For an ideal diode:
the ON state can be treated as short circuit.
the OFF state can be treated as open circuit.
The following java applet simulate a two level clipping circuit.
Click at one of the voltage source (DC or AC) to change its amplitude.
Left Click at hold down : decrease its value continuouslyRight Click mouse button to toggle the animation.
Right Click at hold down : increase its value continuously
You can also enter new value into the TextField (Double click mouse button )
Left waveform is input signal , the right one is the output signal
Red dots shows the amplitude at that time.
Yellow dots on the circuit show the flow of the current.