Residue of shadow from ir map

[nigelwilliams]

Dear all

This one is getting beyond me. I am rendering an animated scene, using a premanufactured ir and lc map, as opposed to making a new one of both every time. The scene has 1 off vray sun, and I can render quite quickly but here is the problem.
When the upper part of the building has moved away its shadow remains, or what appears to be a part of it. whereas if on the indirect illumination tab, the IR map and the light cache are both set to single frame then this will not occur. No there was not a fire ino the basement!, just looks like it

The ir map is made using the multiframe incremental mode and the light cache is made in fly through mode,

[percydaman]

You seemed to answer your own question. You can't use multiframe incremental for doing animations where objects or lights move. It takes the previous irradiance map, and adds the current one on top of it, instead of discarding the previous and creating a new one, hence your shadows stick around.