yes thank you
this is what i exactly did
i reduced all other materials opacity to 0%
separate the object on different layer
and the problem solved
although it took the same amount of rendering time as rendering the whole scene,
i thought it will take less time, because i am rendering only the wanted ...

what i mean is, if i have object with several material on it, and i want to render only one material of them as a separate pass.
is it possible, if not possible with Lightwave3D, then how to do it with the stand alone version.?

thank you

Is it possible for octane to render inly one specific material. Without rendering the whole scene?. As this should save me alot of precious time