Unity3D Boids script 2013

Readme.md

Introduction

Video: https://www.youtube.com/watch?v=QKNUkcMUD34

This code have not been tested since 2013, but the math in AgentBrain.js should work in any system. This script is just an experiment, it takes a lot of CPU and can only handle a few hundred agents.

This system works with Unity's collision system, so every argent has a collision sphere which is a "trigger zone" which is a lot larger than the agent it self. If other agents are inside this collision sphere they will be part of the crossAgent calculation. This area is how far each boid can see, and use this to look at the boids that are in close range to calculate a movment goal.

The brain script handles both player, pray and preditors AI. It works isolated on the agents without direct knowledge of other agents, so each agent have the brain script attached.

The spawner script is just added to an empty object to generate all the agents.

AgentBrain.js

#pragma strict

// Customizable
var detectionRange : float = 25.0; // Set from spawn script
var updateSkip : float = 5.0;
var aSpeed : float = 70;
var hostile : boolean = false;
var player : boolean = false;

private var curVec : Vector2 = Vector2.zero;
private var instructionUpdate : int = 0;
private var lastAngle : float = 0;
private var lastSpeed : float = 0;

function Start () {
	// Set player color
	if (player) {
		renderer.material.color = Color.green;

	// Set hostile color
	} else if (hostile) {
		renderer.material.color = Color.red;
	}
}

function Update () {
	var posV3 : Vector3 = transform.position;
	var posV2 : Vector2 = Vector2( posV3.x, posV3.z );
	var speed : float = aSpeed;
	var angle : float;

	// Influence / Acceleration
	var inf : float = 0.02;
	if (hostile) inf = 0.05;

	// Get data for surrounding agents
	// -------------------------------------------
	if (instructionUpdate <= 0 || player) {
		instructionUpdate = updateSkip*Random.value;

		// Friendly
		var fNum : int = 0;
		var fAverage : Vector2 = Vector2.zero;
		var fDistance : float = 1000;
		var fAgent : Rigidbody;

		// Enemy
		var eDistance : float = 1000;
		var eAgent : Rigidbody;

		// Get all objects touching or in range
		var colliders : Collider[] = Physics.OverlapSphere( posV3, detectionRange );

		// Check agents in proximity
		for (var crossAgent : Collider in colliders) {
			// avoid wrong references
			if (!crossAgent) continue; 
			if (!crossAgent.rigidbody) continue;
			if (rigidbody == crossAgent.rigidbody) continue;

			// Get cross brain
			var crossBrain : AgentBrain4 = crossAgent.GetComponent( AgentBrain4 ) as AgentBrain4;
			if (!crossBrain) continue;

			// Check distance
			var crossDistance : float = (posV3 - crossAgent.rigidbody.position).magnitude;

			// Is Hostile
			if (crossBrain.hostile || crossBrain.player) {
				// Closest hostile
				if (crossDistance < eDistance) {
					eDistance = crossDistance;
					eAgent = crossAgent.rigidbody;

					// Hostile too close: Suicide
					if (!hostile && crossBrain.hostile && eDistance < 2) {
						Destroy( gameObject );
						return;
					}
				}
			// Is Friendly
			} else {
				fAverage += Vector2( crossAgent.rigidbody.position.x, crossAgent.rigidbody.position.z );
				fNum++;
				// Closest friendly
				if (crossDistance < fDistance) {
					fDistance = crossDistance;
					fAgent = crossAgent.rigidbody;
				}
			}
		}

		// Behavior
		// -------------------------------------------
		var crossPosV2 : Vector2;
		fAverage.x = fAverage.x / fNum;
		fAverage.y = fAverage.y / fNum;

		// Player
		// ------------------
		if (player) {
			// Stay apart
			if (eDistance < 1.5) {
				crossPosV2 = Vector2( eAgent.position.x, eAgent.position.z );
				angle = getAngle( crossPosV2, posV2 ) +45;
				speed *= 1.3;

			// Go to mouse position
			} else {
				var ray : Ray = Camera.main.ScreenPointToRay( Input.mousePosition );
				var hit : RaycastHit;
				// Ray cast hit
				if (Physics.Raycast( ray, hit )) {
					var hitV2 : Vector2 = Vector2( hit.point.x, hit.point.z );
					angle = getAngle( hitV2, posV2 ) -90;
					speed *= 1.3;
					inf = 0.20;
				}
			}

		// Predator
		// ------------------
		} else if (hostile) {
			var curSpeed : float = Mathf.Abs(rigidbody.velocity.x + rigidbody.velocity.z);

			if ( fAgent ) {
				// Predator: Single target
				if ( fNum < 5 || fDistance < 4 ) {
					// Change color
					if (renderer.material.color != Color.blue) renderer.material.color = Color.blue;
					// Set angle
					crossPosV2 = Vector2( fAgent.position.x, fAgent.position.z );
					angle = getAngle( crossPosV2, posV2 ) -90;
					speed *= 1.4;
					inf = 0.20;

