From 88cda66f0c8a6376ead672637ba92f18ee3e7040 Mon Sep 17 00:00:00 2001
From: Daniel Oom <daoo314@gmail.com>
Date: Thu, 5 Sep 2024 21:25:59 +0200
Subject: [PATCH] Clean-up scene intersection lookup code

---
 kdtree-tester-cli/src/ray_bouncer.rs | 19 +++++++--------
 scene/src/lib.rs                     | 36 +++++++++++++++-------------
 tracing/src/pathtracer.rs            | 12 ++++------
 3 files changed, 32 insertions(+), 35 deletions(-)

diff --git a/kdtree-tester-cli/src/ray_bouncer.rs b/kdtree-tester-cli/src/ray_bouncer.rs
index 108b584..2268074 100644
--- a/kdtree-tester-cli/src/ray_bouncer.rs
+++ b/kdtree-tester-cli/src/ray_bouncer.rs
@@ -61,16 +61,17 @@ impl RayBouncer {
         if !intersection.is_valid() {
             return Some(intersection);
         };
-        let intersection = intersection.reference?;
-        let intersection_index = intersection.index;
-        let intersection = intersection.inner;
+        let intersection = self
+            .scene
+            .lookup_intersection(intersection.reference.unwrap());
 
         let wi = -ray.direction;
-        let n = self.scene.get_normal(intersection_index, &intersection);
-        let uv = self.scene.get_texcoord(intersection_index, &intersection);
+        let n = intersection.normal;
+        let uv = intersection.texcoord;
+        let material = intersection.material;
         // TODO: How to chose offset?
         let offset = 0.00001 * n;
-        let point = ray.param(intersection.t);
+        let point = ray.param(intersection.inner.inner.t);
         let point_above = point + offset;
         let point_below = point - offset;
 
@@ -88,11 +89,7 @@ impl RayBouncer {
             return Some(checked.clone());
         }
 
-        let sample = material_sample(
-            self.scene.get_material(intersection_index),
-            &IncomingRay { wi, n, uv },
-            &mut rng,
-        );
+        let sample = material_sample(material, &IncomingRay { wi, n, uv }, &mut rng);
         let next_ray = Ray::new(
             if sample.wo.dot(n) >= 0.0 {
                 point_above
diff --git a/scene/src/lib.rs b/scene/src/lib.rs
index 33a4fbc..db3b3ed 100644
--- a/scene/src/lib.rs
+++ b/scene/src/lib.rs
@@ -1,4 +1,4 @@
-use geometry::{geometry::Geometry, intersection::RayIntersection, triangle::Triangle};
+use geometry::{geometry::Geometry, intersection::GeometryIntersection, triangle::Triangle};
 use glam::{Vec2, Vec3};
 use material::Material;
 use std::{collections::BTreeMap, fs::File, io::BufReader, path::Path};
@@ -108,6 +108,13 @@ fn collect_lights(mtl: &mtl::Mtl) -> Vec<SphericalLight> {
         .collect()
 }
 
+pub struct SceneIntersection<'a> {
+    pub inner: GeometryIntersection,
+    pub material: &'a Material,
+    pub normal: Vec3,
+    pub texcoord: Vec2,
+}
+
 impl Scene {
     pub fn from_wavefront(image_directory: &Path, obj: &obj::Obj, mtl: &mtl::Mtl) -> Scene {
         let materials = materials_from_mtl(image_directory, mtl);
@@ -203,21 +210,16 @@ impl Scene {
     }
 
     #[inline]
-    pub fn get_material(&self, index: u32) -> &Material {
-        &self.materials[self.properties[index as usize].material_index]
-    }
-
-    #[inline]
-    pub fn get_normal(&self, index: u32, intersection: &RayIntersection) -> Vec3 {
-        self.properties[index as usize]
-            .normals
-            .lerp(intersection.u, intersection.v)
-    }
-
-    #[inline]
-    pub fn get_texcoord(&self, index: u32, intersection: &RayIntersection) -> Vec2 {
-        self.properties[index as usize]
-            .texcoords
-            .lerp(intersection.u, intersection.v)
+    pub fn lookup_intersection(&self, inner: GeometryIntersection) -> SceneIntersection<'_> {
+        let properties = &self.properties[inner.index as usize];
+        let normal = properties.normals.lerp(inner.inner.u, inner.inner.v);
+        let texcoord = properties.texcoords.lerp(inner.inner.u, inner.inner.v);
+        let material = &self.materials[properties.material_index];
+        SceneIntersection {
+            inner,
+            material,
+            normal,
+            texcoord,
+        }
     }
 }
diff --git a/tracing/src/pathtracer.rs b/tracing/src/pathtracer.rs
index 136c433..0702007 100644
--- a/tracing/src/pathtracer.rs
+++ b/tracing/src/pathtracer.rs
@@ -41,20 +41,18 @@ impl Pathtracer {
             if intersection.is_none() {
                 return accumulated_radiance + accumulated_transport * self.scene.environment();
             }
-            let intersection = intersection.unwrap();
-            let intersection_index = intersection.index;
-            let intersection = intersection.inner;
+            let intersection = self.scene.lookup_intersection(intersection.unwrap());
 
             let wi = -ray.direction;
-            let n = self.scene.get_normal(intersection_index, &intersection);
-            let uv = self.scene.get_texcoord(intersection_index, &intersection);
-            let material = self.scene.get_material(intersection_index);
+            let n = intersection.normal;
+            let uv = intersection.texcoord;
+            let material = intersection.material;
 
             // TODO: How to chose offset?
             // In PBRT the offset is chosen based on the surface normal, surface intersection
             // calculation error, sampled incoming direction and then rounded up to the next float.
             let offset = 0.00001 * n;
-            let point = ray.param(intersection.t);
+            let point = ray.param(intersection.inner.inner.t);
             let point_above = point + offset;
             let point_below = point - offset;