Point Light shadow map using a single 2D texture

Hi all,

I'm trying to make shadow maps for point lights and I want to use just a single 2D texture for storing the shadow maps for all of the 6 faces (as I render it with 6 90 deg cameras).
However I need to be able to sample this 2D texture as if it was a CUBE map, just by using a float3 for the sampling direction.

Is there a smart way to layout my shadow maps and a smart computation where I can convert the float3 sampling direction to float2 UV for sampling? My solution has too …