Let a deployment turn the camera on

README.md

@@ -183,6 +183,30 @@ docker run --rm -p 8642:8642 -p 9002-9202:9002-9202/udp \
   -v $(pwd)/build/city/tiles:/world:ro -e SKYSIM_TILES=/world skysim
 ```
 
+`docker-entrypoint.sh` turns `SKYSIM_*` variables into flags: `SKYSIM_API_BIND`,
+`SKYSIM_API_PORT`, `SKYSIM_VEHICLES`, `SKYSIM_TILES`, `SKYSIM_STREAM_RADIUS`,
+`SKYSIM_STREAM_MAX`, `SKYSIM_DT`, `SKYSIM_TIME_MODE`, `SKYSIM_SPAWN_HOME`, and
+`SKYSIM_EXTRA_ARGS` for anything not listed.
+
+**Set `SKYSIM_TIME_MODE=interactive` on a long-lived server.** The default is `strict`,
+which is what determinism and CI replays need — a barrier every tick, and an abort when
+a vehicle misses it. A server that vehicles join and leave wants the opposite, or one
+lagging aircraft takes the fleet down with it. Match `SKYSIM_DT` to the scheduler rate
+the vehicles are launched with, too: in lockstep, physics faster than the autopilot's
+loop means most ticks miss their deadline.
+
+**`SKYSIM_CAMERA_FPS` is the camera switch.** Without it no frames are rendered and
+the camera endpoints serve nothing, whatever else is set. With it, `SKYSIM_CAMERA_SIZE`
+(default `256x144`), `SKYSIM_CAMERA_QUALITY`, `SKYSIM_CAMERA_THREADS`,
+`SKYSIM_CAMERA_FOV`, `SKYSIM_CAMERA_PITCH` and `SKYSIM_CAMERA_RANGE` apply:
+
+```bash
+docker run --rm -p 8642:8642 -p 9002-9202:9002-9202/udp \
+  -v $(pwd)/build/city/tiles:/world:ro -e SKYSIM_TILES=/world \
+  -e SKYSIM_CAMERA_FPS=10 -e SKYSIM_CAMERA_SIZE=256x144 skysim
+# http://localhost:8642/instances/0/camera.mjpg
+```
+
 ---
 
 ## Control plane (`--api-port`)

docker-entrypoint.sh

@@ -8,6 +8,16 @@ set -euo pipefail
 
 args=(--api-bind "${SKYSIM_API_BIND:-0.0.0.0}" --api-port "${SKYSIM_API_PORT:-8642}")
 
+# One mapping, used by everything below: set the variable, get the flag; leave it
+# unset and the binary's own default stands, so a default lives in one place
+# rather than being restated here.
+add_if_set() { # env-var-name flag
+    local value="${!1:-}"
+    if [[ -n "$value" ]]; then
+        args+=("$2" "$value")
+    fi
+}
+
 # Vehicles are normally spawned on demand over the control plane, so default to
 # starting with none rather than skysim's built-in default of one.
 args+=(--vehicles "${SKYSIM_VEHICLES:-0}")
@@ -24,12 +34,31 @@ if [[ -n "${SKYSIM_TILES:-}" ]]; then
     fi
 fi
 
-if [[ -n "${SKYSIM_DT:-}" ]]; then
-    args+=(--dt "${SKYSIM_DT}")
-fi
+add_if_set SKYSIM_DT --dt
+
+# Time mode, which a deployment could not set at all before.
+#
+# skysim defaults to strict because that is what determinism and CI replays need:
+# a barrier every tick, and an abort when a vehicle misses it. A long-lived server
+# wants the opposite — vehicles join and leave, some of them lag, and none of that
+# should take the fleet down. Without this the only way to say so was
+# SKYSIM_EXTRA_ARGS, so every deployment quietly ran strict.
+add_if_set SKYSIM_TIME_MODE --time-mode
+
+add_if_set SKYSIM_SPAWN_HOME --spawn-home
 
-if [[ -n "${SKYSIM_SPAWN_HOME:-}" ]]; then
-    args+=(--spawn-home "${SKYSIM_SPAWN_HOME}")
+# Camera. SKYSIM_CAMERA_FPS is the switch — without --camera-fps the render
+# service is never built and every other camera setting is inert, which is
+# exactly how a deployment ends up serving a control plane with no pictures on
+# it. The rest only apply once it is on.
+if [[ -n "${SKYSIM_CAMERA_FPS:-}" ]]; then
+    args+=(--camera-fps "${SKYSIM_CAMERA_FPS}")
+    add_if_set SKYSIM_CAMERA_SIZE --camera-size
+    add_if_set SKYSIM_CAMERA_QUALITY --camera-quality
+    add_if_set SKYSIM_CAMERA_THREADS --camera-threads
+    add_if_set SKYSIM_CAMERA_FOV --camera-fov
+    add_if_set SKYSIM_CAMERA_PITCH --camera-pitch
+    add_if_set SKYSIM_CAMERA_RANGE --camera-range
 fi
 
 if [[ -n "${SKYSIM_EXTRA_ARGS:-}" ]]; then