From 0bcc2c31352a47e12a776c221730ba0249b38bad Mon Sep 17 00:00:00 2001
From: Allanis <allanis@saracraft.net>
Date: Wed, 7 Aug 2013 12:14:47 +0100
Subject: [PATCH] [Add] vect_reflect() - Mirror a vector off another.

---
 src/physics.c | 11 +++++++++++
 src/physics.h |  1 +
 2 files changed, 12 insertions(+)

diff --git a/src/physics.c b/src/physics.c
index 8cd3035..99dc5ec 100644
--- a/src/physics.c
+++ b/src/physics.c
@@ -74,6 +74,17 @@ void vect_cadd(Vec2* v, const double x, const double y) {
   v->angle = ANGLE(v->x, v->y);
 }
 
+/* Mirrors a vector off another, stores results in vector. */
+void vect_reflect(Vec2* r, Vec2* v, Vec2* n) {
+  double dot;
+
+  dot       = (v->x*n->x) + (v->y*n->y);
+  r->x      = v->x - ((2. * dot) * n->x);
+  r->y      = v->y - ((2. * dot) * n->y);
+  r->mod    = MOD(r->x, r->y);
+  r->angle  = MOD(r->x, r->y);
+
+}
 
 /* ================ */
 /* SOLID! */
diff --git a/src/physics.h b/src/physics.h
index ebf7caf..b00056d 100644
--- a/src/physics.h
+++ b/src/physics.h
@@ -33,6 +33,7 @@ void vectcpy(Vec2* dest, const Vec2* src);
 void vectnull(Vec2* v);
 double vect_angle(const Vec2* ref, const Vec2* v);
 void vect_cadd(Vec2* v, const double x, const double y);
+void vect_reflect(Vec2* r, Vec2* v, Vec2* n);
 
 /* Describe any solid in 2D space. */
 typedef struct Solid_ {