docs: describe moving Nav2 observation demo

Signed-off-by: SamuelFoo <fooenzesamuel@gmail.com>

Author: SamuelFoo

discourse/3-layered-global-occupancy-map.md

@@ -24,7 +24,7 @@ observations, can be added later.
 * The Rust map server composes a static occupancy grid and active observations
   into `/map`
 * The Nav2 demo converts scans from three robots into point regions and displays
-  the combined map
+  the source contributions and combined map
 * The observation messages live in `rmf_layered_map_msgs`, leaving
   `rmf_prototype_msgs` unchanged
 
@@ -126,32 +126,32 @@ occupied space is not accidentally erased by another active source.
 
 # Three-Robot Nav2 Demo
 
-The launch file starts three stationary robots in different free corners of the
-warehouse and spawns one deterministic Gazebo box near each robot. Each
-observation node subscribes to its robot's local `sensor_msgs/LaserScan`,
-filters invalid or out-of-range returns, and publishes the remaining scan
-endpoints as point regions.
+The launch file starts three robots in different free corners of the
+warehouse, cycles them through fixed Nav2 goals, and spawns one deterministic
+Gazebo box near each robot. Each observation node subscribes to its robot's
+local `sensor_msgs/LaserScan`, filters invalid or out-of-range returns, and
+publishes the remaining scan endpoints as point regions.
 
-Each scan is a replacement snapshot: `reset_source` removes the source's
-preceding points before the new points are added, and a short TTL removes the
-source if it stops publishing. The observation-frame pose is recorded in the
-shared `map` frame so the map server can transform the scan-local regions before
-rasterizing them.
+Each scan is added to a rolling observation history until its TTL expires. An
+update may set `reset_source` so the new scan replaces all active observations
+from that source instead of being added to its history. The observation-frame
+pose is recorded in the shared `map` frame so the map server can transform the
+scan-local regions before rasterizing them.
 
-The demo launches Nav2 localization but does not launch Nav2 planning or control
-components, RMF planning, or navigation goals. Three robot-local RViz windows
-are enabled by default, and another RViz window displays the combined global
-`/map`.
+The demo launches Nav2 localization, planning, and control for the fixed goal
+loops, but does not launch RMF planning. Robot-local RViz windows show Nav2
+state, while another RViz window displays the combined global `/map`. The
+combined view overlays incoming region updates as colored markers grouped by
+source, with the same retention behavior as the map contributions.
 
 The scan-to-region conversion is deliberately simple so its information loss
-and publication cost are visible. `beam_stride` reduces the number of point
-regions, `publish_period_sec` throttles replacement snapshots, and
-`max_observation_range` limits represented returns. `ttl_sec` controls how
-quickly stale snapshots expire. Each publisher logs its number of input beams
-and output regions so message density, update rate, and visual fidelity can be
-compared. The current demo publishes occupied endpoints only; it does not
-convert raycast clearing into free-space regions or compress adjacent points
-into larger regions.
+and publication cost are visible. Scan sampling reduces the number of point
+regions, publication throttling limits the snapshot rate, and the observation
+range limits represented returns. The TTL controls how quickly stale snapshots
+expire. Each publisher logs its number of input beams and output regions so
+message density, update rate, and visual fidelity can be compared. The current
+demo publishes occupied endpoints only; it does not convert raycast clearing
+into free-space regions or compress adjacent points into larger regions.
 
 # Example Flow
 
@@ -187,3 +187,5 @@ The committed server and demo tests cover:
 * multiple robot sources being stitched into one composed grid
 * filtering invalid and out-of-range laser returns
 * preserving original beam angles when scan points are sampled
+* converting point and rectangle updates into source-colored markers
+* retaining markers until TTL expiry and replacing them on source reset

map_server/rmf_layered_map_server_demo/README.md

@@ -10,12 +10,22 @@ This demo publishes a synthetic static grid and a temporary rectangle with a fiv
 ros2 launch rmf_layered_map_server_demo demo.launch.py
 ```
 
+Use `use_rviz:=False` for a headless run.
+
 ## Three-Robot Nav2 Observation Demo
 
-This demo combines laser observations from three stationary Nav2 robots in the global `/map`:
+This demo combines laser observations from three moving Nav2 robots in the global `/map`:
 
 ```bash
 ros2 launch rmf_layered_map_server_demo nav2_observations.launch.py
 ```
 
-Use `use_nav2_rviz:=False` to open only the combined-map view. Use `spawn_clutter:=False` to run against the unmodified warehouse world.
+By default, the demo opens three robot-local RViz windows and one combined-map view, moves the robots between fixed goals, spawns demo obstacles, and retains scans for five seconds.
+
+* Set `use_nav2_rviz:=False` or `use_global_rviz:=False` to disable either RViz view.
+* Set `move_robots:=False` to disable robot movement.
+* Set `spawn_clutter:=False` to use the unmodified warehouse world.
+* Set `reset_source:=True` to show only the latest scan from each robot.
+* Use `map` and `params_file` to override the warehouse map and shared Nav2 parameters.
+* `beam_stride:=1` and `publish_period_sec:=0.5` control scan sampling.
+* `max_observation_range:=2.5` and `ttl_sec:=5.0` control range and retention.