From a44e609b27642afc77495293d975f2ea0bbf6f3e Mon Sep 17 00:00:00 2001
From: Fbenas <philbeansburton@gmail.com>
Date: Tue, 13 Oct 2020 21:58:58 +0100
Subject: Add maths function to detect two intersection circles

---
 resources/js/boid.js | 138 ++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 108 insertions(+), 30 deletions(-)

(limited to 'resources/js/boid.js')

diff --git a/resources/js/boid.js b/resources/js/boid.js
index 2ae692d..85793ff 100644
--- a/resources/js/boid.js
+++ b/resources/js/boid.js
@@ -36,11 +36,23 @@ class Boid {
 
         let rayInteval = 2;
         let noOfSteps = this.fieldOfView / rayInteval;
+        let is_clockwise = Math.random() >= 0.5;
+
         for (let i = 0; i < noOfSteps / 2; i++) {
-            if (i != 0) {
+            if (i == 0) {
+                rays.push(rayInteval * i);
+                continue;
+            }
+
+            if (is_clockwise) {
                 rays.push(rayInteval * -i);
             }
+
             rays.push(rayInteval * i);
+
+            if (!is_clockwise) {
+                rays.push(rayInteval * -i);
+            }
         }
 
         return rays;
@@ -57,10 +69,12 @@ class Boid {
 
             let rayAngle = tweakAngle + this.direction + rays[i];
 
-            if (i == 0 && this.detectBoid(rayAngle, boids)) {
+            // Check against all other boids
+            if (i == 0 && this.detectBoids(rayAngle, boids)) {
                 continue;
             }
 
+            // Check against scene boundaries
             if (this.detectBox(this.scene_width, this.scene_height, rayAngle)) {
                 continue;
             }
@@ -71,34 +85,9 @@ class Boid {
         console.log('cannot find suitable ray');
     }
 
-    detectBoid(direction, boids) {
+    detectBoids(direction, boids) {
         for (let i = 0; i < boids.length; i++) {
-            // rule out ourselves
-            if (this.id == boids[i].id) {
-                continue;
-            }
-
-            let thisFututrePosition = this.findPoint(this.x, this.y, this.boidBuffer, direction);
-            let thisPath = {
-                x1: this.x,
-                y1: this.y,
-                x2: thisFututrePosition.x,
-                y2: thisFututrePosition.y
-            };
-
-            let boidFuturePosition = this.findPoint(boids[i].x, boids[i].y, boids[i].boidBuffer, boids[i].direction);
-            let boidPath = {
-                x1: boids[i].x,
-                y1: boids[i].y,
-                x2: boidFuturePosition.x,
-                y2: boidFuturePosition.y
-            };
-
-            let thisIntersectsBoid = this.pathsIntersect(
-                thisPath.x1, thisPath.y1, thisPath.x2, thisPath.y2, boidPath.x1, boidPath.y1, boidPath.x2, boidPath.y2
-            );
-
-            if (thisIntersectsBoid) {
+            if (this.detectBoid(direction, boids[i])) {
                 return true;
             }
         }
@@ -106,6 +95,95 @@ class Boid {
         return false;
     }
 
+    detectBoid(direction, boid) {
+        // rule out ourselves
+        if (this.id == boid.id) {
+            return false;
+        }
+
+        // let cross = this.doPathsCross(direction, boid);
+        //
+        // if (cross) {
+        //     console.log('paths cross detected');
+        // }
+
+        let intersect = this.boidsIntersect(boid);
+
+        if (intersect) {
+            console.log('boids intersect detected');
+        }
+    }
+
+    boidsIntersect(boid) {
+        this.twoCirclesIntersect(this.radius, boid.radius, this.x, boid.x, this.y, boid.y);
+    }
+
+    twoCirclesIntersect(r1, r2, x1, x2, y1, y2) {
+        // from https://planetcalc.com/8098/ (bottom of page)
+        // https://mathworld.wolfram.com/Circle-CircleIntersection.html
+        // d is the abs distance between the two circles center
+        let d = this.distanceBetweenPoints(x1, x2, y1, y2);
+
+        // a is distance to our x3 point ( I think )
+        let a = (Math.pow(r1, 2) - Math.pow(r2, 2) + Math.pow(d, 2)) / (2 * d);
+
+        // h is some other segment of some other circle ( I dont really know )
+        let h = Math.sqrt(Math.pow(r1, 2) - Math.pow(a, 2));
+
+        // x3 and y3 represent the point between the two circle midpoints, perpindicular to which will be our intersects
+        // ( maybe )
+        let x3 = x1 + ((a / d) * (x2 - x1));
+        let y3 = y1 + ((a / d) * (y2 - y1));
+
+        // x4 and y4 are one of the intersect points
+        let x4 = x3 + ((h / d) * (y2 - y1));
+        let y4 = y3 - ((h / d) * (x2 - x1));
+
+        if (!x4 || !y4) {
+            return false;
+        }
+        console.log('intersecting circles');
+        return {
+            x: x4,
+            y: y4
+        };
+    }
+
+    distanceBetweenPoints(x1, x2, y1, y2) {
+        let dx = Math.abs(x1 - x2);
+        let dy = Math.abs(y1 - y2);
+
+        return Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
+    }
+
+    doPathsCross(direction, boid) {
+        let thisFututrePosition = this.findPoint(this.x, this.y, this.boidBuffer, direction);
+        let thisPath = {
+            x1: this.x,
+            y1: this.y,
+            x2: thisFututrePosition.x,
+            y2: thisFututrePosition.y
+        };
+
+        let boidFuturePosition = this.findPoint(boid.x, boid.y, boid.boidBuffer, boid.direction);
+        let boidPath = {
+            x1: boid.x,
+            y1: boid.y,
+            x2: boidFuturePosition.x,
+            y2: boidFuturePosition.y
+        };
+
+        let thisIntersectsBoid = this.pathsIntersect(
+            thisPath.x1, thisPath.y1, thisPath.x2, thisPath.y2, boidPath.x1, boidPath.y1, boidPath.x2, boidPath.y2
+        );
+
+        if (thisIntersectsBoid) {
+            return true;
+        }
+
+        return false;
+    }
+
     pathsIntersect(x1, y1, x2, y2, x3, y3, x4, y4) {
         // Check if none of the lines are of length 0
         if ((x1 === x2 && y1 === y2) || (x3 === x4 && y3 === y4)) {
@@ -165,7 +243,7 @@ class Boid {
 
     draw(context) {
         this.drawBoid(context);
-        this.drawRay(context, this.x, this.y, this.rayLength, this.direction);
+        // this.drawRay(context, this.x, this.y, this.rayLength, this.direction);
     }
 
     drawBoid(context) {
-- 
cgit v1.2.3