testing: Add StandardShaderBall test scene and common models directory (#2149) Closes #1976 Adds a `render-shaderball` testsuite entry that renders the USD Working Group's [StandardShaderBall](https://github.com/usd-wg/assets/tree/main/full_assets/StandardShaderBall) asset in `testrender`, and introduces `testsuite/common/models/` as a home for geometry that more than one test can share. The shader ball is a widely used reference scene for evaluating material response (reflection, transmission, roughness, Fresnel, caustics, subsurface) so having it in the testsuite provides a somewhat realistic comparison against other renderers. The USD Working Group asset ships as USD with MaterialX shading networks. `testrender` only reads Wavefront OBJ, so the scene was imported into Blender and re-exported as OBJ + MTL. `testrender` already reads object names and material names out of the `.obj`/`.mtl`, which makes it straightforward to rebind the material assignments to OSL shader groups in the scene `.xml` description. All 12 material names map 1:1 onto shader groups in `scene.xml`. The USD asset was imported into Blender in the 'triangulated' `surface_geometry` variant to match the standard tessellation rate in `testrender`, which doesn't support subdivision surfaces. Assisted-by: Claude Code / Claude Opus 5 Used Claude Code to draft the two attribution READMEs and the notices embedded in the OBJ/MTL files. I verified the licensing facts against the upstream repository and edited the modification statement to correctly describe my changes to the model. ### `testrender` vs USD reference Reference images were rendered in Houdini's Karma renderer unless otherwise noted. Images shown here have been converted from EXR to PNG. **Basic test scene** | `testrender` | Reference | | --- | --- | | shaderball_default

| **Shader ball with correct UVs** | `testrender` | Reference | | --- | --- | | shaderball_uvgrid

| **Shader ball with subsurface geometry** | `testrender` | Reference | | --- | --- | | shaderball_glass

| #### Other `testrender` outputs **Shader ball with various materials** | Plastic | Metal | | --- | --- | | shaderball_plastic

| **Scene render passes** | Normal | UV | | --- | --- | | shaderball_normals

| ### Added **New test:** `testsuite/render-shaderball` — 160x120, `-aa 8`, using the same set of comparison settings as `render-uv` and `render-microfacet`, with `failthresh=0.01` and `allowfailures=3`. **Shared model directory:** `testsuite/common/models/`. `testsuite/common` is already copied into the build tree at configure time by `src/cmake/testing.cmake`, so tests reference models the same way they already reference `../common/textures/...`. `render-bunny`'s `bunny.obj` moves here too. **Shaders:** the ball itself uses a plain grey `glossy` (diffuse + GGX dielectric layer), with `diffuse_textured` on the enclosing box walls and `emitter` on the area-light geometry. `matte`, `emitter`, `glossy` and `metal` follow the existing per-test-directory convention and are unchanged copies of what other `render-*` tests already carry. `glass.osl`, `metal.osl` and `plastic.osl` are included but not instantiated in `scene.xml`. I used these to produce the preview renders above, and chose to include them in the `render-shaderball` test directory as a useful starting points for follow-up tests or experimentation. I'm happy to exclude them if reviewers would rather the directory only carry what the test uses. ### Licensing I'm not very experienced with asset licensing, so flagging a few things for review. I used Claude Opus 5 to help generate attribution information. The USD shaderball scene assets is licensed **CC BY 4.0**, which differs from OSL's BSD-3-Clause. See the USD Working Group's [`LICENCE`](https://github.com/usd-wg/assets/blob/main/full_assets/StandardShaderBall/LICENCE) for the scene. **To ensure attribution, I added:** * `testsuite/common/models/shaderball/README.md`: Carries the full attribution to authors (Chris Rydalch, André Mazzone, Thomas Anagnostou), the license and its URL, a link to the upstream `LICENCE`, and a description of the modifications made. * `testsuite/render-shaderball/maps/README.md`: Records that the textures are redistributed unmodified. * A notice embedded as comments at the top of `shaderball.obj` and `shaderball.mtl`, so attribution travels with the files if they're ever copied out of the repo. CC BY 4.0 imposes no share-alike obligation, so nothing here affects the licensing of OSL's own code. I've left the OSL repo's `THIRD-PARTY.md` alone for now, but I'm happy to add an entry there if maintainers would prefer `THIRD-PARTY.md` to list it. The only change to the modeled geometry is the addition of light-emitting planes in place of the upstream USD area lights, which have no OBJ representation and which `testrender` couldn't use anyway. This is all documented in the asset README. ### Repository Size The assets add ~7.2 MB: ~6.0 MB of textures, ~1.2 MB of geometry, and a 28 KB reference image. One texture map, `ground.ACEScg.exr`, alone is 4.2 MB. The textures are the USD WG files as-published. If this size increase is deemed to be too large for the repo, we could apply compression on the ground texture or remove the three `emitter_*` maps and `uvgrid.exr` (which currently only exist for the previews). ### Testing Both tests pass on the CI-OSL reference image [aswf/ci-osl:latest](https://hub.docker.com/r/aswf/ci-osl): ``` $ ctest --test-dir build -R 'render-(bunny|shaderball)' Start 584: render-bunny.opt 1/2 Test #584: render-bunny.opt ................. Passed 4.14 sec Start 604: render-shaderball.opt 2/2 Test #604: render-shaderball.opt ............ Passed 15.13 sec 100% tests passed, 0 tests failed out of 2 ``` Note that `render-bunny` needed re-verifying, since its model moved to `testsuite/common/models`. ### Known limitations and follow-ups for review * **CPU only.** There's no `OPTIX` marker file, so this doesn't currently run under OptiX. I don't have an OPTIX-capable GPU to validate against. Glad to add the marker file if someone with a GPU or CI can confirm it matches, or to leave it as a follow-up. Other platforms may need an alternate reference, as `render-microfacet` does for Mac ARM. * Camera position/angle in `testrender` is difficult to translate exactly from the USD scene. The angle used here is not 100% accurate to the USD camera, but produces a fairly similar image. * The ball uses a placeholder grey shader. Adding the glass and metal variants as their own tests seems like it would be the next step? --------- Signed-off-by: Jonathan Peters