Add "id" to autoware_perception_msgs/msg/DetectedObjects.msg

[felixf4xu]

Hi,

In our case, when receiving DetectedObjects (autoware_perception_msgs/msg/DetectedObjects.msg), it difficult to tell one object from the rest of others, in our workaround, we need to add an id to the message definition based on the index in the array of DetectedObjects. In this workaround, we need to create a struct with id and copy the msg to the newly created struct.

I'd like to see if it's possible to update the msg definition and add an id field to it.

Thanks.

[mitsudome-r]

Could you clarify more on why you want to add id in a bit more detail?
In general, DetectedObjects won't have an id set to each object because the objects are not tracked within the detection modules, and you can just use its index within an array to know which objects you are referring to. Once the detected objects goes through the tracker modules, there will be object_id attached to the output information so that users can link the same objects between different messages over time.

[felixf4xu]

Maybe we are lazy, sometimes we don't use tracking/fusion, in that case, we use DetectedObjects directly.

[NickYang-Turing]

If you need an "ID" in DetectedObjects, I recommend considering the order of the vector as the "ID." For example, .at(0) could correspond to ID = 0. However, assigning an ID in this way may not be meaningful because the order of detection is typically based on the object's range, meaning that the ID will change dynamically when a new object appears. This is one reason to use a tracking system—to consistently identify an object across timestamps, allowing us to recognize that an object at the current timestamp is the same as the object in the previous timestamp.

[mitsudome-r]

I agree with @NickYang-Turing on this.

If you need an id for DetectedObjects, then you should just use the index of the array. However, it doesn't guarantee that the objects will be ordered in the next message so you should use tracking modules if you need to track an object over time.