Dynamic Object Tracking by phatboysh - 1

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A multithreaded implementation of Nition's Octree for Unity allowing for discriminatory object tracking with large numbers of moving objects.

Unity 2018.1.0f2MIT LicenseUpdated 64 days agoCreated on March 19th, 2019
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DynamicObjectTracking

A multithreaded implementation of Nition’s Octree for Unity allowing for discriminatory object tracking with large numbers of moving GameObjects.

Use of the point Octree system is comparable to using trigger colliders with hard coded switch or if else statements, however the objects tracked and the information receivers are easily selected at your discretion (no more sifting through enormous amounts of collider data). This is also a viable option for collision detection if you wish to escape PhysX (and spherical colliders can meet your needs). The primary benefit is getting optimized spatial calculations without interfering with anything you (or perhaps your users) are doing with trigger colliders.

Any number of agents can track up to 701 classes / fields of objects (a thru zz), and each field may contain any number of tracked objects. Although 701 different fields of tracked objects is likely beyond any need - additional fields can be added at runtime (see public methods).

Every field has its own distance threshold value defining when it registers other tracked objects. Once another tracked object registers, an event is published to the subscribers (typically an agent or a game manager) monitoring that object. The event publishes the registered GameObjects inside the threshold (GameObject[]) and their associated object field types (string[] “a”,“b”,“c”…).

Additionally, this package can be configured to forego Octree implementation and simply automate Unity’s Collider trigger configuration across your selected fields of tracked objects. Both the Octree and Trigger configurations produce the same discriminatory data - reported the same way - to monitoring agents. You can easily benchmark the two against each other. Choosing to have this system automate trigger configurations for you will obviously negate any benefits afforded by using the Octree implementation.

20k Tracked Objects - colliding only with objects with that are different in color - using no colliders or rigidbodies.

The above scene uses a collision method that simply sets object direction to it’s position minus the colliding objects position. Object scales are set to match their threshold size. This scene averaged 20 fps on a 15" Surfacebook. When scene sizes get this large, collision detection loses accuracy, but crucially - the main thread remains unblocked (unless you choose the Unity Trigger implementation).

Getting Started

The Empty WorldMonitors Component

To start tracking, add a WorldMonitors component as shown above. This component is added to every “tracker” - i.e. a GameObject that will track the movement of a selected group of GameObjects. The + button will open up the Tracked Field, where you can add tracked objects. Add at least one more Tracked Field (in any instance of WorldMonitors) where the tracked objects will raise conflict with objects in other Tracked Fields.

Any number of WorldMonitors can be used. If multiple instances of WorldMonitors will be tracking the same object, that object must appear under the same field for every instance of WorldMonitors tracking it. See how PinkSphere (1) appears in the following (separate) instances of WorldMonitors - it is under “Set B” for each instance. The order of objects in Set B can be different for each WorldMonitors instance. Also note that the threshold sizes are the same for each field; this is enforced by the custom inspector code every time a value is changed so you won’t need to check across all instances of WorldMonitors for continuity.

Multiple WorldMonitors Instances - Use Symmetrical Fields


The WorldMonitor Component - Singleton

If you do not add this component it will be created for you, however you should make a sincere effort to set the parameters beforehand. Failing to do so can result in an unnecessarily large Octree which can consume resources. Place it on any GameObject you’d like.

This system will never use more than one auxilliary thread. If you wish, you may restrict the object tracking to the main thread at the expense of performance.

The exhaustive calculation is intended for benchmarking - however if you are using a very small number of tracked objects, exhaustive calculations may be faster for your use case. This method raises the conflict event every frame, as such it’s functionality is similar to OnTriggerStay(). It is of no value if you choose to implement the system’s automated Unity Trigger configuration.

