From 8065e2645a936275c7d69c6068d80ece598d6e57 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Tomas=20Wenstr=C3=B6m?= <tomas.wenstrom@gmail.com>
Date: Mon, 8 Feb 2021 17:45:40 +0100
Subject: [PATCH] Bounce bolls off of walls in a proper angle

---
 src/common/geometry.rs |  9 +++++++--
 src/core/game.rs       | 14 +++++++++-----
 src/core/level/mod.rs  | 17 ++++++++++++++++-
 3 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/src/common/geometry.rs b/src/common/geometry.rs
index e46f23e..ebf122a 100644
--- a/src/common/geometry.rs
+++ b/src/common/geometry.rs
@@ -173,16 +173,21 @@ pub struct Radians(pub f64);
 
 impl Degrees {
     #[allow(dead_code)]
-    fn to_radians(&self) -> Radians {
+    pub fn to_radians(&self) -> Radians {
 	Radians(self.0.to_radians())
     }
 }
 
 impl Radians {
     #[allow(dead_code)]
-    fn to_degrees(&self) -> Degrees {
+    pub fn to_degrees(&self) -> Degrees {
 	Degrees(self.0.to_degrees())
     }
+
+    /// Returns the reflection of the incident when mirrored along this angle.
+    pub fn mirror(&self, incidence: Radians) -> Radians {
+	Radians((std::f64::consts::PI + self.0 * 2.0 - incidence.0) % std::f64::consts::TAU)
+    }
 }
 
 ////////// INTERSECTION ////////////////////////////////////////////////////////
diff --git a/src/core/game.rs b/src/core/game.rs
index b0d9968..39af2e1 100644
--- a/src/core/game.rs
+++ b/src/core/game.rs
@@ -275,15 +275,19 @@ impl Object for Boll {
 	    if self.bounces == 0 {
 		return Dead
 	    }
-	    self.pos = pos;
-	    self.vel *= -0.25;
-	    self.pos += self.vel;
 	    self.bounces -= 1;
+	    let mut a = wall.normal().mirror(self.vel.to_radians()); // TODO interpolera normalen mellan närliggande väggdelar? bollarna studsar väldigt "kantigt" nu
+	    self.pos = pos;
+	    self.vel = Point::from(a) * self.vel.length() * 0.35;
+	    self.pos += self.vel; // TODO det här kan få bollen att åka igenom en närliggande vägg utan att kollisionstestas, men behövs just nu för att inte kollidera med samma vägg bakifrån
+
+	    // create another boll
 	    use rand::distributions::{Distribution, Normal};
 	    let mut rng = rand::thread_rng();
-	    let a = Radians(self.vel.to_radians().0 + Normal::new(0.0, 0.75).sample(&mut rng));
+	    a.0 += Normal::new(0.0, 0.1).sample(&mut rng); // TODO slumpen kan ge en vinkel som är under tangenten. vinkel-metoder på väggen istället kanske?
+	    use rand::Rng;
 	    objects.push(Box::new(Boll {
-	    	vel: Point::from(a) * Normal::new(1.0, 0.25).sample(&mut rng) * self.vel.length(),
+	    	vel: Point::from(a) * Normal::new(1.0, 0.25).sample(&mut rng) * self.vel.length() * rng.gen_range(0.25, 1.0),
 	    	..*self
 	    }));
 	}
diff --git a/src/core/level/mod.rs b/src/core/level/mod.rs
index 84d4fad..cccd253 100644
--- a/src/core/level/mod.rs
+++ b/src/core/level/mod.rs
@@ -1,4 +1,4 @@
-use common::{Point, Dimension, Intersection, supercover_line};
+use common::{Point, Dimension, Intersection, Radians, supercover_line};
 use core::render::Renderer;
 use sprites::SpriteManager;
 use std::rc::Rc;
@@ -89,6 +89,15 @@ impl Level {
 	// walls
 	for wall in &self.walls {
 	    for e in &wall.edges {
+		let c = (e.p1 + e.p2) / 2.0;
+		let mut rad = (e.p2 - e.p1).to_radians();
+		rad.0 += std::f64::consts::FRAC_PI_2;
+
+		renderer.draw_line(
+		    <(i32, i32)>::from(c.to_i32()),
+		    <(i32, i32)>::from((c + Point::from(rad) * 10.0).to_i32()),
+		    (255, 128, 0));
+
 		renderer.draw_line(
 		    <(i32, i32)>::from(e.p1.to_i32()),
 		    <(i32, i32)>::from(e.p2.to_i32()),
@@ -238,4 +247,10 @@ impl<'a> Wall<'a> {
 	    edge,
 	}
     }
+
+    pub fn normal(&self) -> Radians {
+	let mut rad = (self.edge.p2 - self.edge.p1).to_radians();
+	rad.0 += std::f64::consts::FRAC_PI_2;
+	rad
+    }
 }
-- 
2.11.0