[Plane]

Cinematic techniques are all usable (example: dual-weapon attack, roll with blow) it's just that buying them up isn't allowed except in cinematic campaigns.

In terms of perceiving the difference of a foe doing a "he's trying to walk through me as if I weren't there" (which could totally be a non-attack thing that might happen to an invisible guy, for example, or if the walker was blind) versus "he's trying to slam me", I guess one of the bigger factors would be the randomness of it.

Slams, even if they are targeting a random hit location of opportunity, are presumably done with a non-random part of the body with non-random angles and non-random timing, to best inflict damage and best avoid taking damage while inflicting it.

That's why with an accidental collision, not only should it always do less damage than a defensive attack, and be less accurate than a Committed Attack (which can suffer a -2 to hit if you take an extra step, which is the worst possible, since the -4 for Move and Attack doesn't apply to slams) but also maybe should have a higher chance of inflicting injury to the "attacker" than an intentional slam.

The main problem there is... while intentional slams can do more damage than accidental ones (in baseline this is due to being able to take AOA:strong +2 bonus) the actual damage taken by the slammer doesn't appear to be different.

To represent that, maybe those who intentionally slam should somehow take less damage, like say when rolling what they take, apply a penalty similar to "defensive attack" to the dice of damage based on the HP of the person they hit?

That allows us to use the baseline collision damages unmodified, and also to make intentional slams a little more attractive, as presently they aren't, since it requires risking taking damage unless you are using a shield (Shield Rush) as a buffer to take it instead, or are wearing armor.

Another way to represent that might be to have "attack" slams specify the body part, while "non-attack" slams would always have to be rolled on a random hit location. But that's not always going to result in a difference.

Do you know if there are any "playing chicken" rules for driving that could be consulted here? It seems like a similar concept. Like you might only be walking into someone hoping that they will blink first and move out of the way ("I won't Evade... will you Obstruct?") and if perceiving the opponent isn't reacting to this (Bluffing?) a dodge/parry might be appropriate?