				// Predator: Multi target
				} else {
					// Change color
					if (renderer.material.color != Color.red) renderer.material.color = Color.red;
					// Set angle
					angle = getAngle( fAverage, posV2 ) -90;
					speed *= 1.3;
					inf = 0.10;
				}

			// Predator: Circulate
			} else {
				// Set angle
				angle = getAngle( Vector2.zero, posV2 ) -140; // -30;
				speed *= 1.1;
				// Change color
				if (renderer.material.color != Color.yellow) renderer.material.color = Color.yellow;
			}

		// Prey
		// ------------------
		} else {
			// Prey: Enemy nearby
			if ( eDistance < 20 ) {
				// Escape enemy
				crossPosV2 = Vector2( eAgent.position.x, eAgent.position.z );
				angle = getAngle( crossPosV2, posV2 ) +100;
				speed *= 1.2;
				inf = 0.10;

			// Prey: Friendly nearby
			} else if ( fAgent ) {
				// Distance to average position
				var fAvgDist : float = (posV3 - Vector3(fAverage.x, 0, fAverage.y)).magnitude;

				// When close, align vectors
				if (fAvgDist < 12) {
					angle = getAngle( Vector2.zero, posV2 ) -45;
					speed *= 0.8;
					
				// When far apart, go closer
				} else {
					angle = getAngle( fAverage, posV2 ) -90;
					speed *= 1.2;
				}

			// Prey: Circulate
			} else {
				// Go to zero
				angle = getAngle( Vector2.zero, posV2 ) -90;
			}
		}

		// Store instructions
		lastAngle = angle;
		lastSpeed = speed;
	} else {
		// Get last instructions
		instructionUpdate--;
		angle = lastAngle;
		speed = lastSpeed;
	}

	// Movement
	// -------------------------------------------
	var goalVec : Vector2 = Vector2.zero;

	// Goal Vector
	lastAngle = lastAngle + transform.eulerAngles.y;
	goalVec.x = Mathf.Sin( Mathf.Deg2Rad * lastAngle ) *lastSpeed;
	goalVec.y = Mathf.Cos( Mathf.Deg2Rad * lastAngle ) *-lastSpeed;

	// New Vector
	curVec.x = influence(goalVec.x, curVec.x, inf);
	curVec.y = influence(goalVec.y, curVec.y, inf);

	var grav = 0;
	if (posV3.y > 0.5) grav = -5;
	else transform.position.y = 0.5;

	// Apply Movment
	rigidbody.velocity = transform.TransformDirection(Vector3( curVec.x, grav, curVec.y ));
	
	// Fallen off the world, reset
	if (posV3.y < -50) {
		print('Resetting position');
		transform.position = Vector3(0,5,0);
	}
}


// -------------------------------------------
function influence( value1 : float, value2 : float, inf : float ) {
	var aInf : float = 1-inf;
	return (value1*inf) + (value2*aInf);
}


// -------------------------------------------
function getAngle( obj1 : Vector2, obj2 : Vector2 ) {
	var deltaX : float = obj2.x - obj1.x;
	var deltaY : float = obj2.y - obj1.y;
	var value : float = Mathf.Atan2( deltaY, deltaX );
	value = ( value * Mathf.Rad2Deg );
	return value;
}

agentSpawn.js

#pragma strict

var agentPrefab : Rigidbody;
var numAgents : int = 20;
var numPlayers : int = 0;
var numPreditors : int = 1;
private var totalNum : int = numAgents + numPreditors + numPlayers;

function Awake() {
	var clone : Rigidbody;
	var x : float;
	var z : float;
	var i : int;

	// Agents
	for(i=0; i<numAgents; i++) {
		x = Random.value*(totalNum*5) + totalNum*-2.5;
		z = Random.value*(totalNum*5) + totalNum*-2.5;
		// Clone
		clone = Instantiate( agentPrefab, Vector3( x, 15, z ), Quaternion.identity );
		clone.GetComponent( AgentBrain4 ).detectionRange = 30;
		clone.GetComponent( AgentBrain4 ).updateSkip = 0;
		clone.GetComponent( AgentBrain4 ).hostile = false;
	}

	// Preditors
	for(i=0; i<numPreditors; i++) {
		x = Random.value*(totalNum*5) + totalNum*-2.5;
		z = Random.value*(totalNum*5) + totalNum*-2.5;
		// Clone
		clone = Instantiate( agentPrefab, Vector3( x, 15, z ), Quaternion.identity );
		clone.GetComponent( AgentBrain4 ).detectionRange = 30;
		clone.GetComponent( AgentBrain4 ).updateSkip = 0;
		clone.GetComponent( AgentBrain4 ).hostile = true;
	}

	// Players
	for(i=0; i<numPlayers; i++) {
		x = Random.value*(totalNum*5) + totalNum*-2.5;
		z = Random.value*(totalNum*5) + totalNum*-2.5;
		// Clone
		clone = Instantiate( agentPrefab, Vector3( x, 15, z ), Quaternion.identity );
		clone.GetComponent( AgentBrain4 ).detectionRange = 5;
		clone.GetComponent( AgentBrain4 ).hostile = true;
		clone.GetComponent( AgentBrain4 ).player = true;
	}
}