it doesn't really hurt. So, the opponent just falls down and then, if he is a bit trained, can stand up before you attack him again. It is a make fall technique, not a true attack ...

Note by the way that, in reality, the knockback effect also depends on where the blow exactly strikes. A few inches can make a huge difference.

[Tomsdad]

Originally Posted by Gollum

It can work even without that anticipation. In our karate, we've got a technique that makes the opponent "fly" 2 to 3 yards backward before falling. You just have to strike him to the hip bones with the two open hands at the same time (a few inches under the center of gravity). But it doesn't really hurt. So, the opponent just falls down and then, if he is a bit trained, can stand up before you attack him again. It is a make fall technique, not a true attack ...

Note by the way that, in reality, the knockback effect also depends on where the blow exactly strikes. A few inches can make a huge difference.

Ok, but what you describes kind of makes my point about footing. If you have been able to approach me and strike either side of my pelvis with both hands, I have truly messed up my footing/stance! Also if my pelvis is significantly below my centre of gravity I've messed up my stance again (it sounds like I'm standing up straight as well as straight on to you). Leaving aside the issue that I somehow let you get that close to me in what I'm assuming to be quite an awkward stance of your own. (Unless your crouching with your shoulders level with my pelvis you'll be largely pushing me down, not back let alone up)

I'll be honest I never seen a strike like you describe*, but I'd have thought that if you're pushing below my centre of gravity I'm as likely to fall forward as backwards, and "flying 2-3 yards back"? Are you describing stumbling two or three yards back? Flying 2-3 yards back before falling is going to hurt.

IME getting someone's feet to leave the ground tends to require pivoting their mass over/around something** (but that might just be my judo background colouring my perception)!

But as I say I've not seen what your describing so can't really judge the reality of it compared to the picture of it in my mind.



*but it's not like I have a full and encyclopaedic knowledge of all martial arts moves in the world!

edit: Actually the closet I've seen is someone from prone kicking up with both feet to the pelvis of a standing opponent.


**Well OK barring physically lifting them off their feet!

[Anaraxes]

Originally Posted by Skarg

it's been said that Knockback would not really happen because of physics concepts such as equal and opposite counter-reactions

I've seen this comment applied to bullets, especially the Hollywood action scene where someone gets shot and gets flung backwards, off the floor, limbs spread, though a window or such. A bullet doesn't carry that much momentum, and if it did, then yes, it would push back just as much on the firer when it starts moving as on the target when it stops.

However, that's not the same thing as pushing someone off-balance and making them stumble backwards.

In the linked video, most of the force isn't coming from Bruce Lee. It's gravity. The chair actually amplifies the effect as it takes the subject off their feet and converts even more of their height above the ground to backwards motion as they rotate around their last foot position toward the chair. Since Bruce isn't supplying all that force, Bruce doesn't get pushed back as much as the subjects do.

[Gollum]

Originally Posted by Tomsdad

Ok, but what you describes kind of makes my point about footing. If you have been able to approach me and strike either side of my pelvis with both hands, I have truly messed up my footing/stance!

OK. But to my point of view, you put too many different things in the word "stance" here. As I understand it, the stance, or "having a good footing" (dachi in Japanese) is different from the combat distance (ma or mai) and from the fact of moving (ashi).

Now, I'm French and I may completely misunderstood the subtleties of the English word "stance".

Originally Posted by Tomsdad

Also if my pelvis is significantly below my centre of gravity I've messed up my stance again (it sounds like I'm standing up straight as well as straight on to you).

To make the technique I am talking about, you have to strike just under the center of gravity. A bit under. Like I said, it is a matter of few inches. The purpose is to unbalance the opponent as effectively as you can and if you strike above the center of gravity, the opponent weight will be harder to move and make fall.

Originally Posted by Tomsdad

Leaving aside the issue that I somehow let you get that close to me in what I'm assuming to be quite an awkward stance of your own. (Unless your crouching with your shoulders level with my pelvis you'll be largely pushing me down, not back let alone up)

To do this technique, the attacker has to lower his body, indeed. The Shikodachi posture is the best one.

http://zhkarate.com/wp-content/uploa...Shikodachi.jpg

The strike is done with morote shotei (two shotei at the same time), one at each side of pelvis.

http://www.seishin.lt/lib/manage/upl...-%20Shotei.gif

And, of course, it has to be done against someone who has higher posture like most usual fighting posture for instance.

Furthermore, never try that when the attacker is ready to avoid it easily! Do it immediately after parrying a jodan tstuki (punch at the face) for instance. You will add a surprise effect to your technique. And don't forget that it makes go backward and fall, but that it doesn't hurt more than that. You won't ever brake any bone with this technique, unless having a lot of luck (if the opponent hurt himself while falling down). So, in most cases, a good punch or kick is a much better option for self-defense!

Like I tried to say it above, making someone knockback or hurting him are two very different things*. Which is quite well reflected in GURPS. Since a bare handed character rarely inflicts 8 points of damage or more, he rarely knockbacks his foe.

_____

* I would even consider that like a GURPS-"Judo"-skill technique rather than a GURPS-"Karate"-skill technique. Or, even better, a GURPS-"Sumo"-Wrestling-skill technique.

[Skarg]

Originally Posted by Gollum

Like I tried to say it above, making someone knockback or hurting him are two very different things*. Which is quite well reflected in GURPS. Since a bare handed character rarely inflicts 8 points of damage or more, he rarely knockbacks his foe.

Generally true, although with Karate damage bonus, kicking, boots, converting +3 to +1d, and possibly All Out for +2 damage, the odds of doing 8 can get pretty high. I don't think the problems is the amount or frequency of knockback per se (except for bullets and silly numbers with high-tech DR/weapons), but rather the predictability of whether it will or won't happen, because as people keep saying, a target going backwards isn't really about throwing them with direct brute force. Real targets going backwards seems to be much more about the target ending up going backwards due to tipping, lack of resistance, stumbling, flinching, etc., none of which are very predictable from the usual level of detail at which we play. That is, ideally/realistically (for those willing to handle another mechanic) it seems like an independent chance, which wouldn't really be linked only to the damage roll.

There are ways to throw people around in GURPS other than knockback, of course, but (for those of us who care enough) it seems like what's missing is a less predictable random chance of targets falling back, not linked to 8 points of damage (which has unarmored people needing to be nearly battered unconscious in one blow before they'll stumble back, as well as everyone battered that hard always falling back, neither of which seems right).

[Koningkrush]

http://forums.sjgames.com/showthread.php?t=135940

This is a thread from a while back talking about knockback, with a couple house rules here and there.

In the end, I decided to just use logic and roleplay it based on the situation.

If knockback damage came from something like a mace hit, just describe it as stumbling backwards from a massive blow. If the mace happens to be the size of a car, then describe it as the person flying through the air.

This is something that causes too much headache to simulate. Nothing short of a full physics engine running in a simulation program will be able to handle things that specific. So, use the best computer in the world for simulating things, that being your brain and your imagination. In the end, it doesn't change anything; the mechanics are still the same.

[Anthony]

There is no question that it is possible to knock someone down with an attack, and a person who is off balance or falling over can move some distance. However, the concept 'knockback' usually implies that it's the attack itself moving the target, and that's basically a nonissue outside of slam attacks.