i haven’t rendered an animation with vray a long time ago and now got some problems with precalced irradiancemap on an hemispheric sky geometry.
i now my settings might be a bit low but isn’t there a possibility to avoid these black marks where the irradiance map doesn’t have enough information, and why are these marks smaller even if the irradiancemap isn’t that detailed (calculated every 4. frame)???
It does not make sense to use the multiframe incremental mode together with the “Use camera path” option for a fly-through animation.
(*) Either use “Multiframe incremental” mode with “Use camera path” OFF, and render every Nth frame OR
(*) Calculate the irradiance map in “Single frame” mode with “Use camera path” ON for just one frame - that one map will contain information for the entire camera animation.
Best regards,
Vlado
that seems to make sense 
!!! thx very much for the fast reply vlado :-)!
With this option on will V-ray calculate the IR map for every frame? Isn’t the first option faster then?
No, because you only do it for one frame, you don’t render the animation.
Best regards,
Vlado
edit:
Has the multiframe incremental mode become obsolete
Not quite; the “Use camera path” option is only useful for short camera paths; if you have a long fly-through, then the classic method with Multiframe incremental is still better.
Best regards,
Vlado