Occlusion culling (#108)

.claude/skills/rokubot-examples/SKILL.md

@@ -202,9 +202,9 @@ channel back to Home).
 | `canvas` | Demonstrates panning/scaling the whole game **canvas** (offset/scale), not an on-screen entity. On-screen text/rectangle are drawn on the separate UI layer, so the pan/scale effect isn't visible in a screenshot even though it's working — don't mistake that for a bug. | arrows = pan canvas, `info`/`instantreplay` = scale up/down, `play` = re-center |
 | `quickstart` | Minimal scaffold-template app: one white square, moves freely. Good smoke-test for "is the toolchain working." | arrows (any direction, free movement via `input.x`/`input.y`) |
 | `platformer` | "Jungle Adventure" side-scroller: 7 levels, the last a one-screen boss fight (a pop-up Venus fly trap that fires aimed fireballs and dies after 3 head stomps). `--param level=N` (1-based) skips the title screen straight to level N, e.g. `level=7` for the boss. | `left`/`right` run, `select` (OK) jumps, `back` pauses, `info` (options) toggles debug overlay + collider outlines |
-| `rendererTest` | Categorized, menu-driven suite of `BGE.Renderer` demos - deliberately **not** built on `BGE.Game`/`GameScene` (see `CLAUDE.md`'s "Manually exercising the Renderer" note for the architecture and how to add a new demo). Grouped by category on an on-screen menu. Every demo shows an automatic timing line (fps / frame ms / update ms / draw ms / draw calls), so this is the place to *measure* a draw-cost question rather than reason about it - the `quad-fill-benchmark` demo times two fill approaches head to head in one run. | `up`/`down` = select in menu, `select` (OK) = run selected demo / demo-specific action, `back` = return to menu. Can also skip the menu entirely via a launch param: `rokubot launch dev --param demo=<id>` (see `DemoList.bs` for valid ids) |
+| `rendererTest` | Categorized, menu-driven suite of `BGE.Renderer` demos - deliberately **not** built on `BGE.Game`/`GameScene` (see `CLAUDE.md`'s "Manually exercising the Renderer" note for the architecture and how to add a new demo). Grouped by category on an on-screen menu. Every demo shows an automatic timing line (fps / frame ms / update ms / draw ms / draw calls), so this is the place to *measure* a draw-cost question rather than reason about it - the `quad-fill-benchmark` demo times two fill approaches head to head in one run. The Benchmarks category also has `occlusion-span-map-benchmark` (the occlusion span map's build/query cost) and `occlusion-scene-benchmark` (a scene of static occluders hiding objects, occlusion on vs off). | `up`/`down` = select in menu, `select` (OK) = run selected demo / demo-specific action, `back` = return to menu. Can also skip the menu entirely via a launch param: `rokubot launch dev --param demo=<id>` (see `DemoList.bs` for valid ids) |
 | `hybrid` | Fixed (was previously broken — stale `getImage` call). Now: SceneGraph side plays a sample video; roScreen/BGE side is a ball-to-target minigame that switches back to SceneGraph on collision. | Ball game: arrows move the ball, reaching the green target switches to video. `back` (either side) toggles/quits |
-| `terrain` | Demonstrates `BGE.DrawablePlane`/`SceneObjectPlane` (a Mode-7-style textured ground plane) — no vehicle/kart entity, just a camera driving around above the plane. Camera starts centered directly above the plane's origin. | `left`/`right` steer (yaw about world y), `up`/`down` drive forward/back along the current heading, `select` (OK) toggles the ground texture between the Mario Kart track image and a plain checkerboard, `options` (`*`) toggles the debug entity-details overlay, `back` quits |
