Houdini Resources

Updated on Sept 1  2022


copyright © Deborah R. Fowler

Fluids - Pyro

Deborah R. Fowler



Fluids - Pyro

Posted: 2013
Updated: Oct 16  2022


H18.5 also introduces the Minimal Solver (released Oct 20, 2020) timestamp 1:39:37

gpu explosion on the new shelf tool. New workflow with pyro burst tool, pyro trail on sop level.

Materials related to the new tools:

Check out SideFX new pyro workflows in Houdini 18.5 here


See also Classic (legacy) Pyro, Sparse Pyro and Pyro Tips

Sparse pyro is now recommended with the classic pyro (legacy) hidden from the shelf tool


MISSING IMAGE

In order to understand pyro, it is helpful to have an understanding of what happens during combustion.
Fuel, a source of heat and oxygen are required. When combustion occurs "exhausts" are created and heat is released (as well as light). To control or stop the combustion you manipulate the fuel available, oxygen available or source of heat. Fuel can be wood, fossil fuels (coal, oil, natural gas), hydrogen and so on.

Fuel + oxygen + heat ---> energy (heat,light,sound) + waste
combustion that is very fast explodes (rockets, car engines). Fire releases energy slowly, explosion is nearly instantaneous.

Okay, so how does this interpret into CG speak. General terms here, for specifics see the sections on specific types above.
Fuel --> flames (heat)  smoke (density) temperature (temperature) expansion (divergence)

Going one step further, interpreting it into houdini:

REFERENCE, REFERENCE, REFERENCE - ensure you find a reference for the type of fire/explosion you are trying to emulate
Study - what is the source? Is there wind? gravity? what is burning (materials)? What is the behavior - much like particles it is behavior and rendering

DO NOT use CG work as a reference! That is someone else's interpretation. This is true for all your references, not just pyro.


Houdini specific

H18 Documentation on Pyro

What is new:

  • H18 - SPARSE VOLUMES - there now exists a shelf tool for Sparse Pyro Effects
  • Sops pyro is the sparse version
  • SPARSE does not work with OpenCL - but sparse is more efficient
  • H17: Sourcing for pyro changed. https://www.sidefx.com/forum/topic/58467/
  • Now Pyro is sourcing volume from points
  • so if you are dealing with geometry brought in from an alembic be sure to unpack it.

Other Resources
Some cool tutorials

More in-depth reading

Rob Bridson, co-founder of Exotic Matter (creators of Naiad) from UBC, has some excellent references on the underlying equations controlling fluids for computer graphics. Many of the references are to Siggraph 2006 and 2007 courses as well as his co-authored book on Fluid Simulation for Computer Graphics. I would suggest to start by looking at the course notes.