Events

All events use the ObjectConflictHandler delegate

delegate void ObjectConflictHandler(GameObject objectWithConflict, GameObject[] conflictingObjects, string[] conflictingTypes);

  • GameObject objectWithConflict: this is the object who’s threshold has been crossed
  • GameObject[] conflictingObjects: an array of the objects who’ve crossed into the threshold
  • string[] conflictingTypes: an array of the object field names (e.g. “A”, “B”, “C” etc)

It is possible for more than one object to cross thresholds during an Update cycle, as such the latter two arguments are arrays.

ConflictEnterers(GameObject objectWithConflict, GameObject[] conflictingObjects, string[] conflictingTypes)

Subscribe to this event for notification every time a tracked object enters another’s threshold.

ConflictLeavers(GameObject objectWithConflict, GameObject[] conflictingObjects, string[] conflictingTypes) ConflictEnd(GameObject objectWithConflict, GameObject[] conflictingObjects, string[] conflictingTypes)

These two events are mutually exclusive; subcribe to ConflictLeavers if you need an update every time an object leaves another’s threshold area. ConflictEnd is only emitted when all tracked objects have vacated a threshold area.

Public Methods

void ChangeThresholdSize(float threshold, GameObject trackedObject, string objectType)

  • float threshold the new threshold size you wish to set.
  • GameObject trackedObject (Optional) the particular tracked object whos threshold you wish to change.
  • string objectType (Optional) the field name of the threshold you’d like to change

Remarks: you must include at least one of the optional arguments - - both options change the threshold size for an entire field, not individual objects. If you are using the trigger implementation, use the public ChangeTriggerSize() method instead.

void InsertNewTrackedObject(GameObject trackedObject, WorldMonitors owner, string objectAffiliation, float threshold)

  • GameObject trackedObject: the object to be tracked.
  • WorldMonitors owner: the WorldMonitors component for the tracker tracking this object.
  • string objectAffiliation the type (field name) for this object. This can be anything – here is where you can expand on the 701 field limit.
  • float threshold: the new threshold size you wish to set.

Remarks: see the example scenes for demonstration of usage.

void RemoveTrackedObject(GameObject trackedObject, WorldMonitors whoToRemove, bool retainOtherTrackers)

  • GameObject trackedObject: the tracked object to be removed.
  • WorldMonitors whoToRemove: (Optional) you can remove individual trackers from tracked objects as they can be tracked by any number of agents
  • bool retainOtherTrackers: (Optional) set this argument true if you wish to remove only aspecified tracking agent.

Remarks: you should always remove the WorldMonitors owner when an agent is destroyed, or at the minimum unsubscribe from the events. see the example scenes for demonstration of usage.

Tracker - an Example Object Tracker

You will find the Tracker class in the example scenes, which demonstrates how to use all of the public methods except for ChangeThresholdSize(). The last Tracking Agent in the heirarchy (in both scenes) is preconfigured to use some of the options.

** Scenes **

TrackingExample


TrackingExample demonstrates the system's large scale dynamic object tracking ability, and an example method is used to change the tracked object's trajectories when conflicts are incurred by one enabled object (you can enable this behavior in the Tracker inspector). This scene includes 500 initial tracked objects and inflates to 5,000 at runtime. All of these object's are configured to interact with thresholds beyond their size (like a trigger). On a SurfaceBook (i7, GTX 1060), this scene runs at 45 fps with the tracking system updating once 1-2 times per 10 frames (note the tracking refresh rate on smaller scenes is about once/ frame).

SmallTrackingExample


This scene is preconfigured to log events to the console so you can quickly understand how and what data is published.

Important Points

If you may be switching between the Octree and Trigger tracking methods, you should be aware of how the threshold and trigger radius differ. They are both a measure of the same thing (a spherical radius) however triggers emit collisions when the triggers cross each other’s boundaries, not when the parent object crosses the boundary. You can configure the WorldMonitor component to have triggers immitate the Octree behavior or visa-versa. The difference between the two methods without configuring the WorldMonitor to immitate behaviors is shown below.

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