function lerp(a, b, t, dst) {
  dst = dst || new VecType(3);
  dst[0] = a[0] + t * (b[0] - a[0]);
  dst[1] = a[1] + t * (b[1] - a[1]);
  dst[2] = a[2] + t * (b[2] - a[2]);
  return dst;
}
Performs linear interpolation on two vectors.
Given vectors a and b and interpolation coefficient t, returns
a + t * (b - a).
@param {module:twgl/v3.Vec3} a Operand vector.
@param {module:twgl/v3.Vec3} b Operand vector.
@param {number} t Interpolation coefficient.
@param {module:twgl/v3.Vec3} [dst] vector to hold result. If not new one is created.
@return {module:twgl/v3.Vec3} The linear interpolated result.
@memberOf module:twgl/v3