@archiyou/collada-wasm

COLLADA (.dae) writer for Archiyou: a small Rust crate compiled to WebAssembly, built on a vendored + patched copy of collada_io 0.1.0 (MIT OR Apache-2.0).

Used by packages/core/src/modeler/DAEExporter.ts, which walks the meshup scene graph and drives this writer. See Modeler.toDAE().

Install

npm install @archiyou/collada-wasm

Why the crate is vendored

Upstream is unmaintained (published 2020), undocumented, and its writer was missing most of what we need. Rather than depend on it, src/collada_io/ holds a patched copy — the same approach packages/gdrr2bp-wasm takes with gdrr-2bp. Every change is marked // vendored: and listed in the patch log at the top of src/collada_io/mod.rs:

| Patch | What | |---|---| | P1 | <unit> emitted unit="…"; the spec attribute is name="…" — importers read model scale from it | | P2 | <created>/<modified> were RFC2822, not xs:dateTime. Now caller-supplied strings, which also drops the chrono dependency | | P3 | Added library_effects + library_materials (upstream had none; its fx/ directory is unreferenced and does not compile) | | P4 | Added <lines> for curves | | P4b | Added <polylist> + <vcount> so n-gon faces survive | | P4c | <mesh> can now carry triangles / polylist / lines instead of exactly one Triangles | | P5 | bind_material was dropped on the floor (// TODO), so materials could never be bound | | P6 | Removed unreachable/unfinished types | | P7 | Node had no children — only a flat node list was possible | | P8 | #[derive(Clone)] on the writer types |

API

Two phases, mirroring COLLADA's own structure: library_geometries is a flat pool, while library_visual_scenes is a tree.

import { createColladaWriter } from '@archiyou/collada-wasm';

const writer = await createColladaWriter({ unitName: 'millimeter', meter: 0.001 });
try {
    writer.addMaterial('mat_0', 'Oak', 0.8, 0.6, 0.3, 1);
    writer.addPolylistGeometry('geom_0', 'Box', positions, normals, vcount);

    writer.beginNode('walls', 'walls');
        writer.beginNode('geom_0_node', 'Box');
        writer.attachGeometry('geom_0', 'mat_0');
        writer.endNode();
    writer.endNode();

    const dae = writer.toStringDae();
} finally {
    writer.free();
}

Welding

Vertex welding happens here, not in meshup. meshup already has an equivalent welder in Rust (rust/src/mesh/mod.rs get_vertices_and_indices), but it is not exposed to WASM, and exposing it would mean rebuilding meshup's wasm binary — which in this repo is ahead of its csgrs submodule pin, so rebuilding regresses rings, silhouette and reconstruct_ngons. Welding a buffer we already hold is far cheaper than that risk.

Positions and normals weld independently into separate sources with separate <input> offsets — the standard COLLADA layout, and where most of the size win is: a cube goes from 36 loose vertices to 6 quad faces over 8 positions and 6 normals.

The welder is grid-quantized (HashMap<[i64;3], u32> keyed on (v / tol).round()), matching what meshup's own welder does. Two points closer than the tolerance can occasionally land in different cells and stay unwelded; it never merges points it shouldn't, which is the direction that matters.

Build

pnpm --filter @archiyou/collada-wasm build:wasm   # wasm-pack + inline base64
cargo test                                        # native smoke tests

ts/wasm/ and ts/collada-wasm-binary.ts are committed, and the base64 is regenerated by buildscripts/build-wasm.ts — never by hand. A fresh clone therefore needs no Rust toolchain, and there is deliberately no build script, so turbo build never requires one either.

wasm-pack's built-in wasm-opt step was observed respawning in a loop here, so the build passes --no-opt and runs wasm-opt itself, where a failure is non-fatal.

Known limitations

• Nodes are all identity transforms (meshup bakes transforms into geometry), so the hierarchy is organisational, not transformational — moving a parent node in a DCC app will not behave the way it does in Archiyou.
• No UVs or textures: meshup meshes carry no UVs at all (the glTF exporter synthesizes them), so materials are flat lambert diffuse colour only.
• Vertex shapes are skipped — there is no point primitive here.
• N-gon faces with holes are triangulated; <polylist> cannot express a hole. Hole-free faces keep their original topology.
• Face normals come from the polygon plane, not the per-vertex normals, which lose their sign in meshup (a box reports only 3 distinct vertex normals instead of 6).