Okay, hopefully I can adequately explain the scenario that is puzzling me. I have a SOP node that generates geometry. It takes no inputs, and therefore is a pure generator. It assumes that unless certain internal conditions are met, that the geometry it generated during its last cook is still in the Detail when it cooks again.

However, this is not always the case. For instance, if the user toggles the bypass flag, Houdini will clear out the geometry that is cached in my node. I can detect this by implementing SOP_Node::bypassMe(). However, I also notice that if I attach a TimeShift SOP after my generator SOP and put the display flag on it, my SOP's geometry gets wiped out from underneath it.

If there is a virtual function like bypassMe() that is called when Houdini goes and does this, I'd love to know about it so that I can update my SOP's internal state flags and force it to regenerate its geometry on the next cook. So my question is two-fold:

(1) What is going on when Houdini encounters a TimeShift in the network chain? I mean, aside from passing an appropriately time-shifted context to my SOP, what else is going on behind the scenes that I need to know about?

(2) Is there a virtual callback function (like bypassMe) that I can implement in my SOP to detect that the Detail has been wiped out?