# Ants

We spent some time in Nature of Code learning about Autonomous Steering Behaviors. This is a fancy umbrella term for simulations of group and individual movements “in the wild.” This can describe phenomena like the flocking of birds, or the way a crowd moves when shuffling into a doorway.

I combined the Wander and Separate examples to make a colony of ants. The overall movement feels almost right, but for some reason I could not get the ants’ bodies to angle in the direction of their movement. This is problematic because it makes them move backward as well as forward. This may have been caused by the way I constructed the ants in Processing–I started from the middle and worked my way out, working from the front or the back.

Main sketch code:

```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 ArrayList <Vehicle> ants;   void setup() { size(600, 600); smooth();   ants = new ArrayList<Vehicle>(); for (int i = 0; i < 50; i++) { ants.add(new Vehicle(random(width),random(height))); } }   void draw() { background(58, 188, 15); fill(6, 72, 32); noStroke(); randomSeed(15); for(int j=0; j<300; j++) { rect(random(width), random(height), 2, 15); } fill(137, 252, 8); for(int j=0; j<300; j++) { rect(random(width), random(height), 2, 15); }   for (Vehicle v : ants) { // Path following and separation are worked on in this function v.separate(ants); // Call the generic run method (update, borders, display, etc.) v.update(); v.borders(); v.display(); v.wander(); } }```

Vehicle (ant) class code:

```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144   class Vehicle {   // All the usual stuff PVector location; PVector velocity; PVector acceleration; float r; float maxforce; // Maximum steering force float maxspeed; // Maximum speed float wandertheta;   // Constructor initialize all values Vehicle(float x, float y) { location = new PVector(x, y); r = 12; maxspeed = 3; maxforce = 0.2; acceleration = new PVector(0, 0); velocity = new PVector(0, 0); wandertheta = 0; }   void applyForce(PVector force) { // We could add mass here if we want A = F / M acceleration.add(force); }   // Separation // Method checks for nearby vehicles and steers away void separate (ArrayList<Vehicle> vehicles) { float desiredseparation = r*2; PVector sum = new PVector(); int count = 0; // For every boid in the system, check if it's too close for (Vehicle other : vehicles) { float d = PVector.dist(location, other.location); // If the distance is greater than 0 and less than an arbitrary amount (0 when you are yourself) if ((d > 0) && (d < desiredseparation)) { // Calculate vector pointing away from neighbor PVector diff = PVector.sub(location, other.location); diff.normalize(); diff.div(d); // Weight by distance sum.add(diff); count++; // Keep track of how many } } // Average -- divide by how many if (count > 0) { sum.div(count); // Our desired vector is the average scaled to maximum speed sum.normalize(); sum.mult(maxspeed); // Implement Reynolds: Steering = Desired - Velocity PVector steer = PVector.sub(sum, velocity); steer.limit(maxforce); applyForce(steer); } }   void wander() { float wanderR = 25; // Radius for our "wander circle" float wanderD = 40; // Distance for our "wander circle" float change = 0.5; wandertheta += random(-change,change); // Randomly change wander theta   // Now we have to calculate the new location to steer towards on the wander circle PVector circleloc = velocity.get(); // Start with velocity circleloc.normalize(); // Normalize to get heading circleloc.mult(wanderD); // Multiply by distance circleloc.add(location); // Make it relative to boid's location   float h = velocity.heading2D(); // We need to know the heading to offset wandertheta   PVector circleOffSet = new PVector(wanderR*cos(wandertheta+h),wanderR*sin(wandertheta+h)); PVector target = PVector.add(circleloc,circleOffSet); seek(target);   // Render wandering circle, etc. //if (debug) drawWanderStuff(location,circleloc,target,wanderR); } // A method that calculates and applies a steering force towards a target // STEER = DESIRED MINUS VELOCITY void seek(PVector target) { PVector desired = PVector.sub(target,location); // A vector pointing from the location to the target   // Normalize desired and scale to maximum speed desired.normalize(); desired.mult(maxspeed); // Steering = Desired minus Velocity PVector steer = PVector.sub(desired,velocity); steer.limit(maxforce); // Limit to maximum steering force   applyForce(steer); }     // Method to update location void update() { // Update velocity velocity.add(acceleration); // Limit speed velocity.limit(maxspeed); location.add(velocity); // Reset accelertion to 0 each cycle acceleration.mult(0); }   void display() { fill(175); pushMatrix(); translate(location.x, location.y); smooth(); noStroke(); fill(82, 40, 36); ellipse(location.x+20, location.y, 11, 11.5); //body ellipse(location.x+10, location.y, 10, 8); ellipse(location.x, location.y, 12, 8); ellipse(location.x-13, location.y, 20, 13); stroke(82, 40, 36); strokeWeight(1); line(location.x+12, location.y, location.x+8, location.y-12); //front legs line(location.x+12, location.y, location.x+8, location.y+12); line(location.x+8, location.y-12, location.x+20, location.y-8); line(location.x+8, location.y+12, location.x+20, location.y+8); line(location.x-4, location.y, location.x-8, location.y-12); //bottom legs line(location.x-4, location.y, location.x-8, location.y+12); line(location.x-8, location.y+12, location.x-20, location.y+17); line(location.x-8, location.y-12, location.x-20, location.y-17); line(location.x+2, location.y, location.x+6, location.y-12); //middle legs line(location.x+2, location.y, location.x+6, location.y+12); line(location.x+6, location.y-12, location.x-6, location.y-16); line(location.x+6, location.y+12, location.x-6, location.y+16); popMatrix(); }   // Wraparound void borders() { if (location.x < -r) location.x = width+r; if (location.y < -r) location.y = height+r; if (location.x > width+r) location.x = -r; if (location.y > height+r) location.y = -r; } }```