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Old 02-12-2012, 12:51 PM   #41
vitruvian
 
Join Date: Aug 2004
Default Re: Unintentional slam suicide

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Originally Posted by trooper6 View Post
You are upset that colliding with an elephant's butt or a Giant Stone Armadillo will hurt more than running into a super-hard and absolutely-immovable stone wall. You ask if you are missing something very important. I'd say you are. Your calculations are all off.

Your calculations for that stone wall are totally off. You give the stone wall 10hp. "2*10*5/100 = 1d." Stone walls do not have 10hp. If you turn to B558, you'll see the listed hp for stone walls. Since you describe it as super-hard and absolutely-immovable, I'm going to go with the stats of an 8' wall. That's 188hp (not 10!). The calculation for that slam damage? 2*188*5/100 = 19d.

You give the elephant 50hp, B460 lists it at 45hp, but let's look at the calculations both ways. At the listed 45hp you get, 45*5/100 = 2.25d =2d. At 50hp you get, 50*5/100 =2.5d =3d. So you are looking at either 2d or 3d slam damage. *Much* less than the 19d for running into the stone wall.

So now this giant stone armadillo. It has 400hp? That means it is thicker and bigger and harder than that stone wall so it would make sense it would do more damage than the stone wall...though it only does 1d more...so they are quite equivalent. Your only hope would be that not all of that 400hp comes from mass (see Martial Arts p.49 the box on extra hit points)...but since we are talking about a Giant Stone Armadillo...it does seem like those hp represent mass.
Nope. Running into something hard and immovable maxes out at 2x your HP x velocity / 100 (B431). Otherwise, falling from a yard of height, you'd explode. That's the rule for running into walls; the HP of the wall doesn't matter for calculating max damage, although you can't actually take more than the wall's HP + DR, at which point you break through (also B431).

And that's only if it's hard, not soft. Anyway, it makes no sense for running into a high HP target that is (slightly) moveable to do more damage than running into an immoveable one, so for running into a stationary target, I always cap it at 2x your HP x velocity/100.

If a high HP object is slamming into you, though, I generally use its full HP, at least for knockback purposes. A semi ramming you at 60 mph is bringing a whole lot more kinetic energy to the table if you were running into a parked one on your motorcycle.

Last edited by vitruvian; 02-12-2012 at 01:05 PM.
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Old 02-12-2012, 12:59 PM   #42
Ze'Manel Cunha
 
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Default Re: Unintentional slam suicide

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Originally Posted by vitruvian View Post
Nope. Running into something hard and immovable is 2x your HP x 100. Otherwise, falling from a yard of height, you'd explode.
Somebody has to send that in as a Murphy, guy running down the street gets distracted as someone calls him and Slams into the side of a Godzilla's foot, exploding on contact...
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Old 02-12-2012, 01:06 PM   #43
vitruvian
 
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Default Re: Unintentional slam suicide

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Originally Posted by Litvyak View Post
I'm not your GM, but based on your description and my reading of the RAW regarding collisions, I would have ruled the damage you received as follows: He wasn't moving, so his velocity was 0... HPx0/100 = 0 which is less than 0.25 making the damage taken by your character 1d-3. However, if the monster was so large as to count as an immovable object, you would have received the same amount of damage that you dealt.
By RAW, it's relative velocity, not each object's own velocity - although as already stated, I would cap nevertheless cap damage if the larger object is stationary. Your way of doing things, though, would result in not taking damage from falling, since the Earth is at Move 0.
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Old 02-12-2012, 01:13 PM   #44
Silhouette
 
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Default Re: Unintentional slam suicide

I like the idea that damage should be proportional to self HP and difference of self velocity before and after collision.

So I made some calculations:

If there are two rigid bodies with a mass m1 and m2, and they are colliding with a relative speed Vr, then after collision, velocity of the first object will change by:

dV1 = 2 * Vr * m2 / (m1 + m2)
or if we assume that we can replace mass with HP
dV1 = 2 * Vr * HP2 / (HP1 + HP2)

And for second object:

dV2 = 2 * Vr * m1 / (m1 + m2).
or
dV2 = 2 * Vr * HP1 / (HP1 + HP2).

In extreme case, when m2 → ∞ (for example, it's an Earth),
dV1 → 2 * Vr.
Body will bounce back. Ok.

In this case, Basic Rules says that damage will be 2*[Self HP]*velocity/100 (for hard object), so, if formula should look something like k*HP*dV, then It probably should be:

Damage1 = 2 * HP1 * (Vr * HP2 / (HP1 + HP2)) / 100
(when HP2 → ∞, Damage1 → 2 * HP1 * Vr / 100, exactly as in RAW rules)

Damage2 = 2 * HP2 * (Vr * HP1 / (HP1 + HP2)) / 100
(when HP1 → ∞, Damage2 → 2 * HP2 * Vr / 100, exactly as in RAW rules)

In fact, Damage1 = Damage2 = 2*Vr*(HP2*HP2)/(HP1 + HP2) / 100 (in dices) for hard bodies.

For soft bodies we can divide mutual damage by 2.

