# Imaging and meshing integration

Milestone 06 owns the native implementations in `libremetaverse-imaging`,
`libremetaverse-imaging-skia`, and `libremetaverse-prim-mesher`. The core
imaging and meshing crates contain no CLR bridge, subprocess adapter, foreign
RPC, or generated failure-only shim. The rendering crates consume the checked
mesh data but remain a separate milestone: `SimpleRenderer` now provides the
reference prim/sculpt conversion pipeline. `MeshFoundry` now adds bounded mesh
asset, rigging, tangent, secondary-UV, terrain, and convex-hull handling without
changing the milestone 06 ownership boundary. See the
[`SimpleRenderer` guide](../crates/libremetaverse-rendering-simple/README.md)
and [`MeshFoundry` guide](../crates/libremetaverse-rendering-mesh-foundry/README.md).

## Feature boundary

| Surface | Default build | Opt-in build | Native dependency |
| --- | --- | --- | --- |
| Managed images and TGA | enabled | n/a | none |
| JPEG 2000 | disabled | `libremetaverse-imaging/jpeg2000` | OpenJPEG 2.5.x |
| JPEG 2000 (pure Rust) | enabled | `libremetaverse-imaging/rust-j2k` | none (`j2k` 0.8.1) |
| BMP/GIF/ICO/JPEG/PNG/WBMP/WebP (pure Rust) | enabled | `libremetaverse-imaging-skia/rust-skia` | none (`skia-rs-codec` 0.3.0 plus `image-webp` 0.2.4) |
| BMP/GIF/ICO/JPEG/PNG/WBMP/WebP (native) | disabled | `libremetaverse-imaging-skia/skia` | Skia |
| Prim and sculpt meshing, OBJ ingestion | enabled | n/a | none |

OpenJPEG is a non-default workspace member so release tooling can package the
adapter explicitly, and imaging reaches it only through the optional
dependency. The default `rust-j2k` feature reaches only the audited pure-Rust
`j2k` graph; enabling both features keeps both explicit codec types available
for interoperability testing. Native Skia is likewise an optional,
target-specific dependency, while `rust-skia` is the raster crate default. The
consolidated required Gitea gate exercises the native feature, while a dedicated
`ubuntu-latest` job tests `rust-skia`, audits
its normal/build graph without installing native codec tools, and compiles the
same code for WASM. Minimal-feature checks still prove no codec is needed for
the owned Rust and translated compatibility tests.

## Bounds and rendering contract

Decoded images are limited to 4,096 by 4,096 pixels and encoded inputs to 64
MiB. Channel sizes, resize products, codec buffers, sculpt-map dimensions,
profile/path sizes, mesh vertex counts, face indices, viewer groups, and OBJ
indices use checked arithmetic before allocation or indexing. Malformed input
returns a typed error.

The rendering-facing integration tests verify that PrimMesh and SculptMesh
produce finite positions, normals, and UVs; aligned face and viewer-face data;
preserved prim-face grouping; in-range indices; and the 16-bit index range used
by the pinned MeshFoundry reference at every supported sculpt topology and LOD.

## Reproducible gates

Run the fixed ownership and feature audit with:

```console
python3 tools/check_milestone_06.py
```

The audit rejects owned Rust stubs, feature leakage, missing platform jobs,
missing performance targets, or drift in the 48 reviewed ManagedImage,
Coord/Quat, and PrimMesh compatibility cases. The required gate runs the native
crate and reviewed parity tests, Clippy with warnings denied, and rustdoc with
warnings denied. Benchmark compilation is retained in the non-routine release
gate.

The focused performance baselines are executable Rust programs rather than
wall-clock assertions, so slower shared runners do not weaken or destabilize
correctness tests:

```console
cargo bench -p libremetaverse-imaging --bench image_pipeline
cargo bench -p libremetaverse-prim-mesher --bench meshing
```

The image baseline clones, bilinearly resizes, and exports a 2,048-square RGBA
image. The meshing baseline builds and indexes a high-detail cut, hollow,
twisted circular extrusion. Both report elapsed time and allocation counts so
regressions can be compared using the same inputs.
