[yujiaxu-ops]

Step 1 of the plan for the live passes' layout. Adding a buffer and a pass in #67 took seven edits that had to agree with one another:

1. the declaration in live.wgsl;
2. the bind group layout's entries;
3. the pass list;
4. the buffers' sizes and order;
5. the bind group's entries;
6. the dispatch grid, which existed in two copies;
7. the merged layout's table.

Tier R1: no picture changes.

The change

• renderer/build.rs reads shaders/live.wgsl with naga when the crate is built. naga is the compiler wgpu uses, at the same version (30). It is a build dependency, so the browser's wasm build carries none of it. From the shader it gets each binding's name, number, kind and element stride, and the bindings each entry point uses.
• renderer/src/live/layout.rs holds only what the shader cannot say:
  • RESOURCES: what each binding is bound to (a buffer of the passes' own, the frame's parameters, the trace's samples, the kernel's outputs, the LUT), and how many elements an own buffer holds (per output pixel ×k, quarter grid, bloom pyramid, or the length the shader declares);
  • PASSES: the passes' order and the grid each runs over.
• layout::check holds the table to the shader: every binding has one resource of a fitting kind, and every entry point is a pass, each exactly once. It runs as a unit test and at every view's start, and names what disagrees.
• Natively each pass has its own bind group layout and bind group, covering only the bindings its entry point uses. Before, every pass shared one group holding every binding.
• The browser keeps the merged layout for all passes for now. 36 of the 39 passes bind at most the browser's eight storage buffers. The other three are post (13, most of them its debug view modes), compose (11) and dtemporal (10). Step 2 rearranges those three; then the browser can use the same layout and merged.rs's live half goes.
• Targets allocates from the table (buf(name)), and pass_grid became layout::Grid::size.

From now on, a buffer or a pass more means its declaration in live.wgsl and a line in live/layout.rs.

Merge gate (R1)

check	result
cargo test --release	125 passed (the new one: the table and the shader agree)
render-identity vs the build before, native	190 outputs: 171 byte-identical, 19 within run-to-run spread, 0 changed
render-identity, THREERT_MERGED=1	172 byte-identical, 18 within spread, 0 changed
cost	the passes after the trace 6.03–6.09 ms on both builds (Bistro, 1440p at 0.375, alternated, six prints each)
wasm32 library, web crate	build (the web crate's lock gains naga as a build dependency)
npm	not touched

ROADMAP § 1a records the step.

🤖 Generated with Claude Code

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Note

Medium Risk
Refactors core live-rendering bind layouts and buffer wiring across all passes; mitigated by layout/shader validation and reported render-identity parity, but mistakes here would surface as subtle GPU bugs.

Overview
Centralizes live GPU pass layout so live.wgsl is the source of truth for bindings and entry-point usage, with a small Rust table only for what WGSL cannot express (buffer sizes, pass order, dispatch grids).

Adds renderer/build.rs (naga build dependency) to generate BINDINGS and ENTRY_POINTS from the shader at compile time. renderer/src/live/layout.rs holds RESOURCES, PASSES, and layout::check to keep the table and shader in sync (unit test + called at view startup). pass_grid and scattered manual layout tables are replaced by layout::Grid and generated metadata.

Natively, each of the 39 compute passes now gets its own bind group layout and bind group (only the bindings that entry point uses); dispatch uses the per-pass grid from PASSES. Web builds still use the merged single layout until post, compose, and dtemporal are refactored.

Targets stops hard-coding one field per buffer: allocation and bind groups are driven from the layout table (buf(name), bind_groups). LoadedScene carries bgs: Vec<_> instead of one shared bg; frame.rs binds self.sc.bgs[k] per pass. Docs (ROADMAP, RUNTIME) note the change; wasm lockfile picks up naga as a build-only dep.

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