# Render: what lives where
`render_frontend` reads the presented snapshot; `render_gpu` writes pixels and
owns `wgpu`. Rendering decides no gameplay and never writes `AuthorityWorld`.
| crate | role |
|---|---|
| `render_frontend` | scene preparation, culling, occupancy adapters, frame products and tessellation |
| `render_scene` | lighting, frustum, camera and occupancy storage; static light/BSP data publish on installation and clear on teardown |
| `render_anim`, `render_fx` | animation poses and effects |
| `render_frame` | immutable frame products, source revisions, packed segments and packing |
| `render_material`, `render_backend` | material tables and draw-list views |
| `render_gpu` | GPU preparation and recording |
| `render` | composition, extraction and diagnostics |
```text
zone → asset IR → prepare/scene/ → assemble/drawsurf/
     → sorted draw list → tessellation → material execution
     → SM3/WGSL → GPU contract → wgpu
```
One drawsurf machine accepts world, static-model and viewmodel emitters.
Lighting uses `lighting_iw4`, `smodel_lighting.rs` and `model_lighting_atlas.rs`;
shadows use `sun_shadow.rs`. `StaticSunAndFx` overlaps static sun preparation
with FX, joins before frame products consume results, then merges dynamic
casters. Sun model draws reuse colour geometry's index buffers.
Retained lanes in `retained_list/` key static reuse on world, material,
visibility and eye/LOD. FX also keys on distortion; glass re-sorts for each eye.
GPU skinning computes FPV and remote body packed vertices before native colour/shadows.
Shapes use stable IDs and retire with live jobs; invalid jobs refuse geometry.

GPU modules live in `render_gpu/src/drawsurf/colour_submit/`:

* `publication.rs` seals a frame against its installed world; both generations must match.
* `geometry.rs` and `residency.rs` track capacity, live length, allocation generation and uploaded revision. Shrinking retains buffers; changed packed segments upload alone.
* `binding.rs` and `constants.rs` cache textures and constants. Recording checks prepared work and table epochs against the extracted frame.
* `prepare_camera.rs` and `shadow_prepare.rs` prepare concurrently after shared shadow-view installation. Shadow frames remove dynamic tails and retain static patch targets. Multiple camera views refuse with `MultipleCameraViews`.
* `record.rs`, `encode.rs`, `shadow_encode.rs` and `indirect.rs` record draws. `IW4L_MULTI_DRAW` plus device support merges adjacent compatible commands while preserving order.

`extract.rs` replaces `InstalledRenderWorld` when geometry, ports or SMC maps
change and publishes `PublishedRenderFrame` each frame. `d3d9_decl`, `d3d9_sm3`
and `d3d9_state` describe D3D9 semantics; GPU adapters convert them to wgpu.
`session` installs matches; `assets` supplies bytes. Runtime switches use env
variables (`IW4L_SINGLE_CELL`, `IW4L_SUN_SHADOW_*`); observation uses
[`PERF.md`](PERF.md).

Film vision presets come from map/common fastfiles. Console `visionSetNaked`
and `visionReset` transition `FilmVisionView` between presets.

Packed skinning uses bounded output pages and per-batch palettes under actual device limits.
`IW4L_SKIN_RESIDENT_BYTES` defaults to 1073741824 (range 1048576–4294967296); invalid settings refuse support.
Readiness preflights the worst admitted player/corpse loadouts and FPV assembly, including replacement/retirement costs.
Cold shapes can leave GPU residency while their immutable CPU products remain valid; retired bytes stay counted until queue completion.
Capacity refusal is explicit and stops required presentation; there is no CPU skinning fallback.