From 5ef0ca76e606c7b26927bdd7191fcf97b11eb8a4 Mon Sep 17 00:00:00 2001
From: mitchellhansen <mitchellhansen0@gmail.com>
Date: Tue, 1 Dec 2020 23:51:14 -0800
Subject: [PATCH] blinn function

---
 src/main.rs | 99 ++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 90 insertions(+), 9 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 7501f36..160fd99 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,7 @@
 extern crate rand;
 
 use std::cmp::max;
+use std::cmp::min;
 use std::f32::consts::PI;
 use std::io::Cursor;
 use std::ops;
@@ -38,6 +39,28 @@ struct Vector3f { x: f32, y: f32, z: f32 }
 #[derive(Clone, Copy, Debug, Default)]
 struct Vector4f { x: f32, y: f32, z: f32, w: f32 }
 
+#[derive(Clone, Copy, Debug, Default)]
+struct Lighting
+{
+    diffuse: Vector3f,
+    specular: Vector3f,
+}
+
+#[derive(Clone, Copy, Debug, Default)]
+struct PointLight
+{
+    position : Vector3f,
+    diffuseColor : Vector3f,
+    diffusePower : f32,
+    specularColor : Vector3f, 
+    specularPower : f32,
+}
+
+fn saturate(v: f32) -> f32 {
+    f32::min(f32::max(v, 0.0), 1.0)
+}
+
+
 fn dot(vec_a: Vector3f, vec_b: Vector3f) -> f32 {
     vec_a.x * vec_b.x + vec_a.y * vec_b.y + vec_a.z * vec_b.z
 }
@@ -50,6 +73,14 @@ fn mult(vec: Vector3f, scalar: f32) -> Vector3f {
     }
 }
 
+fn div(vec: Vector3f, scalar: f32) -> Vector3f {
+    Vector3f {
+        x: vec.x / scalar,
+        y: vec.y / scalar,
+        z: vec.z / scalar,
+    }
+}
+
 fn sub(vec_a: Vector3f, vec_b: Vector3f) -> Vector3f {
     Vector3f {
         x: vec_a.x - vec_b.x,
@@ -66,11 +97,23 @@ fn add(vec_a: Vector3f, vec_b: Vector3f) -> Vector3f {
     }
 }
 
+fn pow(vec: Vector3f, scalar: f32) -> Vector3f {
+    Vector3f {
+        x: f32::powf(vec.x, scalar),
+        y: f32::powf(vec.y, scalar),
+        z: f32::powf(vec.z, scalar),
+    }
+}
+
 fn mix(a: Vector3f, b: Vector3f, mixValue: f32) -> Vector3f
 {
     add(mult(a, (1.0 - mixValue)), mult(b, mixValue))
 }
 
+fn len(vec: Vector3f) -> f32 {
+    (vec.x * vec.x + vec.y * vec.y + vec.z * vec.z).sqrt() as f32
+}
+
 fn normalize(ray: Vector3f) -> Vector3f {
     let multiplier = (ray.x * ray.x + ray.y * ray.y + ray.z * ray.z).sqrt();
     Vector3f {
@@ -115,20 +158,56 @@ fn solve_quadratic(a: f32, b: f32, c: f32, mut x0: f32, mut x1: f32) -> Option<f
     }
 }
 
-fn get_surface_data(phit: Vector3f, nhit: Vector3f, sphere_center: Vector3f) -> Vector2f
+// Return the texture coordinates of the surface hit
+fn get_surface_data(phit: Vector3f, sphere_center: Vector3f) -> (Vector2f, Vector3f)
 {
     let nhit = sub(phit, sphere_center);
     let nhit = normalize(nhit);
-// In this particular case, the normal is simular to a point on a unit sphere
-// centred around the origin. We can thus use the normal coordinates to compute
-// the spherical coordinates of Phit.
-// atan2 returns a value in the range [-pi, pi] and we need to remap it to range [0, 1]
-// acosf returns a value in the range [0, pi] and we also need to remap it to the range [0, 1]
-    Vector2f {
+    // In this particular case, the normal is simular to a point on a unit sphere
+    // centred around the origin. We can thus use the normal coordinates to compute
+    // the spherical coordinates of Phit.
+    // atan2 returns a value in the range [-pi, pi] and we need to remap it to range [0, 1]
+    // acosf returns a value in the range [0, pi] and we also need to remap it to the range [0, 1]
+    (Vector2f { 
         x: (1.0 + (nhit.x).atan2(nhit.z) / PI) * 0.5,
         y: (nhit.y).acos() / PI,
+    }, nhit)
+}
+
+
+fn get_point_light(light: PointLight, pos3D: Vector3f, viewDir: Vector3f, normal: Vector3f) -> Lighting
+{
+    let mut out = Lighting::default();
+    if (light.diffusePower > 0.0)
+    {
+        let lightDir = sub(light.position, pos3D); //3D position in space of the surface
+        let distance = len(lightDir);
+        let lightDir = div(lightDir, distance); // = normalize(lightDir);
+        let distance = distance * distance; //This line may be optimised using Inverse square root
+
+        //Intensity of the diffuse light. Saturate to keep within the 0-1 range.
+        let NdotL = dot(normal, lightDir);
+        let intensity = saturate(NdotL);
+        
+        // Calculate the diffuse light factoring in light color, power and the attenuation
+        out.diffuse = div(mult(mult(light.diffuseColor, intensity), light.diffusePower), distance);
+        
+        //Calculate the half vector between the light vector and the view vector.
+        // This is typically slower than calculating the actual reflection vector
+        // due to the normalize function's reciprocal square root
+        let H = normalize(add(lightDir, viewDir));
+        
+        //Intensity of the specular light
+        let NdotH = dot(normal, H);
+        let intensity = f32::powf(saturate(NdotH), 1.0);
+        
+        //Sum up the specular light factoring
+        out.specular = div(mult(mult(light.specularColor, intensity), light.specularPower), distance); 
     }
+    out
 }
+        
+
 
 fn main() {
     let mut rng = rand::thread_rng();
@@ -194,10 +273,11 @@ fn main() {
         match intersect(orig, dir, sphere_center, radius) {
             None => {}
             Some(t) => {
+                // The point on the circle which we intersected
                 let phit = add(orig, mult(dir, t));
-                let nhit = Vector3f::default();
 
-                let tex = get_surface_data(phit, nhit, sphere_center);
+                // The tex coord & normal at phit 
+                let (tex, nhit) = get_surface_data(phit, sphere_center);
 
                 let scale = 4.0;
 
@@ -212,6 +292,7 @@ fn main() {
                     z: -dir.z,
                 };
 
+                
                 let hit_color = mult(mix(sphere_color, mult(sphere_color, 0.8), f32::max(0.0, dot(nhit, ndir))), pattern);
                 *pixel = image::Rgb([hit_color.x as u8, hit_color.y as u8, hit_color.z as u8]);
             }