Dear Houdini community, I am currently working on a project where I want the geometry to grow procedurally over time. For that, I employed a Solver geometry node, and modifies my geometry in the loop, similar to this tutorial https://www.youtube.com/watch?v=NqdnTXuxn6k. [www.youtube.com]

In addition to modifying the geometry procedurally, I also wanted to run physical simulation in the loop. So for that, inside the Solver geometry node, I inserted a Vellum Solver which runs quasistatic simulation and drives my geometry in a physics-based manner. Luckily, in Houdini this works exactly as expected.

However, the issue arises when I try to add a POP Advect by Volumes node inside the Vellum solver node, in order to load an prespecified vector field as my external force for simulation. It seems there is some issue with Houdini finding the proper SOP for the vector field. In the project file attached, the test_solver geometry node can successfully run quasistatic simulation with my custom vector field. But the test_solver_inside_solver fails to do so, and the geometry disappears immediately. The only difference is that in the latter, the Vellum Solver is wrapped in another Solver, which I didn't expect to make a difference in this application.

This is my first post in this forum and my apologies for the long problem description. I am super grateful for any input on how this issue might be circumvented. Thank you all very much for your attention!