Drive opacity by object distance? Or animated Ramp in space?

[BeneZ]

Hello,

for an object transition I would like to use an animated alpha.

(The same object is there in two versions)

- I think I have seen, that an object (a sphere for example) can drive the alpha.
But I can't remember exactly how that worked.

Any help appreciated

[hermit.crab]

A Gradient Ramp mapped with VRayDistanceTex that drives the opacity color of a VRayMtl should work.