Hello everyone,

in interest of full disclosure, I'm a complete ‘Fluids newbie’. Please bear with me as I attempt to get my bearings.

I'm attempting to construct my own dops fluid solver out of existing microsolvers, and running into some confusion that I could really use a hand on… At the moment it does nothing more then ‘get collided’ with a staticobject, inherits it's velocity and advects it around the vel field.

In the attached hip file are two object, identical in everyway, except the inclusion of a Project Non Divergent microsolver.

From observation I've noticed that including the PND microsolver seems to allow particles into the interior of the collision object by way of the velocity field (you can confirm this by looking through cam1 with the ‘with_projectnondivergent’ visible and tumbling the viewport). Conversely, the ‘without_projectnondivergent’ object does not.

The particles positions are being advected by the velocity field, which leads me to believe that at some point during the evaluation, the velocity field points towards the interior of the collision object (could they possibly endup inside the collision object in some other way?). This seems strange to me.

This brings to mind a few questions:

(1) Is this the expected behaviour?
(2) If it is, how do I ensure that the velocity field does NOT allow such things to happen?
(3) What is the order of operations in which these micro solvers evaluate?
(I've noticed a ‘primary solver’ field on the gas_substep dop, but based on the existing microsolvers in my scene, i'm not noticing any difference in the final output – am I missing something?)

That's it for now. Hope someone with a little bit more experience in the subject can shed some light on this…

Best,

G