Getting started with AI.Planner

I'd like to get started with using the AI Planner, and ran into a few troubles.

• My custom Heuristic won`t be found by the AI.Planner builder, though it can be selected in the UI, when I try to play the scene, I get Temp\PlannerAssembly\AI.Planner.Actions\Basic\BasicExecutor.cs(29,124): error CS0246: The type or namespace name 'BasicNeedsHeuristic' could not be found (are you missing a using directive or an assembly reference?)
• The otto project uses custom effects as effect of actions to update the needs, however in the newest 2.2 build of the project I can`t find any place to choose such special effects.
• How can I update traits in scripts? I would like to increase my needs based on timeDelta each tick, but the TraitComponent returns me an ITraitData instead of an ITrait object, which I can`t cast back on my BasicNeed trait.
• Is there any way I can return the success of an action in a Callback, lets say in case of a Navigation action where the path gets blocked?

 

First question - are you using AI.Planner 0.2.2-preview.1?

I'll answer your questions in order:

• I'm not sure when this change was made, but we started writing the fully qualified type name for the default heuristic. If in the inspector for your plan you don't see the full namespace, then you might be on an older version. One thing you could try is to put your heuristic into the AI.Planner.Actions.<YourPlanName> namespace. Also, have you looked at this page? https://docs.unity3d.com/Packages/com.unity.ai.planner@0.2/manual/CustomPlannerExtensions.html
• Otto has not been updated for some time and was built on an older version of the planner. We may come back to it to update it at some point, but for now, please use the other planner samples: https://github.com/Unity-Technologies/ai-planner-samples
• With ITraitData there is a GetValue/SetValue: https://docs.unity3d.com/Packages/c...ner.DomainLanguage.TraitBased.ITraitData.html
• Not directly from the callback, but if you are using an IEnumerator you could set a value on the object somewhere and poll that or maybe raise an event.

 

Thanks for your answers and clarifications. Yes, I am using the 0.2.2-preview.1 build

• The problem is not that I can't select the heuristic in the inspector, the problem is that Unity then complains that it can't find it. I'll have a look at the Extensions page, I must have missed that one so far.
• I did look at the newer projects, I only mentioned Otto because I wanted to know if there is a replacement of that functionality of having a custom function being called as effect. This would be very useful to implement conditional effects.
  
• I did manage to update the values, now, manipulating values by their string names just feels very unclean
• Thanks for your answer, I will have to do some more thinking in how to handle interrupted paths. I probably also have to think some more on how to handle blocked paths in the first place.

 

I got my custom heuristic to work, the trick was to make a .asmdef and throw the code in there

I am now trying to get some custom traits working, since I believe Traits referencing a game object will be a better way to change the values backing the trait, but I can't create the asset to connect to it like the 'location' asset. How do I make the asset and make it use the custom trait definition?

 

I do use ICustomTrait, and I do use an int ID, I did base it on the location trait. The problem however is how to create the matching trait asset that is mentioned in https://docs.unity3d.com/Packages/com.unity.ai.planner@0.2/manual/CustomPlannerExtensions.html I did create a trait asset with the same name, how do I connect the two?

 

I'm not quite sure I understand. The location asset definition has three properties, of which Transform is not blittable, but in actual use, Transform is the only field that can be assigned.
I tried to do something similar with gameObject, to save an ID, but the autogenerated code still includes a regular ITrait struct, instead of my custom definition.

Code (CSharp):

1.  public struct Self : ICustomTrait, IEquatable<Self>
2.     {
3.         public int ID;
4.         public GameObject Character
5.         {
6.             get => null;
7.             set
8.             {
9.                 ID = Character.GetInstanceID();
10.             }
11.         }
12.  
13.         public bool Equals(Self other)
14.         {
15.             return ID == other.ID;
16.         }
17.  
18.         public object GetField(string fieldName)
19.         {
20.             switch (fieldName)
21.             {
22.                 case nameof(ID):
23.                     return ID;
24.             }
25.  
26.             return null;
27.         }
28.  
29.         public void SetField(string fieldName, object value)
30.         {
31.             switch (fieldName)
32.             {
33.                 case nameof(ID):
34.                     ID = (int)value;
35.                     break;
36.                 case nameof(Character):
37.                     Character = (GameObject)value;
38.                     break;
39.             }
40.         }
41.  
42.         public override string ToString()
43.         {
44.             return $"My ID: {ID}";
45.         }
46.     }

 

I did try Unity.AI.Planner.DomainLanguage.TraitBased, Unity.AI.Planner.Domains, as well as my custom namespace, without success. An ITrait struct always gets generated.

Also, is there a way to have Custom Preconditions and Actions without wrapping them in a separate Assembly, since I'd like to reference my main code in them.

Is there a Reference what the diffierent namespaces are? There seems to be a UnityEngine.AI.Planner, Unity.AI.Planner, and AI.Planner.

