matte to mask direct light shadow without losing contact shadows?

[bKittsARC]

We have a completed animation and we want to go back and composite people into the shot. (Using AXYZ's anima plugin)

If I use the VrayShadow, or VrayMatteShadow render element from the original animation sequence I can use it to mask out the existing shadows so that when the people walk into a shadow cast by a building it masks their direct light shadow. But the problem is then I lose their GI contact shadow as well.
So the question is how can I setup my comp so that when the people pass into the shadow of the direct light their own matte shadow won't show up, but their GI contact shadow remains?

thanks in advance.

[joconnell]

One way I've done this is by rendering a different setup for the shadows - I turn off gi, use a normal shadow pass element so I get the direct shadows, then also use a vray extratex element with a vray dirt map to give me ambient occlusion as a totally separate render element. It might not be 100% accurate to the gi but it's one way of separating the two shadow elements for comping.