From 7a8fe60eb17d66771b153280b76546bcf46a9c7e Mon Sep 17 00:00:00 2001
From: Justin Worthe <justin@worthe-it.co.za>
Date: Tue, 1 May 2018 11:35:17 +0200
Subject: Vector times scalar and unit vectors

---
 src/entities/bug.rs | 24 +++++++++++-------------
 src/geometry.rs     | 26 ++++++++++++++++++++++++++
 src/main.rs         |  3 +--
 3 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/src/entities/bug.rs b/src/entities/bug.rs
index 913253c..f64669d 100644
--- a/src/entities/bug.rs
+++ b/src/entities/bug.rs
@@ -5,31 +5,29 @@ use hitbox::*;
 pub struct Bug {
     pub pos: Vec2d,
     pub rotation: f64,
+    pub velocity: Vec2d,
     pub alive: bool
 }
 
 const SPEED: f64 = 175.;
 
 impl Bug {
-    pub fn new(x: f64, y: f64, facing: f64) -> Bug {
+    pub fn new(x: f64, y: f64) -> Bug {
+        let pos = Vec2d {
+            x: x,
+            y: y
+        };
+        let pos_unit = pos.unit();
         Bug {
-            pos: Vec2d {
-                x: x,
-                y: y
-            },
-            rotation: facing,
+            pos: pos,
+            rotation: (-pos).angle(),
+            velocity: -pos_unit * SPEED,
             alive: true
         }
     }
 
     pub fn advance(&mut self, seconds: f64) {
-        self.rotation = (-self.pos).angle();
-        let distance = SPEED*seconds;
-        let delta_pos = Vec2d {
-            x: distance * self.rotation.cos(),
-            y: distance * self.rotation.sin()
-        };
-        self.pos = self.pos + delta_pos;
+        self.pos = self.pos + self.velocity * seconds;
     }
 }
 
diff --git a/src/geometry.rs b/src/geometry.rs
index c49fe2a..f84a973 100644
--- a/src/geometry.rs
+++ b/src/geometry.rs
@@ -14,9 +14,24 @@ impl Vec2d {
         ((other.x-self.x).powi(2) + (other.y-self.y).powi(2))
     }
 
+    pub fn magnitude(&self) -> f64 {
+        self.magnitude_squared().sqrt()
+    }
+    pub fn magnitude_squared(&self) -> f64 {
+        self.x.powi(2) + self.y.powi(2)
+    }
+
     pub fn angle(&self) -> f64 {
         self.y.atan2(self.x)
     }
+
+    pub fn unit(&self) -> Vec2d {
+        let mag = self.magnitude();
+        Vec2d {
+            x: self.x / mag,
+            y: self.y / mag
+        }
+    }
 }
 
 impl Add for Vec2d {
@@ -51,3 +66,14 @@ impl Neg for Vec2d {
         }
     }
 }
+
+impl Mul<f64> for Vec2d {
+    type Output = Vec2d;
+
+    fn mul(self, rhs: f64) -> Self {
+        Vec2d {
+            x: self.x * rhs,
+            y: self.y * rhs
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 98dd39f..857e744 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -66,8 +66,7 @@ impl App<AssetId> for BugBasherGame {
                 let angle = angle_dist.ind_sample(&mut self.rng);
                 self.bugs.push(Bug::new(
                     angle.cos()*1000.,
-                    angle.sin()*1000.,
-                    angle + PI
+                    angle.sin()*1000.
                 ));
                 
             }
-- 
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