From 197c6df4a413f708108789d8a11f3a23537ca37f Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Sun, 12 Aug 2018 21:20:19 -0700
Subject: [PATCH] Add Plane rendering.

Add Element enum type that can hold Plane and Sphere.
---
 bheisler/src/lib.rs       | 40 ++++++++++++++++++++++++++---------
 bheisler/src/rendering.rs | 44 +++++++++++++++++++++++++++++++++++++++
 bheisler/src/scene.rs     | 10 ++++-----
 3 files changed, 79 insertions(+), 15 deletions(-)

diff --git a/bheisler/src/lib.rs b/bheisler/src/lib.rs
index 4c937ab..e32e54f 100644
--- a/bheisler/src/lib.rs
+++ b/bheisler/src/lib.rs
@@ -17,7 +17,7 @@ pub fn render(scene: &Scene) -> image::DynamicImage {
             let ray = rendering::Ray::create_prime(x, y, scene);
 
             if let Some(intersection) = scene.trace(&ray) {
-                let c = &intersection.object.color;
+                let c = &intersection.object.color();
                 image.put_pixel(x, y, image::Rgba(c.to_rgba()))
             } else {
                 image.put_pixel(x, y, black);
@@ -30,15 +30,35 @@ pub fn render(scene: &Scene) -> image::DynamicImage {
 #[test]
 fn test_can_render_scene() {
     use point::Point;
+    use rendering::Element;
+    use rendering::Plane;
     use rendering::Sphere;
     use scene::Color;
+    use vector::Vector3;
 
     let scene = Scene {
         width: 800,
         height: 600,
         fov: 90.0,
-        spheres: vec![
-            Sphere {
+        elements: vec![
+            Element::Plane(Plane {
+                origin: Point {
+                    x: 0.0,
+                    y: -2.0,
+                    z: -5.0,
+                },
+                normal: Vector3 {
+                    x: 0.0,
+                    y: -1.0,
+                    z: 0.0,
+                },
+                color: Color {
+                    red: 0.2,
+                    green: 0.2,
+                    blue: 0.3,
+                },
+            }),
+            Element::Sphere(Sphere {
                 center: Point {
                     x: 2.0,
                     y: 1.0,
@@ -50,8 +70,8 @@ fn test_can_render_scene() {
                     green: 0.2,
                     blue: 0.2,
                 },
-            },
-            Sphere {
+            }),
+            Element::Sphere(Sphere {
                 center: Point {
                     x: 0.0,
                     y: 0.0,
@@ -63,8 +83,8 @@ fn test_can_render_scene() {
                     green: 1.0,
                     blue: 0.2,
                 },
-            },
-            Sphere {
+            }),
+            Element::Sphere(Sphere {
                 center: Point {
                     x: -3.0,
                     y: 1.0,
@@ -76,8 +96,8 @@ fn test_can_render_scene() {
                     green: 0.2,
                     blue: 1.0,
                 },
-            },
-            Sphere {
+            }),
+            Element::Sphere(Sphere {
                 center: Point {
                     x: 2.0,
                     y: 1.0,
@@ -89,7 +109,7 @@ fn test_can_render_scene() {
                     green: 1.0,
                     blue: 1.0,
                 },
-            },
+            }),
         ],
     };
 
diff --git a/bheisler/src/rendering.rs b/bheisler/src/rendering.rs
index 29460a6..8c075e9 100644
--- a/bheisler/src/rendering.rs
+++ b/bheisler/src/rendering.rs
@@ -39,6 +39,50 @@ impl Intersectable for Sphere {
     }
 }
 
+pub struct Plane {
+    pub origin: Point,
+    pub normal: Vector3,
+    pub color: Color,
+}
+
+impl Intersectable for Plane {
+    fn intersect(&self, ray: &Ray) -> Option<f32> {
+        let normal = &self.normal;
+        let denom = normal.dot(&ray.direction);
+        if denom > 1e-6 {
+            let v: Vector3 = (self.origin - ray.origin).into();
+            let distance = v.dot(&normal) / denom;
+            if distance >= 0.0 {
+                return Some(distance);
+            }
+        }
+        None
+    }
+}
+
+pub enum Element {
+    Sphere(Sphere),
+    Plane(Plane),
+}
+
+impl Element {
+    pub fn color(&self) -> &Color {
+        match *self {
+            Element::Sphere(ref s) => &s.color,
+            Element::Plane(ref p) => &p.color,
+        }
+    }
+}
+
+impl Intersectable for Element {
+    fn intersect(&self, ray: &Ray) -> Option<f32> {
+        match *self {
+            Element::Sphere(ref s) => s.intersect(ray),
+            Element::Plane(ref p) => p.intersect(ray),
+        }
+    }
+}
+
 pub struct Ray {
     pub origin: Point,
     pub direction: Vector3,
diff --git a/bheisler/src/scene.rs b/bheisler/src/scene.rs
index 62c98c1..3d3ce06 100644
--- a/bheisler/src/scene.rs
+++ b/bheisler/src/scene.rs
@@ -1,14 +1,14 @@
+use rendering::Element;
 use rendering::Intersectable;
 use rendering::Ray;
-use rendering::Sphere;
 
 pub struct Intersection<'a> {
     pub distance: f32,
-    pub object: &'a Sphere,
+    pub object: &'a Element,
 }
 
 impl<'a> Intersection<'a> {
-    pub fn new(distance: f32, object: &Sphere) -> Intersection {
+    pub fn new(distance: f32, object: &Element) -> Intersection {
         Intersection { distance, object }
     }
 }
@@ -35,12 +35,12 @@ pub struct Scene {
     pub width: u32,
     pub height: u32,
     pub fov: f32,
-    pub spheres: Vec<Sphere>,
+    pub elements: Vec<Element>,
 }
 
 impl Scene {
     pub fn trace(&self, ray: &Ray) -> Option<Intersection> {
-        self.spheres
+        self.elements
             .iter()
             .filter_map(|s| s.intersect(ray).map(|d| Intersection::new(d, s)))
             .min_by(|i1, i2| i1.distance.partial_cmp(&i2.distance).unwrap())