gromandClaude Opus 5
b6f3bb001c
The reference ships `anisotropic` at 1, which is *off*, so ground texture at a
grazing angle smears to mush a few yards out — which is most of the screen in
an outdoor scene. The row was registered and wired (`benilla_assets::
TexFilterSetting`, the reference's own `[1, 16]` clamp at `0x689110`) but sat
outside the preset ladder, so no rung ever spent it and even Ultra left it off.
Measured on an Elwynn vista (`WOW_CAPTURE=vista`, the offline harness
`docs/GRAPHICS.md` now documents), one knob changed, 1600x900:
* **34.1% of the frame moves** (490,600 of 1,440,000 pixels by more than 2),
mean |d| 4.21, max 212. By band it peaks at **66.5%** across y 420-479 and
runs 48-66% from y 300 to y 780 — exactly where the ground recedes to the
horizon, which is what anisotropy is for. For scale, the interior
prop-probe table's whole stake is 7.6% of pixels by at most 14.
* **+1.0 ms of GPU and nothing on the main thread** (gpu 0.8 -> 1.8 ms, main
unchanged at 4.2-8.4 ms). The filter policy confirms it lands: "mode 4
(trilinear, aniso off)" -> "mode 5 (trilinear + aniso) anisotropic=16".
That ms is one this client is not spending. It is main-thread bound with the
GPU about two thirds idle — flat ~3 ms in play at every framerate, 0.8 ms in
this capture — so a sampler state is the cheapest picture on the table.
Ladder: Classic and Low keep the reference's 1, Medium takes 4, High and Ultra
16. Classic is the reference client, so it is judged against the registered
default the way `farclip` already is, not against zero — `anisotropic` is not a
0/1 lane, its "off" *is* 1. The High column differs from the reference, so it
is declared in `SEEDED_DEVIATIONS` with its reason, and
`graphics_rows_pass_their_observers_unclamped` now drives all five rungs
through the real setter and reads the level back off the sampler policy.
The sampler is baked into each texture at load, so a rung change lands on the
next launch, as the reference's own options window says ("enabled upon
restart"). A player already on a Custom preset is not seeded and keeps their
saved value; `/console anisotropic 16` and a restart is the whole fix there.
`docs/GRAPHICS.md` is new: where the frame's budget actually is, the offline
capture-and-diff harness every claim here uses, what is already shipped and
unspent, and the ordered list of what the picture is missing — costed on this
engine, with upscaling placed where the measurement puts it rather than where
it is usually asked for.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SgstFWtn1RxEJ5kVrpgYwn
150 lines
8.1 KiB
Markdown
150 lines
8.1 KiB
Markdown
# Graphics: where the budget is, and where the picture is
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This fork's renderer is its own (`LIGHTING.md`, `WATER.md` describe the lanes). This file is the
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*plan*: what the frame actually costs, what is already shipped and unspent, what is missing, and
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what each missing thing would cost on **this** engine rather than on someone else's.
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## The budget, measured
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**This client is main-thread CPU bound and the GPU is about two thirds idle.** Measured with
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`WOW_FLASH_TRACE=1 WOW_GPU_MS=1`, in play and offline:
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| | fps | wall | main | gpu |
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|---|---|---|---|---|
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| live, Dun Morogh, out of combat | 112 | 8.9 | 7.6 | **3.0** |
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| live, in combat | 65–91 | 11.1–15.4 | 10.3–14.5 | **2.6–3.9** |
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| offline Elwynn vista, vsync-capped | 60 | 16.6 | 4.2–8.4 | **0.8** |
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`gpu` is flat at every framerate; `main` moves 1:1 with the drop. So the rule for anything in this
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file:
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> **A change that spends GPU is nearly free. A change that adds main-thread work is not.**
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That single fact decides most of the ordering below, and it is why upscaling is near the bottom
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rather than the top.
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## The harness
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Every claim here is checked the same way, offline, with no server and no account — about 60 s a run:
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```bash
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env WOW_DATA=/path/to/Data WOW_MAP=0 WOW_CAPTURE=vista \
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WOW_VISTA_AT=-9460,70,58 WOW_VISTA_FACE=180 WOW_VISTA_PITCH=-8 WOW_VISTA_MIN=720 \
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WOW_GPU_MS=1 WOW_FLASH_TRACE=1 WOW_CAPTURE_OUT=/tmp/shot.png \
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cargo run -q --release -p benilla
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```
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Render it twice, change one knob, and diff the PNGs (`PIL.ImageChops.difference`): mean and max
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absolute difference, and the count of pixels that moved by more than 2. `WOW_CVAR=a=1;b=2` sets any
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registered row for the session; `WOW_ANISO`, `WOW_FARCLIP`, `WOW_RENDER_SCALE`, `WOW_MSAA` are
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direct levers. Validated eye positions live in `benilla-app/src/capture/scenarios.rs`.
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**Always run a starved control.** A knob that forces the bad path, or an identical pair of renders,
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proves the harness is actually reaching the thing being measured. Five such pairs once matched byte
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for byte before anyone checked whether the view read the table at all.
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## Already shipped and worth spending
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These need no code. They are the cheapest picture available today.
