From 00357f94900f05f304f83b96b168d433e3fb3a69 Mon Sep 17 00:00:00 2001
From: gbrochar <gaetanbrochard@protonmail.com>
Date: Thu, 10 Dec 2020 21:38:07 +0100
Subject: [PATCH] sphere intersection

---
 Cargo.toml    |  4 +++-
 src/lib.rs    |  7 +++++++
 src/object.rs |  7 +++++++
 src/ray.rs    |  6 ++++++
 src/sphere.rs | 37 +++++++++++++++++++++++++++++++++++++
 5 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 src/lib.rs
 create mode 100644 src/object.rs
 create mode 100644 src/ray.rs
 create mode 100644 src/sphere.rs

diff --git a/Cargo.toml b/Cargo.toml
index ae2bd15..a9ebd40 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,4 +7,6 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-mat4 = "0.2.1"
\ No newline at end of file
+mat4 = "0.2.1"
+vec3 = "0.2.1"
+arrayvec = "0.5.2"
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..4a3e8c1
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,7 @@
+mod object;
+mod ray;
+mod sphere;
+
+pub use self::object::*;
+pub use self::ray::*;
+pub use self::sphere::*;
diff --git a/src/object.rs b/src/object.rs
new file mode 100644
index 0000000..5dcd436
--- /dev/null
+++ b/src/object.rs
@@ -0,0 +1,7 @@
+use super::Ray;
+use arrayvec::ArrayVec;
+
+pub trait Object {
+    fn get_intersection(&self, ray: Ray) -> Option<f64>;
+    fn get_normal(&self) -> ArrayVec<[f64; 3]>;
+}
diff --git a/src/ray.rs b/src/ray.rs
new file mode 100644
index 0000000..3283fa9
--- /dev/null
+++ b/src/ray.rs
@@ -0,0 +1,6 @@
+use arrayvec::ArrayVec;
+
+pub struct Ray {
+    pub origin: ArrayVec<[f64; 3]>,
+    pub direction: ArrayVec<[f64; 3]>,
+}
diff --git a/src/sphere.rs b/src/sphere.rs
new file mode 100644
index 0000000..bb04767
--- /dev/null
+++ b/src/sphere.rs
@@ -0,0 +1,37 @@
+use super::Object;
+use super::Ray;
+use arrayvec::ArrayVec;
+
+struct Sphere {}
+
+fn return_min(root1: f64, root2: f64) -> Option<f64> {
+    if root1 < root2 && root1 > 0. {
+        Some(root1)
+    } else if root2 < root1 && root2 > 0. {
+        Some(root2)
+    } else {
+        None
+    }
+}
+
+impl Object for Sphere {
+    fn get_intersection(&self, ray: Ray) -> Option<f64> {
+        let a = ray.direction[0].powi(2) + ray.direction[1].powi(2) + ray.direction[2].powi(2);
+        let b = (2. * ray.origin[0] * ray.direction[0])
+            + (2. * ray.origin[1] * ray.direction[1])
+            + (2. * ray.origin[2] * ray.direction[2]);
+        let c = ray.origin[0].powi(2) + ray.origin[1].powi(2) + ray.origin[2].powi(2) - 1.;
+        let delta = b * b - 4. * a * c;
+
+        if delta > 0. {
+            let root1 = ((-1. * b - delta.sqrt()) / (a + a)) - 0.00001;
+            let root2 = ((-1. * b + delta.sqrt()) / (a + a)) - 0.00001;
+            return_min(root1, root2)
+        } else {
+            None
+        }
+    }
+    fn get_normal(&self) -> ArrayVec<[f64; 3]> {
+        ArrayVec::<[f64; 3]>::new()
+    }
+}