Max update rate when continuous

[guilhermelawless]

Building a map using SLAM and asking for continuous map updates through ROS2D.OccupancyGridClient puts a high load on the system as the updates are frequent.

Depending on the way the map is updated, could it be set to update only the differences from the last /map update?

If not, maybe a max update rate is the solution?

[rctoris]

Map differences are a hard thing to do client-side. If throttling the publish rate on the SLAM node is not possible, perhaps a throttle on the client-side might work? https://github.com/RobotWebTools/roslibjs/blob/develop/src/core/Topic.js#L34

[guilhermelawless]

That might be the preferable solution, although when SLAM is active it's easy to achieve 500MB+ in the rosbridge_server node.

(Is there any other place to ask this?) Has the continuous mode been tested? Does it need any more configuration than the option set to true? I ask this because I am having an issue where the first update is shown accuractely, but with subsequent updates it goes blank (black background). I then need to reload the page for it show correctly, the most recent and updated map. The issue then repeats.

How I tested:

1. Using the slam_gmapping tutorial to publish map updates, through a rosbag file at a 0.1 scaled rate;
2. The map used is quite large (1000x1000 at 0.5 resolution), I might try to find a smaller map if this is the issue;
3. The HTML is simply the "map.html" in the examples folder of this package, modified with a 'continuous : true' when instancing a grid client.

EDIT: While this was done, rviz could show map updates successfully.