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| Knob | Shipped | Worth | Measured cost | Measured change |
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|---|---|---|---|---|
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| `anisotropic` | 1 (off) at Classic/Low, **16 from High** | 16 | **+1.0 ms GPU, 0 main** | **34.1% of the frame**, peaking at 66.5% across the band where the ground recedes |
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| `renderScale` | 1.0 (Render Scale slider in Options) | 1.25–1.5 | +1.5 ms GPU, 0 main | 19.4% of the frame |
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| `farclip` | 777 at High, 1497 at Ultra | taste | streaming and draws, i.e. **main thread** — measure before raising | — |
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The anisotropic row is the one to take first: the reference ships it *off*, so ground texture at a
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grazing angle smears to mush a few yards out, which is most of an outdoor screen. It is a sampler
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state, so it is free on the CPU and costs a milligram of the GPU time we are not using. The sampler
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is baked into each texture at load, so a change lands on the **next launch** — the reference's own
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options window says the same ("enabled upon restart").
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A player already on a **Custom** Graphics Preset is not seeded by the ladder and keeps their saved
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value; `/console anisotropic 16` and a restart is the whole fix for them.
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## What the picture is missing
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Ordered by (visual gain) ÷ (main-thread cost), not by how interesting they are.
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### 1. Terrain horizon occlusion — *buys* main thread
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The reference culls terrain against its own horizon (`0x686000`, `0x686180`, `0x681b50`), outdoors
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and per portal window inside a WMO, and parks hidden rigs and drops shadow casters below it. We have
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the portal/doorway half (`exterior_cull.rs`) and not this one. It is the rare item that makes the
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frame **cheaper on the thread that is actually full**, and cheaper frames are what let the view
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distance and the lanes below be afforded at all. Terrain chunk LOD (`0x6c51b0`, levels 2 and 3
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stitched across cell and tile edges) is the same kind of win.
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### 2. Auto-exposure
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A screen-metered exposure, so interiors, night and a torchlit room read at their own level instead
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of at the sun's. One GPU pass over a downsampled frame plus a smoothed histogram; our HDR path and
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`ffx_glow`'s combine already carry an exposure slot. Small, GPU-side, and it changes every dark
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scene in the game.
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### 3. Planar water reflection
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Our water has refraction, foam and a scene-depth copy (`liquid/`, `water_fx/`) but no mirror. The
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reference-era trick is a second scene render with an oblique near clip, armed only for visible water
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and thinned of small objects, under a screen-space trace. It is the single most recognisable item on
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the "original art, modern presentation" axis, and it is pure GPU — which is what we have.
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### 4. Froxel volumetrics
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We have near-field volumetric fog and light shafts as screen passes. The modern form solves the DBC
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fog into a participating medium in a 3D froxel volume with reprojected history, so fog lights
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correctly, moves with the camera without swimming, and costs a fixed compute dispatch instead of
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scaling with overdraw.
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### 5. Screen-space indirect light (SSILVB)
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An upgrade from classic SSAO to a visibility-bitmask trace that carries indirect *colour*, not only
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occlusion. GPU-side, and it is most of what makes a modern frame look lit rather than painted.
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### 6. Runtime probe GI
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A toroidal voxel clipmap of the static world plus cascaded probe grids traced in compute, order-1 SH
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with hysteresis. The biggest lighting change available and the most work; it belongs after the five
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above, not before.
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### 7. Upscaling (FSR) — **not now**
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Worth stating plainly, because it is the obvious thing to ask for. FSR renders *fewer* pixels and
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reconstructs the rest. We are not short of pixels — we are short of main thread, and the GPU is two
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thirds idle. Upscaling would hand back time we are not spending and charge main-thread work for it:
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a motion-vector prepass over terrain, static geometry and every skinned rig, plus the upscaler's own
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dispatch.
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The plumbing, for when it *is* the right lever:
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* Bevy 0.18 already carries `MainPassResolutionOverride` (honoured by every main 3D pass) and
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`TemporalJitter`, and ships a complete DLSS integration (`bevy_anti_alias::dlss`) built as a
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**`ViewNode`** — the same render-graph shape this tree uses, so it is a working template rather
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than a port.
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* `renderScale` already decouples world resolution from the window (`world_backdrop.rs`), with its
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own Options slider. The resolution half of the problem is solved.
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* The real work is motion vectors for **our** skinning: `wow_model.wgsl` runs its own
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`wow_skin_model` off our rig palette at vertex locations 10/11, not Bevy's `SkinnedMesh` path, so
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Bevy's prepass would draw every animated model unposed. A prepass variant needs the palette
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double-buffered to last frame's pose.
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* **RCAS sharpening** is the separable piece: a single cheap post pass that improves perceived
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detail at any render scale, including above 1.0. It needs none of the above.
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* Frame generation is *not* reachable here: it needs a winit `AfterUpdate` hook that Bevy does not
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expose, which is why the fork that has it vendors `bevy_winit`.
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### 8. Field of view
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The reference's lens is ~44.1° vertical at 16:9 and ours is 45°, so ~73° horizontal. A 90° Hor+ lens
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is a large perceptual change and nearly free to draw. It is deliberately **not** on this list as a
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default change: it alters how the game feels to play, and the existing `FoV` row is SuperWoW's
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camera *ratio* (`crate::player::scoped_view::CameraFov`), which is a different quantity. If it is
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wanted it should be its own registered row with the reference's value as the default.
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## What is not in scope
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`benilla-bourbon` implements most of §2–§7 already, on **Bevy 0.19.1** with a vendored wgpu 29 and a
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render graph expressed as systems. This tree is Bevy 0.18.1 with 14 files implementing render-graph
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`Node`s. Those are incompatible architectures, and that fork is published as one squash commit with
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no history to pick from — `docs/BOURBON_SYNC.md` has the measurement. So everything above is costed
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as *work on this engine*, informed by what that fork proved is possible, not as a port.
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