function lerp(a, b, t, dst) {
    dst = dst || new VecType(3);

    dst[0] = (1 - t) * a[0] + t * b[0];
    dst[1] = (1 - t) * a[1] + t * b[1];
    dst[2] = (1 - t) * a[2] + t * b[2];

    return dst;
  }
Performs linear interpolation on two vectors.
Given vectors a and b and interpolation coefficient t, returns
(1 - t) * a + t * b.
@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..
@memberOf module:twgl/v3