Tuesday, May 18th, 2021 Posted by Jim Thacker

Check out neat free Houdini sparse GPU fluid solver Axiom

Originally posted on 14 January 2021. Scroll down for news of Axiom Build 6.

Former ILM FX TD Matt Puchala has updated Axiom, his neat free GPU-accelerated sparse gaseous fluid solver for Houdini, intended to provide a faster alternative to Houdini’s own Sparse Pyro solver for look dev.

Build 4 of Axiom supports colour sourcing, making it possible for users to simulate coloured smoke.

A faster alternative to Houdini’s spare Pyro solver for look development
First released last fall, Axiom is a GPU-accelerated sparse gaseous fluid solver.

Like the native Sparse Pyro solver, it’s intended to provide near-real-time viewport feedback on complex fire and smoke simulations, speeding up look development.

However, unlike the CPU-only Sparse Pyro, Axiom is GPU-accelerated via OpenCL, falling back to the CPU if a simulation exceeds GPU memory: each GB of GPU memory is enough for around 8.5 million voxels.

According to Puchala’s teaser video, simulations run 6-11x faster in Axiom than the Sparse Pyro solver.

(We haven’t seen any comparisons with Houdini’s Minimal OpenCL Solve mode, which wasn’t introduced until after the original release of Axiom, in Houdini 18.5.)

Controls for smoke and fire simulations – now including coloured smoke
Axiom can use either geometric primitives or VDB volumes as geometry sources, with Houdini 18.5 users getting support for NanoVDB, Nvidia’s simplified, high-speed, read-only representation of the VDB format.

It supports a range of “typical settings” for Houdini gaseous fluid simulations, including buoyancy, dissipation and turbulence; and fuel, density and temperature parameters for combustion sims.

To that, Build 4, released earlier this week, adds the option to use colour information from the source shape or VDB, and to advect colour data, making it possible to simulate coloured smoke and explosions.

Updated 15 March 2021: Matt Puchala has released Axiom Build 5.

Most of the changes are under the hood – according to Puchala, simulations are now 10% faster overall – although there is one new feature: that gravity can now affect fuel.

However, for new users, one key change will be a new and “hopefully easier to install” Houdini package, along with a video explaining in detail how to do so (embedded above).

Updated 17 May 2021: Axiom Build 6 is available.

The update adds “lots and lots of small features”, including new wind noise controls, a direction parameter for gravity, and new camera frustum, pump and pyramid source shape types.

Overall performance has been improved by a further “5-15%”, although it “depends greatly on hardware”.

Pricing and system requirements
Axiom is available for Houdini 17.5 and above, running on Windows, Linux and macOS. GPU acceleration is based on OpenCL 1.2, and supports current AMD and Nvidia GPUs. It’s a free download.

Read a full list of new features in Axiom in posts in the software’s Facebook user group

Download Axiom from Matt Puchala’s website (Registration required)
Also includes a link to the online documentation