In Houdini 18 the Pyro system has been greatly changed into a new system: Sparse Pyro, while the previous is marked as “Legacy”, which means you should use sparse pyro as much as you can whenever “pyro” is needed.
Aside from its “sparse” nature, the combustion model is simplified:
- In old pyro, it’s combustion model takes cares of all the fuel, burn, heat, temperature fields. All in one, but possibly confuses people.
- The new sparse pyro cut the fuel and burn off its duty. Instead, the user cope these two fields by himself/herself.
By this way the new pyro solver is greatly simplified and even better: potentially sped up. Imagine the case of a simple camp fire where a emissive flame is all you need, you can simply generate a source with only one volume, and let it be the source of flame and temperature, that’s it! No fuel, no density, no burn is calculated, couldn’t be faster!
Along with this change, one may be asking what to do in the case of fuel is required. Houdini 18 shipped some premade shelf tool or node such as Pyro Source Spread which is very handy to make the effect of gas get ignited along a rope.
And of course, diving into the rig of “Sparse Fireball” and other shelf preset is a good way to get familiar with the new way, as suggested by Houdini Doc.
Let’s go into the details.
The downside though, is you cannot make dynamical ignition easily like legacy pyro node (The temperature diffusion method used in Pyro Source Spread is quite simple and there’s no real flame).