Hi, Im writing a SOP node (HDK 10) to perform some basic particle simulation and need to connect a volumetric force field. From what I understand, one way to do this is to define the force field at DOP level and then do a DOP import fields. If I connect a gravity force node to a vector field and then try to import it, it won't work. Do I need to drive a simulation to get any values - with a solver and so on?

If this does not work at all I will try to use a Volume VOP to define the force field. But the Volume VOP will only take a scalar Volume, are there any way to make it work on 3d vectors? Any other ideas on how to do this as convenient as possible?

Volume primitives are always scalar. To work with fields greater than 1 dimension, you need to create multiple Volume primitives. You can then group them together (eg. see Name SOP).

At the SOP level, you just need to access the Volume primitives in your custom SOP. eg. via another input. To import geometry data from DOPs, you can just use an Object Merge SOP with some special node path syntax (see the helpcard).