fading on/off led lighting

I'm installing ambient led lighting under kitchen cupboards & plinths using 12v led strips & almost finished but just at last minute have decided i'd like to make them fade on and off - from my older electronics days i presume its doable with a capacitor and resistor - for example the plinth lighting will be 12v 500ma. Under cupboard 12v 700 ma both seperately switched on/off any one got help re calculations of capacitors etc I know i'll need resistors that handle 6watts+

of course any ideas on a different way to do it appreciated

Fading on/off might mean for the LEDs to brighten slowly for a couple of seconds when they are turned on then they dim alowly for a couple of seconds when they turn are turned off?

You might be able to do it with a huge capacitor and two resistors.
Usually it is done with a small capacitor and a resistor that drive a darlington transistor.

How are the LEDs and their current-limiting resistors wired so that they can use 12V?