Hi, There are some undocumented parameters on the Dop node - Gas Particle Move to Iso:

-Reflect Around Goal Iso
-Remove Normal Velocity (with optional attribute or field)

What do they do?

josh3light
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What do they do?

Reflect Around Goal Iso - in lamer terms it mirrors the point position using the resolved ISO position/normal as a mirror plane

Remove Normal Velocity - removes portion of the velocity that is parallel to direction of the resolved ISO normal from specified Velocity Attribute
in other words it projects point velocity to plane defined by resolved ISO normal
it can as well inherit the velocity from specified Velocity Field as if it was collision velocity

I see, thank you very much.