calculateLocalInertia method
Calculates the inertia in the local frame for this shape. @see http://en.wikipedia.org/wiki/List_of_moments_of_inertia
Implementation
@override
Vec3 calculateLocalInertia(num mass, [Vec3? target]) {
target ??= Vec3();
double I = (2.0 * mass * radius * radius) / 5.0;
target.x = I;
target.y = I;
target.z = I;
return target;
}