I am currently working on an AI system in Unity for a stealth game but where the enemies are those that infiltrates and the player has to defend a specifc location, for example an object the enemies will try to steal. I wanted AI agent to act like I am when playing such a game, like hiding behind walls, hearing enemies footsteps, flee when an enemy is coming closer. I wanted my AI agent to have the same information as a real player. In a game there is mainly two information sources : what we see and what we hear. This article concerns the first source. How to give the AI agent a way of knowing what it sees.

Unity gives many ways of analysing the game world. It has functions like Physics.RayCast(...) or Physics.OverlapSphere(...), it gives us also information about bounds, meshes and renderer. For my project, AI agents must be able to look for places to go, to have access to all objects they see and are interested in. 

As I was thinking about what's a view, and how to give it to an AI agent, I was considering what are the view properties, it has a field of view, a facing direction, an origin and how far we see. I realised that this description is a good description of a camera. So why should I make a camera-like component if I can try using the existing Unity camera component.

I tried to figure out if there was a way to know every gameobject present in the line of sight of the camera in Unity. There is, but it is too time and memory expensive (I'll be happy to show you how). There are other information you may think of using like using renderer.isVisible, OnBecameVisible(), OnWillRenderObject() but you'll have to attach a script to every object you want your AI to be able to see. Besides, renderer.isVisible doesn't tell you from which camera it is visible, and none of these method takes care of occlusion. All these datas are hard to work with knowing we are working with mutliple camera. 

My idea is to attach a camera on every AI agent, a viewsensor. The camera is set with a certain field of view, and a far plane.  Unity has two handy functions for camera testing, the first one gives back the 6 planes defining the camera frustum, and the second one tells if a bounds object is inside or outside the camera frustum.

Now we can know if a gameobjet is inside our view but not if we can see it because it may be hidden by another object closer the camera position. So I use linecasts to know if we can see the object. But to which position should I cast? Object center position is a good choice but not necessarily accurate enough. I use the object mesh bounds, and go through all the bounds positions and stop when a linecast don't go through anything and then I know a see the object. 

The perfect way would be to do a linecast between each vertice of the mesh but it would be too much time expensive.

Now we have a function telling us if a specific object is in AI line of sight, I just test every object given by an overlapping sphere check starting on the camera position and with a radius of my camera far plane distance. I call my previous SeeGameObject function on each object and keep those are in line of sight in an array.

Each connector, that means each gameobject you want to use in an electronical circuit, must have a script component that derives from the BaseConnector script. At any time, such a gameobject can know if its signal is activated by accessing the connector component and by reading its Activated property which is a boolean value. Besides, everytime the signal changes, the gameobject receives a message that calls any OnReceiveFromConnector(bool b) methods he has on its scripts. The boolean b tells us if the signal is on or off. So there is no need for you to check the Activated property at each frame since every time this property changes you get a call of the OnReceiveFromConnector(bool b) function.

Any connector comes with an empty public gameobject property that you can set in the editor. You can put here any gameobject you want. This gameobject will now receive the OnReceiveFromConnector(bool b) mehtod call too. It can be usefull when you don't want a gameobject to be part of a connector hierarchy but still have notification of changes from one of them.

If you look in the package there is a connector called LoopConnector, and if you look on any connector, you can see a public list of loop connectors you can set in the editor. This connector lets you make loop on your circuit and also let you send a signal received on a specific circuit to another circuit. To do so, you just have to add the Loop connector gameobject to the loop connectors list from where you want the signal to be sent. The signal will be received by the loop connector and will be its signal value.

Input connector are connectors that don't process their children signals. By default, if you create a new connector, it will not take into account its children and will be an input controller. For example, the loop connector is an input connector. To process children signals, you just have to override the OnReceiveFromChild(bool activate) method in your script.

I think you can do lots of thing with this package. Here are some ideas in which I would use it:

• Button system to have a complexe system to open doors, switching lights, etc...
• Dialog system to unlock dialog options
• Quest system to make multiple way to achieve a same quest
• Crafting system to have complex recipes
• Simply for an electronical circuit and to be as creative as some minecraft redstones players !

This is the base class for connectors.

It's a little project I had to make as part of a school Serious Game project. It was made in Unity at the time where Unity didn't have a real 2D mode so I used an external package I found on the Unity Asset Store which is called Orthello2D.

This project contains a homemade crossword algorithms, working on a short given list of words. It's not making real complete without-gap crossword at all, because these one works with big database of words and take quite a time to process. Here is juste an algorithm working with very few words but trying to make the best it can to cross these words together.