 

I'm still having trouble with getting custom traits to work.
A few features I think would be nice to have in the AI planner:

• An description of assembly requirements would be nice to have in the documentation, especially since custom heuristics can be selected in planner assets when they are defined in other places, only on build they won't be found.
• Methods on TraitComponent to check, add, remove and modify traits directly, without any need to mess with strings and ITraitData.
• A way to specify a Trait Based Object as Actor of a DecisionController Instance, meaning it always has to be used as first object. This would greatly simplify any situation with multiple actors, which may need to access each others main object to plan interactions. This currently requires making a separate local ID object, checking that each and every time if it is the same ID on the actor object, leading to a lot of redundancy, making actions less legible.
• I would like a way to easily get data from the game into traits, without having to write custom traits. One way I'd imagine would be an ITraitable<MyTrait> interface that can be implemented outside of any assemblies. ITraitable would have a function OnLoadWorldState(MyTrait trait) in which you can write all the data to the fields of the trait you defined before, and then return it. This way you can have traits backed by your game objects without having to write all the get/set stuff and dealing with assemblies and custom traits. The assemblies are very impractical, if my custom trait referencing my main character class has to go into an assembly, pretty much my entire game code has to go in that assembly.

 

I've made a note about this on our Favro board. Thank you.

This is going away. Traits will be accessed directly by name and not through a TraitComponent.

Have you tried any of the World Query options on the Decision Controller? There is a "From GameObject" filter that will constrain to including a specific GameObject. I think that might work better than the local object.

Unfortunately, this isn't likely to be supported. As of now, for performance reasons and for use of multi-threading in jobs all types need to be defined explicitly. If we explore an "interpreted mode" for the planner in the future, then perhaps we can create a dynamic trait of some sort, but for now I wouldn't rely on this feature being added. Another possibility is that there could be a post-processing step that occurs for your own classes that can generate traits and provide some interop.

 

If I have a TalkToPerson action it takes two Agent objects, the first one must be the one on the planner, the second one can be any other character.
The problem is if my planner needs to have access for this to all Agent objects, and needs to know which one the planner itself is. Constraining doesn't help there.

The types would be explicitly defined in the trait, the interface I imagined would be only filling in those defined fields when called upon.
If I have a health component, I would like a trait with a health int field, the field being treated like it was a standard trait, until the planner loads the world state again. Then the trait should reload the health field from the health component. To my understanding this is pretty much how the location trait currently works.

 

Can you share a little bit more about this? Are these all NPCs or is one player controlled? What is the significance of having one of the agents as the first parameter (i.e. is there an effect that only happens for the first parameter)? I need to understand more about your model before being able to answer the question.

I misunderstood your original question. Ideally, the traits will be used for the actual data storage. With our next release this will be much more direct than our current approach, which is via TraitComponent. I'm curious why your custom trait would be referencing the main character and not the other way around of your game code referencing traits and setting data on those. Either way, we can consider some helper scaffolding in the future as we learn more about how developers continue to use the planner. Thank you for your feedback.

 

The idea is that I have identical characters A, B, C etc that have for example a socialNeed that can be reduced by talking to each other. I want to ensure that the planner A only plans talks between A and B or C, and not B talking to C, while planners B and C likewise ensure their actor is always involved in the action.

I would consider the traits a model of the data for the planner, not the actual data. The effects of an action are the predicted changes, the actual changes are applied during the function callback assigned to an action.
I absolutely want my data on a scriptableObject I can serialize, subclass and add whatever types I want without dealing with the restrictions of the traits. Also I very much want my main data classes not in any separate assembly.
Also many of the character data may be irrelevant for the AI, and thus should not be in the planner and clutter up things.

The model vs data abstraction also is absolutely necessary if the outcome is random. The action may assume the average damage dealt, or the average HP healed, but the action itself changes it by a random amount. Similarly, the effect may actually be applied over time, not instantaneously like the planner assumes.

I can also think of cases where a trait is actually already amalagmated information, for example a single number representing the strength of a whole squad, in which case the squad should be polled to provide a strength value for the planner.

 

Thanks for the additional feedback. We discussed as a team and our current thoughts are to introduce a default trait (e.g. 'Planner' or 'DefaultAgent') on a trait-based object that also has a decision controller attached when initializing state for that planner. You can then use this default trait in any of your actions.

Some of what you're mentioning is already supported with ICustomTrait (e.g. Location is an example of that). We're currently re-working quite a bit of how traits are serialized in preparation for DOTS workflow support, so let's revisit this discussion when that release is out.

Re: random values -- the planner supports probabilistic outcomes from a single action, but that is not something that you can configure without digging into code (i.e. cannot make use of this through the UI). If you were going to have random outcomes, then you'd likely want to model an expectation value (read: avg) for an action instead and/or have different actions. It wouldn't be good to try and include randomness in a custom action effect for the planner as it would adversely affect the cost/reward of taking an action. The planner might pick that route as an optimal path even though in reality there is a low probability of getting a high or low value. It would be okay, however, to apply randomness in your callback when modifying the world state after taking a planner action.

 

That sounds great.

My comment was mostly designed as an example where I would like to have my data in two places, once in the world, and once separately on the trait which syncs it from the world. I'm sure the DOTS workflow will help there in any case, as you can write an system there to sync it in an efficient way, instead of relying on many Update() functions writing stuff to the traits that slow down the game.

A few other improvements and features that came to my mind:

• Flag enums and appropriate comparators would be a nice addition
• Custom preconditions and custom actions that work only on selected traits, instead of the whole state array would be great, similar to how CustomRewards work currently. Best would be if they can take additional, selectable parameters like a float to make for example a precondition 'distance between two locations is smaller than x'