Game Development Reference

In-Depth Information

F
IGURE
14.1

The rotational and linear components of a collision.

given by

1

m
f

p

=

¨

and the angular component by the torque

τ

=

p
f
×

f

where the torque generates angular acceleration by

θ

I
−
1
τ

=

which is equation 10.3 from chapter 10.

In the case of the collision it stands to reason that the collision will generate a

linear change in velocity (the impulse) and an angular change in velocity. An instan-

taneous angular change in velocity is called an “impulsive torque” (also rarely called

“moment of impulse” or “impulsive moment,” which sounds more like a drunken

Vegas wedding to me).
1

Inthesamewayaswehave

I
θ

τ

=

for torques we have

I
θ

u

=

1.
Strictly speaking, what we've called impulse is “impulsive force.” We could also call it “linear and an-

gular impulse,” but I'll continue to use just “impulse” to refer to the linear version.