From 0c5c6381fceaac3cfb89f0df1df0ad5be406623b Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Sat, 8 Sep 2018 17:17:29 -0700
Subject: [PATCH] Start of surface normal support.

---
 bheisler/src/lib.rs       | 17 +++++++++++++++++
 bheisler/src/point.rs     | 15 +++++++++++++++
 bheisler/src/rendering.rs | 22 +++++++++++++++++++++
 bheisler/src/scene.rs     |  8 ++++++++
 bheisler/src/vector.rs    | 40 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 102 insertions(+)

diff --git a/bheisler/src/lib.rs b/bheisler/src/lib.rs
index 7132b49..807c24d 100644
--- a/bheisler/src/lib.rs
+++ b/bheisler/src/lib.rs
@@ -17,6 +17,9 @@ pub fn render(scene: &Scene) -> image::DynamicImage {
             let ray = rendering::Ray::create_prime(x, y, scene);
 
             if let Some(intersection) = scene.trace(&ray) {
+                let hit_point = ray.origin + (&ray.direction * intersection.distance);
+                let surface_normal = intersection.object.surface_normal(&hit_point);
+                let direction_to_light = -scene.light.direction;
                 let c = &intersection.object.color();
                 image.put_pixel(x, y, image::Rgba(c.to_rgba()))
             } else {
@@ -34,6 +37,7 @@ fn test_can_render_scene() {
     use rendering::Plane;
     use rendering::Sphere;
     use scene::Color;
+    use scene::Light;
     use vector::Vector3;
 
     let scene = Scene {
@@ -128,6 +132,19 @@ fn test_can_render_scene() {
                 },
             }),
         ],
+        light: Light {
+            direction: Vector3 {
+                x: 0.0,
+                y: 0.0,
+                z: -1.0,
+            },
+            color: Color {
+                red: 1.0,
+                green: 1.0,
+                blue: 1.0,
+            },
+            intensity: 0.0,
+        },
     };
 
     let img: image::DynamicImage = render(&scene);
diff --git a/bheisler/src/point.rs b/bheisler/src/point.rs
index 78a04f7..309a07f 100644
--- a/bheisler/src/point.rs
+++ b/bheisler/src/point.rs
@@ -1,5 +1,8 @@
+use std::ops::Add;
 use std::ops::Sub;
 
+use vector::Vector3;
+
 #[derive(Clone, Copy)]
 pub struct Point {
     pub x: f32,
@@ -17,6 +20,18 @@ impl Point {
     }
 }
 
+impl Add<Vector3> for Point {
+    type Output = Point;
+
+    fn add(self, other: Vector3) -> Point {
+        Point {
+            x: self.x + other.x,
+            y: self.y + other.y,
+            z: self.z + other.z,
+        }
+    }
+}
+
 impl Sub for Point {
     type Output = Point;
 
diff --git a/bheisler/src/rendering.rs b/bheisler/src/rendering.rs
index 8c075e9..ffc6ac3 100644
--- a/bheisler/src/rendering.rs
+++ b/bheisler/src/rendering.rs
@@ -5,6 +5,7 @@ use vector::Vector3;
 
 pub trait Intersectable {
     fn intersect(&self, ray: &Ray) -> Option<f32>;
+    fn surface_normal(&self, hit_point: &Point) -> Vector3;
 }
 
 pub struct Sphere {
@@ -37,6 +38,10 @@ impl Intersectable for Sphere {
         let distance = if t0 < t1 { t0 } else { t1 };
         Some(distance)
     }
+
+    fn surface_normal(&self, hit_point: &Point) -> Vector3 {
+        Vector3::from(*hit_point - self.center).normalize()
+    }
 }
 
 pub struct Plane {
@@ -58,6 +63,10 @@ impl Intersectable for Plane {
         }
         None
     }
+
+    fn surface_normal(&self, _: &Point) -> Vector3 {
+        -self.normal
+    }
 }
 
 pub enum Element {
@@ -72,6 +81,12 @@ impl Element {
             Element::Plane(ref p) => &p.color,
         }
     }
+    pub fn surface_normal(&self, hit_point: &Point) -> Vector3 {
+        match *self {
+            Element::Sphere(ref s) => s.surface_normal(hit_point),
+            Element::Plane(ref p) => p.surface_normal(hit_point),
+        }
+    }
 }
 
 impl Intersectable for Element {
@@ -81,6 +96,13 @@ impl Intersectable for Element {
             Element::Plane(ref p) => p.intersect(ray),
         }
     }
+
+    fn surface_normal(&self, hit_point: &Point) -> Vector3 {
+        match *self {
+            Element::Sphere(ref s) => s.surface_normal(hit_point),
+            Element::Plane(ref p) => p.surface_normal(hit_point),
+        }
+    }
 }
 
 pub struct Ray {
diff --git a/bheisler/src/scene.rs b/bheisler/src/scene.rs
index 3d3ce06..4dca3f7 100644
--- a/bheisler/src/scene.rs
+++ b/bheisler/src/scene.rs
@@ -1,6 +1,7 @@
 use rendering::Element;
 use rendering::Intersectable;
 use rendering::Ray;
+use vector::Vector3;
 
 pub struct Intersection<'a> {
     pub distance: f32,
@@ -31,11 +32,18 @@ impl Color {
     }
 }
 
+pub struct Light {
+    pub direction: Vector3,
+    pub color: Color,
+    pub intensity: f32,
+}
+
 pub struct Scene {
     pub width: u32,
     pub height: u32,
     pub fov: f32,
     pub elements: Vec<Element>,
+    pub light: Light,
 }
 
 impl Scene {
diff --git a/bheisler/src/vector.rs b/bheisler/src/vector.rs
index b029765..0d110d8 100644
--- a/bheisler/src/vector.rs
+++ b/bheisler/src/vector.rs
@@ -1,6 +1,10 @@
 use point::Point;
+use std::ops::Add;
 use std::ops::Div;
+use std::ops::Mul;
+use std::ops::Neg;
 
+#[derive(Clone, Copy)]
 pub struct Vector3 {
     pub x: f32,
     pub y: f32,
@@ -37,6 +41,42 @@ impl<'a> Div<f32> for &'a Vector3 {
     }
 }
 
+impl<'a> Mul<f32> for &'a Vector3 {
+    type Output = Vector3;
+
+    fn mul(self, rhs: f32) -> Vector3 {
+        Vector3 {
+            x: self.x * rhs,
+            y: self.y * rhs,
+            z: self.z * rhs,
+        }
+    }
+}
+
+impl Add for Vector3 {
+    type Output = Vector3;
+
+    fn add(self, rhs: Vector3) -> Vector3 {
+        Vector3 {
+            x: rhs.x + self.x,
+            y: rhs.y + self.y,
+            z: rhs.z + self.z,
+        }
+    }
+}
+
+impl Neg for Vector3 {
+    type Output = Vector3;
+
+    fn neg(self) -> Vector3 {
+        Vector3 {
+            x: -self.x,
+            y: -self.y,
+            z: -self.z,
+        }
+    }
+}
+
 impl From<Point> for Vector3 {
     fn from(p: Point) -> Self {
         Vector3 {