+| `terrain` | Demonstrates `BGE.DrawablePlane`/`SceneObjectPlane` (a Mode-7-style textured ground plane) — no vehicle/kart entity, just a camera driving around above the plane. Camera starts centered directly above the plane's origin. | `left`/`right` steer (yaw about world y), `up`/`down` drive forward/back along the current heading, `select` (OK) toggles the ground texture between the Mario Kart track image and a plain checkerboard, `options` (`*`) toggles the debug entity-details overlay, `back` quits. In the start scene (`WorldScene`) OK instead toggles occlusion culling, and holding Back 2s also shows the occlusion overlay (occluders and hidden objects); a static chapel stands in the scene and hides the trees behind it |
 | `rpg` | "Broadsword" (manifest title) - a *Link to the Past*-style top-down action RPG with a story: opens on a title screen (Continue/New Game), then a town with NPCs (Bram, Hilde's shop, a gate knight), a seven-room keep (goblins, a goblin king, the witch) and a sewer (rats), sword combat, hearts + coins HUD top-left. Deep links skip the title and disable saving: `--param scene=TownScene|CastleScene|SewerScene|GuardroomScene|StoreroomScene|BarracksScene|AntechamberScene|KingsHallScene|ThroneRoomScene|GoblinShowcaseScene` (the showcase now includes the witch) and/or `--param stage=0-8` (story checkpoint; stage 3 = knight wants a sword, 5 = met Mara in the keep, 6 = goblin king beaten, 7 = throne room with the witch's intro playing, 8 = town, witch defeated), `scene=CreditsScene`, plus `spawn=<id>`, `flags=`, `items=`, `peaceful=`, `open=`. Real-time fighting is too fast to play via rokubot - hand that to the user. Black screenshots here have so far always been capture failures (retry; see gotchas). | arrows (or analog stick) move, `select` (OK) swings the sword / talks / confirms in panels, `play` opens the inventory, `info` (options) toggles debug overlays (colliders red, SolidWorld walls cyan), `back` quits or closes a panel (gamepad: A/B confirm/cancel, Y inventory, stick moves menu focus, B never quits; rokubot can't press gamepad buttons) |
 | `loading` | Asset-loading demo: a menu of scenes that each load in `GameScene.onLoad()`. "Large local assets" loads every model in `pkg:/models/` plus three large PNGs under a loading screen with a frame-time readout, then lists faces/sizes; "Custom loading screen" builds a 24x14 tile grid a row per frame under a strip-style loading screen. The debug UI (FPS etc.) is on. "Remote assets" downloads two images, a textured d20 .obj and a sound from `baseUrl`, plus `https://picsum.photos/200` (no extension - its type comes from the response's Content-Type; roUrlTransfer follows picsum's redirect) (default GitHub `main`; or serve `examples/loading/remote-assets` locally with `python3 -m http.server 8000 --directory examples/loading/remote-assets` plus `baseUrl=http://<mac ip>:8000/` - macOS may block incoming connections, so allow it when prompted, or use `npx http-server examples/loading/remote-assets -p 8000`) and lists each file as `network` or `cache`; a relaunch should show every remote file as `cache`. "Failure" shows failed loads. A "Clear download cache" menu button resets it. `--param scene=LocalAssetsScene|CustomScreenScene|RemoteAssetsScene|FailureScene` skips the menu. | `up`/`down` + `select` in the menu, `back` returns to the menu |
 | `visualnovel` | "The Mutiny": a short sci-fi visual novel (title with Continue/New Game/Credits and "Endings found", then a background, two portrait cards, a typewriter text box and choice buttons). Saves to the registry (`bge-visualnovel`), which `--deleteDevChannel` doesn't clear - to see a fresh install, break into the debugger and run `r = CreateObject("roRegistry") : r.Delete("bge-visualnovel") : r.Flush()`. `--param node=<id>` (plus `flags=`/`items=` comma lists) starts at a node with saving off, e.g. `node=confrontation items=relayTap,navLog,accessRecord`. Pressing OK repeatedly plays through on the first choice each time and reaches an ending in about 60 presses. Ctrl-C into the debugger lags a second or two, so it's no good for catching a short loading screen. | `select` (OK) finishes typing / reads on / picks the focused choice, `up`/`down` move focus, `info` (`*`) or `up` while reading opens the backlog (`up`/`down` scroll, `back` closes), `back` returns to the title (quits from the title) |