function motionblur(target, persistence) {
    return new MotionBlurLoop(target, expr_1.wrapInValue(persistence));
}
creates a frame averaging motion blur effect
@param target the channel where your accumulation buffer is (defaults to 0,
which you might be using for something like the depth texture, so be sure to
change this to suit your needs)
@param persistence close to 0 is more ghostly, and close to 1 is nearly no
motion blur at all (defaults to 0.3)