The source version you can download below is a rebuild version of it on Unity 4.3.4. It works fine on my computer.

You can test the generator just by opening the CrossWordsGenerator.unity scene in Unity and play it in the editor. As this application comes from a bigger project, it comes with loading and saving functions from files and creates the crosswords using the crossword.txt file that contains the words and their clue to guess them.

My algorithm is not extraordinary at all, but give acceptable results. It doesn't assure at all that all words will be on the grid. But it makes its best to have a maximum of words on it.

Here is how it works:

• Sort the words list by length (descendant)
• Put the first (= biggest) word of the list on the grid
• Loop on all the words in the list
• For each word of the list, find letters in common with words letters on the grid, that gives you a list of potential position
• Remove from this new list all positions that "if you place the new word there, it will overlap existing words" on the grid. Except if overlapping letters are both equal.
• Choose one of this position to place the word on. 

That's of course the very basic process but it takes others parameters to be more precise.

That's some features I added:

• To choose which position to place the new word, I use a score system to find the best position. This score is based on several parameters like: How many intersections it will create with existing words, How much it will increase our grid (the less the better), or little random fuzzer...
• Not always sorting the words lists by length, but shuffling instead
• Since we have some random parameters, one list of words won't give us always the same grid. So when generating a grid, I generate a certain amount of them and choose the best, that has the more words and the smallest size.

To work with words easily I make a class that has position and grid features called CrossedWord. The algorithm code is not clean at all, and contains lots of variables strangely named, sorry about that. I let you have a look at it:

This tutorial shows how to have an android app communicating with an android unity application. It also shows how to communicate between the android java app default code and unity. I had to do such a thing a year ago for one of my teacher that wanted to process data from an external accelerometer directly into unity. He already had an custom android app he made, that can receive these data but no way to send them to a unity game.

I'll assume you already made some android app. For simplification, I won't speak about in default android app creation but just tell you what you need to know to get this done.

There is a simple way to send data from a standard app to another one and it's called a Service. Basically, a service is something inside an app that can broadcast data to any other app that is configured to listen to it. It's a standard android class coming from android.app.Service that can be derived to be used in your app.

Let's have a look on how to that:

• First of all, create a new class inside your sending app, deriving from android.app.Service. This class is the service that will send an Intent to the others apps.
• Now you have to make your service running inside your app. To do so, you can start the service in any Activity simply by using startService(new Intent(this, MyService.class)); where MyService is the name I called my new service derived class.
• When you start it, a new instance of the service is created and directly call its onStart method.
  

Here's an example of a really simple service, using an Handler and sending data each second. All instructions are commented for you to understand how it works:

• You must now modify the AndroidManifest.xml file to let Android know this app has a service in it, otherwise it won't work. So you just have to add this line under the <application> section:

We will see now how to receive the data our sender sends us. As this receiver is made for Unity, it has no activity, and work as a plugin for Unity. 

That's what you must do:

• Create a new android app without any activity
• Make a derived class of android.content.BroadcastReceiver

Here's an example code that explains the nexts parts:

• Compile it as a .jar file. Using Eclipse you can do it trhough Eclipse -> File -> Export -> Java -> Jar File, press next, check your project, uncheck all boxes in the right panel, uncheck jar compression, choose a destination file and press done.

Unity has been made to be able to use external library in a very simple way.

• Create this hierarchy of folders using the default Asset folder: Assets/Plugins/Android/ 
• Move your .jar file in it

Now, we have to modify the AndroidManifest.xml Unity uses to add some specifications for our receiver plugin to work properly. The easiest way to get this file is to build our Unity project to run on Android. When we build it, Unity create a manifest during compilation, that can be found in the Temp folder of our project. Copy it and move it next to the .jar file in the Android folder.

• Modify the manifest by adding these lines under the <application> section:
  

After <receiver android::name=... you have to add the exact and full location of your Receiver class inside your plugin package. And after <action android::name=... comes the name of the Intent you want to listen at. It must be the same as what you wrote in the Sender in the sendIntent.setAction(...) method.

Everything is set up now for us to be able to receive data of an other app inside a Unity application. We just have to see now how to use it in a Unity Script:

We're done ! I hope you get all the necessary information to have this working for you. Don't hesitate to ask me if you have any questions or problems. I'll be very happy to help you !

I would like to thank Simon Philippe, a friend of mine, for having worked with me on this code.

As usual, excuse me for all my English mistakes, I'm not a native speaker.