houdini-gsplat

houdini-gsplat is an open source plugin from Plattipus Research and Production Lab, a Sydney production company and research lab, that renders 3D Gaussian Splats natively inside Houdini 21 Solaris. Plattipus open sourced it in May 2026 under the MIT licence, and the repository at github.com/plattipus/houdini-gsplat has no tagged releases, so it is built from source.

Four plugins build from one CMakeLists.txt. A codeless USD schema registers the ParticleField3DGaussianSplat prim type with applied APIs for positions, orientations, scales, opacity, the Gaussian ellipsoid kernel and spherical harmonics, matching the particle field schema family that OpenUSD 26.03 added for Gaussian Splats. A UsdImaging adapter bridges that prim into Hydra, and HdParticleField, a multithreaded CPU rasteriser, appears in the Solaris viewport renderer menu as Particle Field (Gaussian Splat) and evaluates spherical harmonics up to degree 3 per splat.

The fourth plugin registers three LOP nodes. PLY Import reads a binary or ASCII 3DGS .ply straight onto the stage without a disk write or Python, either as a splat prim or as UsdGeomPoints. Gsplat Instancer writes a matrix4d[] instance transform primvar onto a prototype prim so N copies render without duplicating per splat arrays, scaling memory as O(M + N) instead of O(N × M). Uruk builds a UsdGeomPointInstancer with per point variant selection. An optional ply2usd command line tool converts .ply files to .usdc or .usda offline and needs a separate OpenUSD 26 or later install.

Houdini 21.0.559 or later is required, because the build links only against the USD 25.05 that Houdini bundles. The README lists the limits plainly. Rendering is CPU only, Karma and Storm ignore splat prims, so a Points output mode gives Storm an approximation, time varying attributes are not interpolated, and only macOS on Apple Silicon has been tested, although the build emits the correct paths for Linux. Published performance notes come from an Apple M1 Max at 1280 × 720 with 123,591 splats.

Inside Houdini, the longer standing open source entry point is GSOPs, a SOP level toolkit for editing and processing splat data. houdini-gsplat instead treats a splat capture as a USD prim that can be referenced, layered, overridden and instanced through ordinary composition.