From 1f84cde760546210ee850a4b3119312bc5d7fb67 Mon Sep 17 00:00:00 2001
From: Matthew Gordon <matthew.scott.gordon@gmail.com>
Date: Tue, 5 Oct 2021 09:13:08 -0400
Subject: [PATCH] Make default material sampling cosine-weighted instead of
 uniform

---
 src/materials/mod.rs | 25 +++++--------------------
 1 file changed, 5 insertions(+), 20 deletions(-)

diff --git a/src/materials/mod.rs b/src/materials/mod.rs
index 3590692..00de972 100644
--- a/src/materials/mod.rs
+++ b/src/materials/mod.rs
@@ -1,10 +1,8 @@
 use crate::math::Vec3;
 
 use super::colour::Photon;
+use super::random_distributions::{CosineWeightedHemisphere, RandomDistribution};
 
-use rand::distributions::{Open01, OpenClosed01};
-use rand::{thread_rng, Rng};
-use std::f64::consts::PI;
 use std::fmt::Debug;
 
 pub mod lambertian_material;
@@ -28,22 +26,9 @@ pub trait Material: Debug + Sync + Send {
     fn bsdf<'a>(&'a self) -> Box<dyn Fn(&Vec3, &Vec3, &Photon) -> Photon + 'a>;
 
     fn sample(&self, _w_i: &Vec3, _photon: &Photon) -> MaterialSampleResult {
-        let mut rng = thread_rng();
-        let mut w_o = Vec3::new(
-            2.0 * rng.sample::<f64, _>(Open01) - 1.0,
-            2.0 * rng.sample::<f64, _>(Open01) - 1.0,
-            rng.sample::<f64, _>(OpenClosed01),
-        );
-        while w_o.norm_squared() > 1.0 {
-            w_o = Vec3::new(
-                2.0 * rng.sample::<f64, _>(Open01) - 1.0,
-                2.0 * rng.sample::<f64, _>(Open01) - 1.0,
-                rng.sample::<f64, _>(OpenClosed01),
-            );
-        }
-        MaterialSampleResult {
-            direction: w_o.normalize(),
-            pdf: 1.0 / (2.0 * PI),
-        }
+        let distribution = CosineWeightedHemisphere::new();
+        let direction = distribution.value();
+        let pdf = distribution.pdf(direction);
+        MaterialSampleResult { direction, pdf }
     }
 }