Game Physics Engine Development, 2nd Edition

3

The Laws of

Motion

hysics engines are based on Newton’s la ws of motion. In later sections, we will

Pbegin to use results that were added to Newton’s original work, but the funda-

mentals are his.

Newton discov ered three laws of motion that describe with great accuracy how

point masses behave. A point mass is somewhat imaginary: it is an object that has

mass, but no size. It is an object, therefore, that can’t rotate, but otherwise moves

ar ound normally. It might seem that this fantasy is particularly useless: every real

object does have size, after all. But the physics of many things can be simplified to

point masses. Newton used his laws very succe ...