iw4L/docs/RENDER.md

Render: what lives where

Nine crates. render_frontend reads the presented snapshot, render_gpu writes the pixels and solely owns wgpu. The island decides no game logic, never writes AuthorityWorld, decodes no assets.

crate	owns
render_frontend	prepare/ scene, view, cull (scene/{world,spawn,cull,camera}.rs, scene/gfx_scene.rs anim-submission bridge, worker_cmds.rs); adapters/ occupancy out of anim and FX; assemble/ frame products (drawsurf/{retained_list,frame_products,material_runtime}.rs, drawsurf/tess/)
render_scene	occupancy storage: lighting request/result, frustum planes, camera pose. render_anim / render_fx produce the poses and FX
render_frame	the immutable frame-product snapshot at the frontend ↔ GPU border (SourceRevisions, PackedSegments, pure packing)
render_material, render_backend	the material tables; the list views
render	composition, extract.rs, diag/

The frame path

zone → asset_iw4 IR → prepare/scene/world.rs (our own types) → spawn.rs (GPU)
     camera.rs (look/WASD), frustum.rs + cull.rs + dpvs_iw4
     → assemble/drawsurf/list.rs   ONE sorted GfxDrawSurf[]
       → setup.rs  techType → technique      → state.rs  GfxPassState / blend
       → tess/{world,smodel,xmodel,fx,mark,glass,particle_cloud}.rs
       → material_runtime.rs   N-pass execution or a typed refusal
       → sm3*.rs   SM3 tokens (`d3d9_sm3`) → WGSL → gpu_contract.rs → wgpu

One drawsurf machine; only the tess emitters fork per surface type. World, static models and the viewmodel are three emitters into one list, not three renderers. Lighting is lighting_iw4 (light grid) with prepare/scene/smodel_lighting.rs and model_lighting_atlas.rs, shadows assemble/drawsurf/sun_shadow.rs.

GPU-side ownership: render_gpu/src/drawsurf/colour_submit/, three owners

• geometry.rs + residency.rs — residency. Capacity, live length, allocation generation and uploaded revision are four quantities: a shrunk frame keeps its buffer and a changed PackedSegments segment uploads alone;
• prepare_camera.rs — shared installation resets generations and publishes shadow views; sun, spot and camera then prepare in order, on pass-local executors. A second Camera3d is the typed refusal MultipleCameraViews;
• record.rs + indirect.rs — recording. Direct path draw_indexed; with IW4L_MULTI_DRAW and the indirect downlevel flags, adjacent compatible runs merge into one multi_draw_indexed_indirect, order preserved.

extract.rs publishes InstalledRenderWorld when static geometry, ports or SMC maps change, and PublishedRenderFrame every frame. d3d9_decl / d3d9_sm3 / d3d9_state carry D3D9 semantics with no word about IW4; the only D3D9 → wgpu crossing is the adapter inside render, while session stands the match up and assets owns the bytes. No live r_* dvars: env vars (IW4L_SINGLE_CELL, IW4L_SUN_SHADOW_*, …) and Perfetto (IW4L_PERF=1, PERF.md).