Toggling lidar sensors causes fps drop

[mozhoku]

Toggling lidar sensors causing fps drop in the simulator. It is not consistent with the FPS drops. Topics stop and removed properly from the Rviz side when toggled.

I also had problem with removing publisher topics after destroying the related component. After looking a bit more into the code I saw a part saying that GC should take care of it by default. It was inconsistent with removal of the dead topics. So I had to call GC manually after disabling the sensors. I'm suspecting a similar issue with the lidars but I'm not sure. I tried calling GC after removal of the RGLLidarPublisher but couldn't see any difference.

Since lidar simulation works different from the other sensors in the simulation, I'm kinda stuck here. I'm not really experienced about GPU side of the stuff so any help would be appreciated :pray:

Here is the video showing the issue:

• https://youtu.be/OguyhREBRbk

Script responsible for toggling the sensors (part related to lidars is in between lines: 16-33):

• https://github.com/autowarefoundation/AWSIM-Labs/blob/main/Assets/AWSIM/Scripts/UI/SensorToggleFunctions.cs

Current RGLLidarPublisher and LidarSensor scripts:

• https://github.com/autowarefoundation/AWSIM-Labs/blob/main/Assets/AWSIM/Scripts/Sensors/LiDAR/RglLidarPublisher.cs
• https://github.com/autowarefoundation/AWSIM-Labs/blob/main/Assets/RGLUnityPlugin/Scripts/LidarSensor.cs

@WJaworskiRobotec @lchojnack

[msz-rai]

Hi @mozhoku

Thank you for reporting the issue.

The FPS drop when toggling LiDARs may be due to their desynchronization and the need to update the scene to RGL (library for LiDAR simulation) more frequently. This update is an expensive operation, especially when skinned meshes are on the scene (mesh skinning is performed on the CPU). When starting the simulation, the timers of the LiDARs are initialized identically. On each FixedUpdate() the timer is incremented with Time.deltaTime and the check whether to trigger the sensor is performed. Before each LiDAR trigger SceneManager updates the scene to RGL. If all of the LiDARs trigger on the same "frame" there is only one scene update needed (the best case for FPS).

When LiDAR is disabled its timer is not updated. After its activation, its timer will not be synchronized with other LiDARs (unless activated at the right moment, but that is unlikely) and there will be additional scene updates needed.

If my assumptions are correct, the quick workaround would be to copy the timer value from the timer of any other active sensor in the OnEnable() method.

[msz-rai]

@mozhoku

Regarding removing publisher topics, the code in OnDestroy() method should destroy publishers immediately.

[mozhoku]

@msz-rai Thank you for the reply :pray: I'll try to keep their timer values in sync.

@mozhoku

Regarding removing publisher topics, the code in OnDestroy() method should destroy publishers immediately.

This is true for the lidar publishers, they remove their topics OnDestroy() immediately. But for other sensors I have to call GC manually in their OnDestroy() method.

It says in the: https://github.com/autowarefoundation/AWSIM-Labs/blob/6c37af514407c3192b20a47a1c610fe323496daa/Assets/Ros2ForUnity/Scripts/ROS2Node.cs#L23C4-L27C19

/// A class representing a ros2 node. Multiple nodes can be used. Node can be removed by GC when not used anymore,
/// but will also be removed properly with Ros2cs Shutdown, which ROS2 for Unity performs on application quit
/// The node should be constructed through ROS2UnityComponent class, which also handles spinning

Edit: Just realized, the way I said sounded like RGLLidarPublisher has problem with OnDestroy(). Sorry :pray:

[mozhoku]

It was just as you said @msz-rai . Thanks a lot :+1:

Here is the video with synced lidar timers: https://youtu.be/NL3mylAa7zI