Houdini 22 Makes Gaussian Splats a First Class Citizen: Rigging, Relighting, and Reconstruction

SideFX Software announced Houdini 22 at a launch event in London, and gaussian splats are one of its two headline strategic initiatives alongside AI. What was a limited visualization and render experiment in Houdini 21 has been rebuilt as a full toolset woven into every stage of the CG pipeline, with new capabilities for rigging, animation, simulation, relighting, compositing, and generating splats directly from 3D renders.

Houdini 21 introduced native gaussian splatting support as what VP of Product Kristen Bergiel called "testing the waters", basic visualization, basic rendering, read only. The community had already long been pushing further than that, with GSOPs from CG Nomads providing SOP level manipulation tools that hit version 2.8 before this announcement.

The underlying principle is that gaussian splats are points with attributes, which means every node Houdini already has for manipulating geometry can be applied to them without modification. Bone Deform, Surface Deform, standard SOP nodes, all of it works on splat data. The keynote demo used this to rig and animate a Gaussian splat wasp using the standard Rig Builder, apply an insect rig template, switch between proxy/low-res/high-res LODs during interactive posing, and export an animated creature without any gaussian splatting specific rigging logic.

The animation demos pushed this further. A bar scene built entirely from a splat was used as a live animated set. An animator could select individual stool splats, remove them from the scene, pipe them into an Add Prop node to give them controls, then pose them like any other prop. Ragdoll's new impact threshold feature was then used to let a character kick those 3DGS stools over, with physics activation firing automatically on velocity rather than requiring manual keyframing.

The reconstructed wasp got secondary motion applied across its legs, antenna, and abdomen. Lag/overshoot, jiggle, and spring effects driven from a single root control, with transform multipliers per control to break twinning. Secondary motion blended directly into keyframe animation at the clip boundary.

The simulation demos are a practical answer to a real problem with splat deformation. Because lighting is baked view dependently into the splat data, heavy distortion makes the lighting look wrong. The keynote acknowledged this, noting it remains a "very tricky problem" the team is actively working on.

The most significant new capability is reconstructing 3DGS from Karma renders rather than photographs. The standard photogrammetric pipeline requires an SfM step to estimate camera positions. Houdini 22 does not handle that step yet, but when working from 3D scenes, the camera positions are already known exactly.

The workflow creates an array of cameras around a scene, renders them with Karma, and feeds those renders into the 3DGS training pipeline via PDG/TOPs. Because the source is CG rather than photography, the resulting G-splat can carry embedded normals, world space positions, and other arbitrary attributes alongside color.

The practical tradeoff was illustrated with a direct comparison. Animated OpenVDB fire at 180MB per frame versus animated splat fire at 45MB per frame, roughly a 4× reduction.

Viewport performance for 23 million splat scenes improved substantially from H21 to H22, driven largely by the move to Vulkan (OpenGL has been fully removed in this release). Side Effects framed Vulkan as foundational work toward a future cinematic near realtime renderer.

Karma's G-splat rendering path was completely rethought. The H21 approach on Karma XPU produced noisy results that required long resolve times; the H22 approach is described as a new implementation focused on quality, with visibly cleaner output demonstrated at the keynote.

Efforts toward relightable G-splats had been explored as a Houdini based proof of concept before this release. Houdini 22 ships prototype relighting tools from SideFX Labs that delight the splat, reconstruct surface information from normals, and apply new lighting via a Capernicus network. The wasp demo showed spherical harmonics applied to the wings under a new key light. These tools are labeled Labs/prototype rather than production-ready.

Copernicus (Houdini's compositor and texture-synthesis context) gains two new 3DGS specific nodes. The Camera COP allows cameras to exist inside Copernicus networks. The Rasterized splat node projects 3DGS into 2D, outputting both color and depth, enabling traditional compositing operations on splat imagery. A live demo applied chromatic aberration to a Karma render interactively from inside Copernicus, with results updating as the splat was re-rendered.

Depth output from the rasterized node enables depth based compositing and lens effects, and integrates with Copernicus's new caustics from height and refract from height tools.

Houdini 22 is available now.