From 02455892dac1d52914e5702fd8e895d5cee1f083 Mon Sep 17 00:00:00 2001
From: FBeans <phil@pgburton.com>
Date: Sat, 21 May 2022 19:07:32 +0100
Subject: Add world, boid and all collision detection

---
 src/Collision/Collision.php | 141 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 src/Collision/Collision.php

(limited to 'src/Collision')

diff --git a/src/Collision/Collision.php b/src/Collision/Collision.php
new file mode 100644
index 0000000..a896777
--- /dev/null
+++ b/src/Collision/Collision.php
@@ -0,0 +1,141 @@
+<?php
+
+namespace App\Collision;
+
+
+class Collision
+{
+    protected const BUFFER = 0.1;
+
+    public static function circleRectangle(int $c_radius, int $c_x, int $c_y, int $r_w, int $r_h, int $r_x, int $r_y): bool
+    {
+        $test_x = $c_x;
+        $test_y = $c_y;
+
+        if ($c_x < $r_x) {
+            $test_x = $r_x;
+        } elseif ($c_x > $r_x + $r_w) {
+            $test_x = $r_x + $r_w;
+        }
+
+        if ($c_y < $r_y) {
+            $test_y = $r_y;
+        } elseif ($c_y > $r_y + $r_h) {
+            $test_y = $r_y + $r_h;
+        }
+
+        $dist_x = $c_x - $test_x;
+        $dist_y = $c_y - $test_y;
+
+        $distance = sqrt( ($dist_x * $dist_y) + ($dist_y * $dist_y) );
+
+        if ($distance <= $c_radius) {
+            return true;
+        }
+
+        return false;
+    }
+
+    public static function circleWorld(int $c_radius, int $c_x, int $c_y, int $w_w, int $w_h, int $w_x, int $w_y): bool
+    {
+        if (static::circleOutsideRectangle($c_radius, $c_x, $c_y, $w_w, $w_h, $w_x, $w_y)) {
+            return true;
+        }
+
+        if (static::lineCircle($w_x, $w_x, $w_y, $w_y+$w_h, $c_x, $c_y, $c_radius)) {
+            return true;
+        }
+
+        if (static::lineCircle($w_x+$w_w, $w_x+$w_w, $w_y, $w_y+$w_h, $c_x, $c_y, $c_radius)) {
+            return true;
+        }
+
+        if (static::lineCircle($w_x, $w_x+$w_w, $w_y, $w_y, $c_x, $c_y, $c_radius)) {
+            return true;
+        }
+
+        if (static::lineCircle($w_x, $w_x+$w_w, $w_y+$w_h, $w_y+$w_h, $c_x, $c_y, $c_radius)) {
+            return true;
+        }
+
+        return false;
+
+    }
+
+    public static function circleOutsideRectangle(int $c_radius, int $c_x, int $c_y, int $w_w, int $w_h, int $w_x, int $w_y)
+    {
+        if ($c_x + $c_radius < $w_x) {
+            return true;
+        }
+
+        if ($c_x - $c_radius > $w_x + $w_w) {
+            return true;
+        }
+
+        if ($c_y + $c_radius < $w_y) {
+            return true;
+        }
+
+        if ($c_y - $c_radius > $w_y + $w_h) {
+            return true;
+        }
+
+        return false;
+    }
+
+    public static function lineCircle(int $x_1, int $x_2, int $y_1, int $y_2, int $c_x, int $c_y, int $c_radius): bool
+    {
+        if (static::pointCircle($x_1, $y_1, $c_x, $c_y, $c_radius)) {
+            return true;
+        }
+
+        if (static::pointCircle($x_2, $y_2, $c_x, $c_y, $c_radius)) {
+            return true;
+        }
+
+        $length = static::distance($x_1, $x_2, $y_1, $y_2);
+
+        $dot = ((($c_x - $x_1) * ($x_2 - $x_1)) + (($c_y - $y_1) * ($y_2 - $y_1))) / ($length * $length);
+        $dot = number_format($dot, 4);
+
+        $closest_x = $x_1 + ($dot * ($x_2 - $x_1));
+        $closest_y = $y_1 +_($dot * ($y_2 - $y_1));
+
+        if (!static::linePoint($x_1, $x_2, $y_1, $y_2, $closest_x, $closest_y)) {
+            return false;
+        }
+
+        $distance = static::distance($closest_x, $c_x, $closest_y, $c_y);
+
+        return $distance <= $c_radius;
+    }
+
+    public static function linePoint(int $x_1, int $x_2, int $y_1, int $y_2, int $p_x, int $p_y)
+    {
+        $d_1 = static::distance($p_x, $x_1, $p_y, $y_1);
+        $d_2 = static::distance($p_x, $x_2, $p_y, $y_2);
+
+        $length = static::distance($x_1, $x_2, $y_1, $y_2);
+
+        return $d_1 + $d_2 >= $length - static::BUFFER
+            && $d_1 + $d_2 <= $length + static::BUFFER;
+    }
+
+    public static function pointCircle(int $p_x, int $p_y, int $c_x, int $c_y, int $c_radius): bool
+    {
+        $distance = static::distance($p_x, $c_x, $p_y, $c_y);
+
+        return $distance <= $c_radius;
+    }
+
+    public static function distance(int $x_1, int $x_2, int $y_1, int $y_2): float
+    {
+        $d_x = $x_1 - $x_2;
+        $d_y = $y_1 - $y_2;
+
+        return number_format(
+            sqrt( ($d_x * $d_x) + ($d_y * $d_y)),
+            2
+        );
+    }
+}
-- 
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