[Sidefx-houdini-list] Building a particle collision system

Rangi Sutton rangi.sutton at gmail.com
Sun Aug 15 19:07:55 EDT 2010

On 16 August 2010 08:56, Alex Czetwertynski <alex at franktheplumber.com>wrote:

> Out of curiosity, why would using an SDF volume be better for collisions?

There's no need for a collision detection stage... you sample the SDF at the
particles position, its sign tells you if it's  inside the oject (negative),
or outside. The value tells you how far, and the gradient gives you
(effectively) the surface normal. Good info for bouncing/sliding particles.

So the hit is in calculating the SDF.. the saving is every particle sampling
against that... so you get more speed benefit the more particles.

This can be implemented really simply in vops. And the SDFs, once you've got
them in your scene, turn out to be pretty useful for loads of other stuff as


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