I'm hoping someone, even someone at SideFX can help.

I have a scene, which I can share if required. How can I have particles (POPS) effect grains or maybe the other way around, have grains effected by particles but using only a DOPNet, not the SOP vellum nodes. In other words, how to setup vellum and Particles (POP) in a DOPNet ?

The POPNet is a DOPNet and I have merged a vellum solver and a POP Solver within a POPNet (DOPNET) but it is not working ?

Also, is it possible to control vellum cloth with particles, in other words, build cloth using particles or have cloth rip away using particles ?

Here is an example that shows how to attach a vellum sheet to a particle, then when a particle dies, the constraint is deleted and the patch is free. One of the issues I found for this kind of setups when you need to attach things, is that vellum constraints nodes has no option to specify the attachment by id for example or using a matching rule, so if your points are really deleted the system will become crazy because internally is just using the ptnum for the constraint targeting. It will be nice to have matching options to do some clever targeting in a Vellum Constraint SOP or DOP.

@Alexjandro - I'm having a little problem following your network as some nodes are not evaluating ? I do understand what you mean regarding the id but as with your scene must I source the particles using a vellum source.

I've attached my scene file, I want only grains on the particles using only a DOPNet, not the newer SOP workflow using vellum.
I want to create constraints only for the orange particles. In any case I cannot get vellum grains on the particles; must I change the points to a volume then it will only work ?

Those nodes are throwing an error at the beginning because there is no data for the vellum sops to evaluate correctly, but just press play on the file and everything will work perfectly after frame 1.

If I understand this correctly, one must use a DOP I/O node to bring in the particles, then and only then can I apply vellum grain constraints ?

Although there is one thing, your setup you are not using the vellum configure grains sop and using this node to visualize the grains, you are just using copyToPoints, I'd like to see using this node ?