ft: 9: diffuse materials

src/vec3.rs

@@ -4,6 +4,8 @@ use std::{
     ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign},
 };
 
+use rand::RngExt;
+
 #[derive(Copy, Clone)]
 pub struct Vec3 {
     r: f32,
@@ -26,6 +28,33 @@ impl Vec3 {
         }
     }
 
+    pub fn random() -> Vec3 {
+        let mut rng = rand::rng();
+        Vec3 {
+            r: rng.random_range(-1.0..1.),
+            g: rng.random_range(-1.0..1.),
+            b: rng.random_range(-1.0..1.),
+        }
+    }
+
+    pub fn random_unit() -> Vec3 {
+        loop {
+            let v = Vec3::random();
+            if v.length_squared() <= 1. {
+                return v / v.length();
+            }
+        }
+    }
+
+    pub fn random_unit_hemisphere(n: &Vec3) -> Vec3 {
+        let v = Vec3::random_unit();
+        if n.dot(&v) > 0.0 {
+            v
+        } else {
+            -v
+        }
+    }
+
     pub fn x(&self) -> &f32 {
         &self.r
     }
@@ -67,9 +96,26 @@ impl Vec3 {
     }
 
     pub fn output(self) -> image::Rgb<u8> {
-        let ir = (255.599 * self.r.clamp(0., 1.)) as u8;
-        let ig = (255.599 * self.g.clamp(0., 1.)) as u8;
-        let ib = (255.599 * self.b.clamp(0., 1.)) as u8;
+        // gamma correction
+        let r = if self.r > 0. {
+            sqrt(self.r).clamp(0., 1.)
+        } else {
+            0.
+        };
+        let g = if self.g > 0. {
+            sqrt(self.g).clamp(0., 1.)
+        } else {
+            0.
+        };
+        let b = if self.b > 0. {
+            sqrt(self.b).clamp(0.1, 1.)
+        } else {
+            0.
+        };
+
+        let ir = (255.599 * r) as u8;
+        let ig = (255.599 * g) as u8;
+        let ib = (255.599 * b) as u8;
 
         image::Rgb([ir, ig, ib])
     }