From 03f27c55debd9a802cf65b7d522a35ca443e0e60 Mon Sep 17 00:00:00 2001
From: Daniel Oom <daoo314@gmail.com>
Date: Wed, 30 Oct 2024 21:59:00 +0100
Subject: [PATCH] Add DirectionalLight to simulate point light infinitely far
 away

---
 kdtree-tester-cli/src/ray_bouncer.rs |  4 +--
 material-tester-cli/src/main.rs      | 12 +++++---
 tracing/src/light.rs                 | 46 +++++++++++++++++++++++-----
 tracing/src/pathtracer.rs            |  4 +--
 4 files changed, 51 insertions(+), 15 deletions(-)

diff --git a/kdtree-tester-cli/src/ray_bouncer.rs b/kdtree-tester-cli/src/ray_bouncer.rs
index 419cd4e..ee2d8b7 100644
--- a/kdtree-tester-cli/src/ray_bouncer.rs
+++ b/kdtree-tester-cli/src/ray_bouncer.rs
@@ -83,8 +83,8 @@ impl RayBouncer {
             .lights
             .iter()
             .filter_map(|light| {
-                let shadow_ray = Ray::between(point_above, light.sample(&mut rng));
-                let shadow = self.checked_ray_intersect(&shadow_ray, 0.0..=1.0);
+                let (shadow_ray, t_range) = light.sample_shadow_ray(point_above, &mut rng);
+                let shadow = self.checked_ray_intersect(&shadow_ray, t_range);
                 (!shadow.is_valid()).then_some(shadow)
             })
             .collect::<Vec<_>>();
diff --git a/material-tester-cli/src/main.rs b/material-tester-cli/src/main.rs
index 6f4159a..6b5a126 100644
--- a/material-tester-cli/src/main.rs
+++ b/material-tester-cli/src/main.rs
@@ -17,7 +17,7 @@ use std::{
 use time::Duration;
 use tracing::{
     camera::{Camera, Pinhole},
-    light::{Light, PointLight},
+    light::{DirectionalLight, Light},
     material::Material,
     pathtracer::Pathtracer,
     worker::render_parallel_iterations,
@@ -172,9 +172,13 @@ fn main() {
     let materials = (0..spheres.len())
         .map(|i| material(i as f32 * 1.0 / (spheres.len() - 1) as f32))
         .collect();
-    let lights = [PointLight {
-        center: Vec3::new(-10.0, -5.0, 1.0) * 100.0,
-        intensity: Vec3::ONE * 100.0 * 100.0f32.powi(2),
+    //let lights = [PointLight {
+    //    center: Vec3::new(-10.0, -5.0, 1.0) * 100.0,
+    //    intensity: Vec3::ONE * 100.0 * 100.0f32.powi(2),
+    //}];
+    let lights = [DirectionalLight {
+        direction: Vec3::new(-1.0, -1.0, 1.0),
+        intensity: Vec3::ONE,
     }];
     let accelerator = NoAccelerator {};
     let pathtracer = Pathtracer {
diff --git a/tracing/src/light.rs b/tracing/src/light.rs
index 5469976..0a4ca49 100644
--- a/tracing/src/light.rs
+++ b/tracing/src/light.rs
@@ -1,3 +1,6 @@
+use std::ops::RangeInclusive;
+
+use geometry::ray::Ray;
 use glam::Vec3;
 use rand::rngs::SmallRng;
 use wavefront::mtl::{self};
@@ -11,9 +14,13 @@ pub struct PointLight {
 }
 
 impl PointLight {
-    pub fn emitted(&self, point: &Vec3) -> Vec3 {
+    fn emitted(&self, point: &Vec3) -> Vec3 {
         self.intensity / (self.center - point).length_squared()
     }
+
+    fn sample(&self) -> (Vec3, RangeInclusive<f32>) {
+        (self.center, 0.0..=1.0)
+    }
 }
 
 #[derive(Clone, Debug)]
@@ -23,8 +30,22 @@ pub struct SphericalLight {
 }
 
 impl SphericalLight {
-    pub fn sample(&self, rng: &mut SmallRng) -> Vec3 {
-        self.point.center + uniform_sample_unit_sphere(rng) * self.radius
+    #[inline]
+    fn sample(&self, rng: &mut SmallRng) -> (Vec3, RangeInclusive<f32>) {
+        let target = self.point.center + uniform_sample_unit_sphere(rng) * self.radius;
+        (target, 0.0..=1.0)
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct DirectionalLight {
+    pub direction: Vec3,
+    pub intensity: Vec3,
+}
+
+impl DirectionalLight {
+    fn sample(&self, point: Vec3) -> (Vec3, RangeInclusive<f32>) {
+        (point - self.direction, 0.0f32..=f32::MAX)
     }
 }
 
@@ -32,21 +53,26 @@ impl SphericalLight {
 pub enum Light {
     PointLight(PointLight),
     SphericalLight(SphericalLight),
+    DirectionalLight(DirectionalLight),
 }
 
 impl Light {
+    #[inline]
     pub fn emitted(&self, point: &Vec3) -> Vec3 {
         match self {
             Light::PointLight(light) => light.emitted(point),
             Light::SphericalLight(light) => light.point.emitted(point),
+            Light::DirectionalLight(light) => light.intensity,
         }
     }
 
-    pub fn sample(&self, rng: &mut SmallRng) -> Vec3 {
-        match self {
-            Light::PointLight(light) => light.center,
+    pub fn sample_shadow_ray(&self, point: Vec3, rng: &mut SmallRng) -> (Ray, RangeInclusive<f32>) {
+        let (target, t_range) = match self {
+            Light::PointLight(light) => light.sample(),
             Light::SphericalLight(light) => light.sample(rng),
-        }
+            Light::DirectionalLight(light) => light.sample(point),
+        };
+        (Ray::between(point, target), t_range)
     }
 }
 
@@ -73,3 +99,9 @@ impl From<SphericalLight> for Light {
         Self::SphericalLight(value)
     }
 }
+
+impl From<DirectionalLight> for Light {
+    fn from(value: DirectionalLight) -> Self {
+        Self::DirectionalLight(value)
+    }
+}
diff --git a/tracing/src/pathtracer.rs b/tracing/src/pathtracer.rs
index 7d372ce..4200cfb 100644
--- a/tracing/src/pathtracer.rs
+++ b/tracing/src/pathtracer.rs
@@ -73,10 +73,10 @@ where
                 .iter()
                 .map(|light| {
                     // TODO: Offset should depend on incoming direction, not only surface normal.
-                    let shadow_ray = Ray::between(point_above, light.sample(rng));
+                    let (shadow_ray, t_range) = light.sample_shadow_ray(point_above, rng);
                     let intersection =
                         self.accelerator
-                            .intersect(&self.geometries, &shadow_ray, 0.0..=1.0);
+                            .intersect(&self.geometries, &shadow_ray, t_range);
                     ray_logger
                         .log_shadow(&shadow_ray, bounce, intersection.is_some())
                         .unwrap();