LogInSergey Kharitonov shared some tips and released a setup for purchase.
Sergey Kharitonov, whose work on small-scale liquid simulations we've featured before, has presented a new water simulation setup and shared insights into his approach.
Adding water droplets to close-up renders is a popular technique for boosting visual interest and making objects appear more dynamic and detailed. While creating static droplets on a surface is relatively straightforward, even for beginners, animating them to move realistically across surfaces is a much more complex challenge.
As Sergey mentioned, he personally considers two existing methods to be among the most realistic: a procedural tool developed by José Mauro Lobão and an X-Particles rig for Cinema4D created by Sam Tato. There's also a built-in Houdini shelf tool located under Particle Fluids – Condensation, but he finds it relatively slow and difficult to control, likely due to its reliance on the FLIP solver at its core. The artist decided to take on the challenge and build a version entirely from scratch. Here’s the algorithm he followed:
- Scatter droplets of varying Pscale across the object's surface;
- Select some of the droplets to animate using the POP solver;
- In the POP Network, apply forces to move the droplets downward (mainly some custom gravity, additional velocity noise, and drag);
- Ensure particles stay stuck to the surface using the volume sample and volume gradient technique;
- As the animated droplets move, they are 'eating' any static particles they encounter. This behavior is controlled by a custom algorithm written using about 40 lines of VEX code (by the way, thanks to the Houdini Hangout YouTube channel for the 5-hour stream on droplet simulations, it was very insightful);
- Moving particles clear a path and leave behind a subtle trail that could slowly evaporate over time.
Sergey has released the finalized version of his sliding droplet simulation setup for Houdini on his Gumroad page. To adapt the setup to your own project, you'll need at least a basic understanding of Houdini (intermediate-level experience is recommended). The setup is a lightweight procedural system built around a POP Solver. On Sergey's PC, it can simulate around 500 frames of multiple droplets sliding across a surface in under 30 seconds.
Sergey regularly shares Houdini tips covering a wide range of simulations, not just water, so follow him on LinkedIn for more great content:
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