From b64c7e972c52b7d015d661866f0cf902370343e5 Mon Sep 17 00:00:00 2001
From: Julian T <julian@jtle.dk>
Date: Sat, 6 Feb 2021 23:43:06 +0100
Subject: Implement pathtracing

---
 src/trace/mod.rs       | 26 +++++++++++++++++++-------
 src/trace/pathtrace.rs | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+), 7 deletions(-)
 create mode 100644 src/trace/pathtrace.rs

(limited to 'src/trace')

diff --git a/src/trace/mod.rs b/src/trace/mod.rs
index 9c8b0b8..7f02f6f 100644
--- a/src/trace/mod.rs
+++ b/src/trace/mod.rs
@@ -1,24 +1,36 @@
 use crate::scene::Scene;
 use crate::core::{Spectrum, Ray, Vector3f};
+use crate::sample::Sampler;
+
+mod pathtrace;
+pub use pathtrace::PathTracer;
 
 /// Simple surface normal tracer
 ///
 /// This ray tracer bases color values on the hit surface normals
-pub struct NormTracer {}
+pub struct NormTracer<'a> {
+    scn: &'a Scene,
+}
 
 /// Alias for chosen trace implementation.
 ///
 /// This is swiched at compile time to save alot of time.
-pub type Tracer = NormTracer;
+pub type DefaultTracer<'a> = PathTracer<'a>;
 
-impl NormTracer {
-    pub fn new() -> NormTracer {
-        NormTracer {}
+pub trait Tracer {
+    fn trace(&self, sampler: &mut dyn Sampler, ray: &Ray) -> Spectrum;
+}
+
+impl NormTracer<'_> {
+    pub fn new(scn: &Scene) -> NormTracer {
+        NormTracer {scn}
     }
+}
 
-    pub fn trace(&self, scn: &Scene, ray: &Ray) -> Spectrum {
+impl Tracer for NormTracer<'_> {
+    fn trace(&self, sampler: &mut dyn Sampler, ray: &Ray) -> Spectrum {
         // Trace ray
-        if let Some(i) = scn.intersect(ray) {
+        if let Some(i) = self.scn.intersect(ray) {
             let norm = i.n * 0.5 + Vector3f::new(0.5);
 
             return Spectrum::new_rgb(norm.x, norm.y, norm.z);
diff --git a/src/trace/pathtrace.rs b/src/trace/pathtrace.rs
new file mode 100644
index 0000000..32a8e15
--- /dev/null
+++ b/src/trace/pathtrace.rs
@@ -0,0 +1,41 @@
+use crate::scene::Scene;
+use crate::core::{Ray, Spectrum};
+use crate::sample::Sampler;
+use super::Tracer;
+
+pub struct PathTracer<'a> {
+    depth: i32,
+    scn: &'a Scene,
+}
+
+impl PathTracer<'_> {
+    pub fn new(scn: &Scene, depth: Option<i32>) -> PathTracer {
+        let depth = depth.unwrap_or(-1);
+
+        PathTracer {
+            depth,
+            scn,
+        }
+    }
+
+    pub fn trace_recur(&self, sampler: &mut dyn Sampler, ray: &Ray) -> Spectrum {
+
+        if let Some(i) = self.scn.intersect(ray) {
+            // Get a random direction in the hemisphere a i.p
+            // This is Lambertian reflection
+            let target = i.p + i.n + sampler.get_unit_vector();
+            return self.trace_recur(sampler, &Ray::new_to(i.p, target)) * 0.5;
+        }
+
+        // Simulates a sky
+        let t = (ray.direction.norm().y + 1.0) * 0.5;
+        Spectrum::new_rgb(1.0, 1.0, 1.0) * (1.0-t) + Spectrum::new_rgb(0.5, 0.7, 1.0) * t
+
+    }
+}
+
+impl Tracer for PathTracer<'_> {
+    fn trace(&self, sampler: &mut dyn Sampler, ray: &Ray) -> Spectrum {
+        self.trace_recur(sampler, ray)
+    }
+}
-- 
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