Example1: Two 10HP people collide at relative speed 10.
Damage = 2*10*10*10/(10+10)/100 = 1d (for hard collision), or 0.5d for soft.

Example2: 20HP brute collides with 8 HP kid at relative speed 6.
Damage = 2*6*20*8/(20+8)/100 = 0.68d (for hard collision), or 0.34d for soft. So your kid won't explode after running into you happily at full speed.

Example3: 20HP brute collides with 1 HP tennis ball at relative speed 5.
Damage = 2*5*20*1/(20+1)/100 = 0.095d, because ball will just bounce away, not EXPLODE or anything like that.

Example4: 10HP character collides with 400HP Giant Stone Armadillo at relative speed 5.
Damage = 2*5*10*400/(400+10)/100 = 0.97d. Slightly softer than a brick wall. For Giant Duckling it will be only 0.48d.

Bad thing - formula became more complex.
Good thing - we need only one calculation for both bodies.

How do you think, is that a viable idea to calculate slam damage like this?
How would you fix rules for KO to be realistic?

Last edited by Silhouette; 02-12-2012 at 01:19 PM.
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Old 02-12-2012, 01:16 PM   #45
Litvyak
 
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Default Re: Unintentional slam suicide

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Originally Posted by vitruvian View Post
By RAW, it's relative velocity, not each object's own velocity - although as already stated, I would cap nevertheless cap damage if the larger object is stationary. Your way of doing things, though, would result in not taking damage from falling, since the Earth is at Move 0.
Where does it say that? I'm looking at B430 "Damage From Collisions" and there is no mention of relative velocity.
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Old 02-12-2012, 01:30 PM   #46
Refplace
 
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Default Re: Unintentional slam suicide

The slam thing comes up often enough hat it really should be in the FAQ but I just checked and did not see it there.
There was a long thread on it just a few months ago.
I think the consensus was each person takes damage based on their HP.
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Old 02-12-2012, 01:37 PM   #47
vitruvian
 
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Default Re: Unintentional slam suicide

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Originally Posted by Litvyak View Post
Where does it say that? I'm looking at B430 "Damage From Collisions" and there is no mention of relative velocity.
B371. Also implied by B431, since if not, you would take no damage from falls or running into walls, ever, since they didn't move, only you did.
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Old 02-12-2012, 01:40 PM   #48
Ts_
 
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Default Re: Unintentional slam suicide

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Originally Posted by Refplace View Post
The slam thing comes up often enough hat it really should be in the FAQ but I just checked and did not see it there.
Definitely.

Quote:
Originally Posted by Refplace View Post
There was a long thread on it just a few months ago. I think the consensus was each person takes damage based on their HP.
Don't remember if that was the consensus, but it seems weird: With that rule, suicide flies could easily kill elephants through slams. Or if you throw something at the ground really hard, the earth takes damage proportional to its HP ...

Really, the lower of the two HP is the best guideline for damage to avoid all this nonsense. And the Spaceship fix (larger HP counts only up to twice the lower HP) still leaves some wiggling room to exploit in favor of the larger slammer.

Regards
Ts
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Old 02-12-2012, 02:00 PM   #49
vitruvian
 
Join Date: Aug 2004
Default Re: Unintentional slam suicide

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Originally Posted by Ts_ View Post
Definitely.


Don't remember if that was the consensus, but it seems weird: With that rule, suicide flies could easily kill elephants through slams. Or if you throw something at the ground really hard, the earth takes damage proportional to its HP ...

Really, the lower of the two HP is the best guideline for damage to avoid all this nonsense. And the Spaceship fix (larger HP counts only up to twice the lower HP) still leaves some wiggling room to exploit in favor of the larger slammer.

Regards
Ts
Lower of the two, with up to twice the smaller party's HP counting as for immovable objects, works well, at least when it's the smaller object actually slamming into a stationary larger one.

If the larger object is actually the one doing the slamming, though, I'd probably use its full HP, at the very least for knockback purposes if not actual damage inflicted. A semi ought to be able to knock a pedestrian out of their shoes and across the road, and further than a compact car would.

For simplicity's sake, I'd probably run this one of two ways:

1) If I've got convenient numbers of differently colored dice available, calculate both full (larger HP x velocity/100) and capped (2 x smaller HP x velocity/100) damage, and use red dice or something for the capped damage and white dice for the remainder. Whole damage counts towards knockback, only red dice count towards injury. But even that's a bit finicky, so

2) Roll all the dice, but cap injury at (12 x smaller HP x velocity/100 in HP of damage - roughly the maximum that could have been rolled on the smaller amount of dice)
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Old 02-12-2012, 02:03 PM   #50
Litvyak
 
Join Date: May 2007
Default Re: Unintentional slam suicide

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Originally Posted by vitruvian View Post
B371. Also implied by B431, since if not, you would take no damage from falls or running into walls, ever, since they didn't move, only you did.
Ah.. I hadn't realized that slam used a different wording for the rules. Cool. I'd just use the rules for collision angle (side on collision) on B432: "The struck object cannot inflict more dice of damage than the striking or falling one."
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