Hi all, been learning Houdini since mid Feb and thought it time I better share something back as I've found the forum immensely useful ;-)
RnD of Houdini particles flowing over a hard surface model to simulate a condensation/rain/rivulet/droplet effect.
This is part of a larger RnD project I'll render & upload shortly (this is one section of a larger flying object - a cloud seeding drone... just an excuse to learn a load of Houdini).
Partly inspired by Mark Theriault's Sucker Punch Intro Breakdown using Pflow (vimeo.com/39161208) and having just starting making the switch for fx from Maya to Houdini,
this was one of those "I wonder if I can do that now in Houdini" things that I just had to try. I remember years ago doing something similar in Maya and it taking a heck of a lot longer!
This effect took about a week of tweaking.
The sim is basically just a popnet which relies on an SDF volume (isoOffset) for surface interaction and uses a voppop (VEX) to control the "drip off threshold".
Once I had a working method, I then used 3 duplicate variations for the different rivulets (trail SOP) and finally added a random scatter SOP for some extra motionless droplets.
As the final shot won't be so closeup, I have to option of increasing/decreasing the uniform sampling of the SDF to fit.
When all this is done, I'll hopefully be taking this RnD further with a rain-on-a-window-pane high-detail/realism sim.
Thanks to SpencerL for advice on the initial VEX methodology.