### Goal Close #132's remaining acceptance criterion — *"free-fly navigation through the scene in Studio at interactive framerate"* — and give the engine a scalability story it currently does not have. Reported today on `../turian-samples/bistro`: **~20 fps in the Scene viewport, 9–20 fps in Play**, only marginally better from a compiled build. A real game has to fit physics, gameplay, audio and scripting into the same frame, so the renderer needs a lot more headroom than that. Full analysis and the ordered plan: `docs/decisions/bistro-performance-132.md`. ### The scene, measured Parsed from the cooked boot scene and the TMSH v2 mesh headers: | | Bistro Exterior | Bistro Interior | Total | |---|---|---|---| | triangles | 2,832,120 | 1,320,323 | **4,152,443** | | submeshes | 1,591 | 2,289 | **3,880** | | material slots | 132 | 74 | **206** | 18 nodes total — the whole scene is two `mesh_renderer`s plus 5 lights, 5 cameras, an environment, a post-process volume, 2 reflection probes and 4 scripts. There is no LOD system (#39), so all 4.15M triangles are submitted at every distance, from every pass. ### What the frame does (read from code) 1. **A full asset re-scan every frame.** `assets.uploadNewAssets` resolves all 206 material GUIDs and 5 map slots each through three O(n) linear caches — ~3×10⁵ string comparisons per frame to learn nothing changed. 2. **The prepass issues 3,880 draw calls where the main pass issues 206.** `prepass.run` loops submeshes with a `resolveMaterial`, two uniform pushes and a sampler bind each; the main pass draws the same geometry with 206 indirect multi-draws. The prepass runs *before* the cull dispatch, so it can't reuse `gm.indirect_buf`. 3. **Four shadow cascades re-submit the whole scene every frame** — 824 indirect multi-draws walking 15,520 indirect commands, for a static scene under a static sun. 4. **4× MSAA, forced.** `pipeline.pickSampleCount` has no override anywhere. 5. **SSAO and SSR at full resolution** — 24 AO taps and a 32-step march. 6. **576 bytes of mostly frame-constant uniform pushed per draw.** 7. **More than one whole-scene render per editor frame** in some layouts, plus the 10 Hz camera-preview inset. ### Status **115.7 ms → 12.8 ms (8.6 → 78 fps), 9.0x**, from #162 and #161 alone — no fidelity change, both verified pixel-identical. Current numbers and per-pass split: `docs/decisions/bistro-perf-baseline.md`. The shape has changed enough that the ordering below was re-derived after re-baselining: `render.scene` is now 5.62 ms of a 10.04 ms CPU frame, editor UI is the other ~4.4 ms, and the transparent pass (#168) is the largest single render cost. ### Original measurement (2026-08-23) `docs/decisions/bistro-perf-baseline.md`, from the #159 harness. Bistro, elevated terrace, 1280x720, Debug, RX 6700 XT: **p50 = 115.7 ms — 8.6 fps. 4,006 draw calls/frame. The frame is CPU-bound: 112.9 ms of CPU against a 118.1 ms period (96 %).** | pass | CPU | draws | indirect | tris | |---|---|---|---|---| | **render.prepass** | **71.86 ms** | **2,435** | 0 | 2,479,823 | | render.main | 16.39 ms | 194 | 3,271 | 3,734,581 | | render.upload | 12.39 ms | 0 | 0 | 0 | | render.shadow | 7.44 ms | 776 | 13,084 | 14,938,324 | | render.transparent | 2.60 ms | 601 | 0 | 416,834 | | ssao / ssr / cull / postprocess | < 0.1 ms each | 0 | 0 | 0 | The list above was written from code reading; the measurement confirms items 1 and 2 and reorders everything else. Two findings changed the plan: - **Per-pass GPU fences (#159 item 0d) are off the critical path** — no point timing a GPU that idles for 96 % of the frame. - **#162 and #161 are 73 % of the frame between them**, with no fidelity change, so they move ahead of the quality toggles. ### Phases **Phase 0 — instrumentation. Done.** - [x] #159 Headless benchmark mode, per-pass counters, edit-mode profiling. Output: `docs/decisions/bistro-perf-baseline.md`. (Item 0d, per-pass GPU fences, deferred — see below.) **Phase 1 — the free wins** (no fidelity change). **Done — 115.7 ms → 12.8 ms, 9.0x.** - [x] #162 Prepass issued 2,435 draw calls where the main pass issued 194 — 71.9 ms → 0.38 ms - [x] #161 Per-frame asset re-scan and linear GUID lookups — 12.4 ms → 0.26 ms, and `render.main` 16.4 → 3.9 ms - [ ] #163 Frame-constant data re-pushed in every 576-byte per-draw uniform — now small - [ ] #164 Studio renders the whole scene more than once per editor frame — now small **Phase 1b — what the re-baseline exposed.** - [ ] #168 Transparent pass is 601 per-submesh draws, now the largest render cost at 2.47 ms (44 % of `render.scene`) **Phase 2 — a quality dial.** - [ ] #160 Per-feature rendering toggles + `graphics.quality` presets that finally mean something. - [ ] #169 Player-facing settings screen in the shipped game (builds on #160) **Phase 3 — shadow cost.** - [ ] #165 Cascades re-submit the whole scene 4x every frame **Phase 4 — cut the geometry at source.** - [ ] #39 LOD system — the only thing that addresses 4.15M triangles at source **Follow-up, unscheduled.** - [ ] #167 GPU occlusion culling (HZB over the prepass depth) Diffuse GI (#166) is scheduled *after* all of the above — it adds frame cost to a scene that can't afford it yet. ### Related - #132 Bistro sample — the driving use case - #147 Frame performance analysis — built the fence-timing tooling, never got live numbers - #143 Frustum culling, ADR-0013 GPU-driven culling — the previous rounds - #39 LOD system — phase 4