Character Trait Model: How Unhappy Is Unhappy

Modelling character traits can be tricky: an example problem has been presented by Jon Ingold in this GDC talk. I discuss the problem below and present a sample model that solves it. I provide an implementation in a C# class.

For character trait one may think of say the character happiness, or a relationship-with-X trait.

The problem is presented from minute 36 of the talk: the first idea that comes to mind in modelling a character trait is by using a number. Greater the number, better the state of the trait. This doesn’t work very well.

How Unhappy is Unhappy

From Jon Ingold GDC talk.

Then Ingold quickly jumps to a proposed solution, which consists in tracking two numbers, positive and negative experiences:

Unhappy vector

From Jon Ingold GDC talk.

Apart from the fact that changes are modelled more appropriately using two variables, what was exactly the problem with using one number?

Here is how I understood the problem: suppose you want to model the happiness of a character in a gameplay. You say that the variable HappinessLevel determines HappinessState according to these values:

HappinessLevel >= 5 = VERY_HAPPY
0 < HappinessLevel < 5 = HAPPY
-5 < HappinessLevel <= 0 = SAD
HappinessLevel <= -5 = SUICIDAL

The character goes through many episodes in two different game-plays: in one the character has 2 positive episodes, and 8 negative ones, and so goes SUICIDAL: 80% of the episodes were negative.

In another gameplay, the character has 20 positive episodes and 25 negative ones. Character is still SUICIDAL, but actually only  55% of episodes were negative! Something clearly does not work :-(

Taking the hint from the talk above, I’ve implemented a generic class model for Character Trait that considers the whole set of the episodes. The set of states and their level can be injected; moreover you can have a “decay %” so that for each new episode, all previous ones have a decay, so older the episode less relevant it gets :-) (by default decay is 1 so its turned off).

You find the class and a test (for Unity) in this zip. It can clearly be refined ad infinitum in function of specific needs, e.g. having episodes that are both positive and negative and so on.

A couple tests:

First test no decay test 1 output
Second test with decay Log with decay

Thanks to Daniele Giardini for campaigning for LINQ removal from the code.

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Tips For The Pragmatic Unity Developer

In the video below I’ve presented several productivity tips / hacks for the great Unity3d developer, that cultivates his / her essential qualities (impatience laziness hubris):

 

Sources & References

The three most essential plugins are DOTween, Text Mesh Pro and Console Pro.

Jet Brains IDE for C# preview here.

The “auto-save on play” script is here, The “no more hot reload script” is here, both by the same cool guy.

The scene object enable and disable script is this:

public class TheScene : MonoBehaviour
    {
        public GameObject[] activateOnStartup, deactivateOnStartup;
        
        void Start()
        {
            foreach (GameObject go in activateOnStartup)
            {
                go.SetActive(true);
                if (go.GetComponent<CanvasGroup>() != null)
                    go.GetComponent<CanvasGroup>().alpha = 1;
            }
            foreach (GameObject go in deactivateOnStartup)
            {
                go.SetActive(false);
                if (go.GetComponent<CanvasGroup>() != null)
                    go.GetComponent<CanvasGroup>().alpha = 0;
            }
        }
    }

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Untangling GameObject State in Unity

In this short post and video I try to discuss and clarify a few points about GameObject state in Unity with respect to game, scene and “runtime” scope. It is a bit more complex than one may understand initially, so bear with me a little.

When you start developing scenes in Unity, it won’t take long before you start asking questions like:

How can I get the same GameObject in different scenes?

Why do static properties sometimes get reset across scenes?

Why when I reload a scene I get duplicated objects which are meant to be singletons?

How can I comply with the (highly practical) principle “Make the game runnable from every scene” when I have global instances from other scenes?

Here are some answers.

Here is the full schema I refer to:

GameObject State in Unity

While MonoBehaviour’s  life-cycle is quite well documented e.g. both directly in Unity docs here and also by third parties e.g. here, how to handle GameObject’s persistence in and across scenes may be more obscure.

So here are written (partial) answers to the questions above:

How can I get the same GameObject in different scenes?
Would be probably better to reword this as “how can I persist and share data across scenes” – and there are many ways to do that :-)

Why do static properties sometimes get reset across scenes?
Only static properties which are GameObjects present in the scene will get reset (typically singletons). Other static properties will be preserved across the virtual machine.

Why when I reload a scene I get duplicated objects which are meant to be singletons?
That is because you marked those objects with DontDestroyOnLoad and created them (also) in other scenes. Create them via code (not in hierarchy) checking before their existence.

How can I comply with the (highly practical) principle “Make the game runnable from every scene” when I have global instances from other scenes?
This is best done just as explained above: create the global objects in every scene via code if they don’t already exist.

 

Unity Execution Order

Unity Execution Order – from Unity documentation.

If you are in need of learning some good patterns in software game development, a really nice book is Game Programming Patterns. Here are also 50 Tips for Working with Unity (Best Practices) which I reread from time to time, understanding progressively more and more of them (but still not all :D).

Thanks to Daniele Giardini for some feedback on the state scheme above.

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A note of the wild use of “if(object)” in Unity’s C# code

Looking at other people’s C# code for Unity, I kept seeing this bizarre usage of if:

if (object) { …}

where object was a real object, not a bool instance. This is a JavaScript kind of usage, where there is a big (perceived) mess about object and value types, so I wondered how did C# “automagically” cast to bool? You cannot do that in classical typed OOP languages like Java.

Turns out there is nothing about this in C# itself, its MonoBehaviour that implements implicit boolean casting

public static implicit operator bool($classname$ me){
return me != null;
}

Actually you will have to navigate the hierarchy up to Unity’s Object to find it. See also here.

But if you are learning C# with Unity, be careful as “This can be really confusing because that behavior doesn’t carry over when you start using standard .net libraries and other 3rd party code that is agnostic to Unity.” – here.

And neither it will when writing your classes, when not extending MonoBehaviour, so its not a healthy habit to catch.

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A note on slimy static Unity3d gameObject instances

A quick note on the state of C# static variable instances in Unity3d.

So I just discovered that static properties of classes extending MonoBehaviour on level reload may get reloaded or not, depending on circumstances.

The problem is this: you may need in your game development to have a singleton manager class instance which is also a game object. [Read more…]

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