Smart Python
Houdini 11 sees the switch to Python 2.6 from 2.5. Users now also have the option to choose which Python distribution they prefer, which will be a nice addition for Houdini's power Python/HOM users (this includes Hython, the command line implementation). Houdini now will also attempt to match the currently installed system distribution of Python, so if a user has 2.5 installed, Houdini will use 2.5, if 2.6 is installed it will switch to 2.6. If the user has no version installed, Houdini will use the 2.6 distribution, which it ships with. There are no specific changes to how Python is implemented, however, meaning on many occasions node expressions in Houdini's native H-script and/or the expression language still execute faster.

Lights, Camera, Render!
With regard to lighting and rendering, Houdini 11 has concentrated on the improvement of existing tools, but has also introduced one or two new ones. First, there are substantial improvements to the handy environment light. This now gives overall better performance than the already impressive render times seen in Houdini 10. The environment light also has new features including a "portal light," which simulates environment lightning from a limited source, like a through a window, and sky lighting with physically correct time-dependant positioning of the sun. Another welcome improvement is support for multiple environment lights in the same scene, which correctly interact with regard to luminance accumulation and shadow interaction.

One of the new implementations mentioned to lighting comes in the form of the geometry light. This will cast light from geometry in accordance with the objects shader parameters (for example, the color of the emitted light is picked up from the shader color). What is most fun about this tool is that it supports animated geometry, including geometry animated dynamically through a simulation, which can make for some very interesting lighting effects. One drawback is that the geometry light can become computationally expensive, but used astutely this is a very interesting and potentially useful tool.

Other improvements to lighting include performance enhancements for area lights, a handy ready set-up three point light rig to simulate the traditional key, fill and bounce scenario and the new indirect light, which gathers the functionality of many previous tools centering around indirect illumination, such as GI, caustic effects and photon mapping all in one place.

After IPR (Interactive Preview Rendering) mysteriously disappeared from Houdini 9, it had a welcome re-introduction in 10 and has now been upgraded. IPR can now be network distributed and is also compatible with the useful region render tool.

Other miscellaneous improvements include new CHOPs centered on crowd simulation, support for Disney's Ptex format, a range of new fur styling tools and an impressive array of new volume manipulation sop level tools. One last note, there is a new "lazy-line" option for node wiring, which I found so amusing I thought it worth a mention!

In conclusion, Houdini 11 sees some very noteworthy improvements. FLIP solver fluids will make a huge difference in the use of Houdini based fluids in production and is a major enhancement to Houdini's fluid arsenal. Efficiency and ease of use enhancements to lighting tools and the RBD toolset will also enable faster turnaround of common VFX tasks. One downside to the release is the lack of any real brand new "hero" tools, but the introductions to augment existing toolsets are excellent.

Alexander Carson-Brown is a long time Houdini user and a graduate from Bournemouth University’s MA Digital Effects programme in the UK. He is now an FX-TD in the motion picture industry and has produced effects work for numerous commercial spots and many films, including Harry Potter and the Half Blood Prince, Alvin and the Chipmunks 2, Wanted and The Golden Compass.