Plattipus Research and Production Lab has open sourced houdini-gsplat, a plugin that renders 3D Gaussian Splats natively inside Houdini 21 Solaris. A .ply capture flows directly into a LOP network via a PLY Import (Gaussian Splat) node, lands on the stage as a USD prim, and renders live in the Solaris viewport, without a disk write, no Python glue, or separate viewer. The release is MIT licensed.
The project is structured as four cooperating plugins built from one CMakeLists.txt. The first is a codeless USD schema that registers ParticleField3DGaussianSplat as a type hierarchy under UsdGeomGprim, with applied APIs for positions, orientations, scales, opacity, the EWA Gaussian ellipsoid kernel, and spherical harmonics. The second is a UsdVolParticleFieldImaging adapter that bridges the schema prim into Hydra's scene index. The third is HdParticleField, a CPU rasteriser that appears in the Solaris viewport renderer dropdown as "Particle Field (Gaussian Splat)". It does parallel depth sort across every (group × instance × splat) triple, projects each splat with the EWA Jacobian, fills pixels in row stripes across all cores, and evaluates degree 0–3 real spherical harmonics per-splat at the view direction. The fourth is Uruk.dylib, a DSO that registers three LOP operators: PLY Import, Gsplat Instancer, and Uruk itself.
For context on the broader Houdini-3DGS ecosystem, the existing open-source point of entry has been GSOPs from David Rhodes and Ruben Diaz, which radiancefields.com has covered across several releases. The original launch, the 2.0 early access, and the feature additions update. GSOPs is a SOP level toolkit aimed at authoring, editing, and processing splat data inside Houdini's geometry context. Plattipus is making Gaussian Splats behave like any other USD prim inside Solaris, so they can be referenced, overridden, layered, and instanced through the same composition arcs and scene graph machinery as everything else on a USD stage.
The instancer node is the part most likely to matter to studios working at scene scale. Gsplat Instancer writes a gsplat:instanceTransforms matrix4d[] primvar directly onto a prototype ParticleField3DGaussianSplat prim, and the Hydra delegate then renders N copies without duplicating the per-splat arrays. Memory scales as O(M + N) instead of O(N × M), where M is splats per cloud and N is instance count. Per-instance positions, scales, and orientations come from a points prim plumbed into the second input. The Uruk LOP builds a UsdGeomPointInstancer with per-point variant selection, which is useful for scattering assets that need per-instance LOD, material, or animation variant swaps.
Performance numbers in the README are from an Apple M1 Max at 1280 × 720 with 123,591 splats. The renderer is currently CPU only with no Metal or CUDA path, so scenes above roughly 500k splats will be slow at full resolution. macOS is the only platform exercised so far, though the CMakeLists.txt emits the correct RPATH form for Linux as well. Houdini 21.0.559+ is required because the build links exclusively against Houdini's bundled USD (currently 25.05); a standalone OpenUSD 26+ install is needed only for the optional ply2usd CLI, which exists for offline batch conversion.
For pipeline teams already invested in USD and Solaris, this is the first open source way to put Gaussian Splats on a stage as native prims rather than baking them into geometry or referencing an external viewer. It's available through GitHub.
