From a8756debb884ed4ba6e0db271344e22d40f7bfc5 Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Sun, 15 Jan 2023 15:29:52 -0800
Subject: [PATCH] rtiow: precache some things in Triangles.

---
 rtiow/renderer/src/scenes/stltest.rs |  7 +++--
 rtiow/renderer/src/triangles.rs      | 47 ++++++++++++++++------------
 2 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/rtiow/renderer/src/scenes/stltest.rs b/rtiow/renderer/src/scenes/stltest.rs
index a334fca..c8a981d 100644
--- a/rtiow/renderer/src/scenes/stltest.rs
+++ b/rtiow/renderer/src/scenes/stltest.rs
@@ -16,7 +16,7 @@ use crate::{
 };
 
 pub fn new(opt: &Opt) -> Scene {
-    let lookfrom = Vec3::new(200., 200., 200.);
+    let lookfrom = Vec3::new(100., 200., 200.);
     let lookat = Vec3::new(0., 1., 0.);
     let dist_to_focus = 10.0;
     let aperture = 0.0;
@@ -48,9 +48,10 @@ pub fn new(opt: &Opt) -> Scene {
     let light_height = 200.;
     let tri_mesh = Triangles::new(
         &stl_cube,
-        Lambertian::new(ConstantTexture::new(Vec3::new(1., 0., 0.))),
+        Lambertian::new(ConstantTexture::new(Vec3::new(1., 0.1, 0.1))),
+        1.,
     );
-    dbg!(&tri_mesh);
+    dbg!(tri_mesh.triangles.len(), tri_mesh.bbox);
     let objects: Vec<Box<dyn Hit>> = vec![
         // Light from above
         Box::new(XZRect::new(
diff --git a/rtiow/renderer/src/triangles.rs b/rtiow/renderer/src/triangles.rs
index 9cbc2e8..17efbb5 100644
--- a/rtiow/renderer/src/triangles.rs
+++ b/rtiow/renderer/src/triangles.rs
@@ -10,9 +10,14 @@ use crate::{
 
 #[derive(Debug)]
 pub struct Triangle {
-    pub normal: Vec3,
+    normal: Vec3,
+    verts: [Vec3; 3],
+    // Precomputed data
     // TODO(wathiede): precompute `d` on load.
-    pub verts: [Vec3; 3],
+    d: f32,
+    edge0: Vec3,
+    edge1: Vec3,
+    edge2: Vec3,
 }
 
 #[derive(Debug)]
@@ -20,8 +25,8 @@ pub struct Triangles<M>
 where
     M: Material,
 {
-    triangles: Vec<Triangle>,
-    bbox: AABB,
+    pub triangles: Vec<Triangle>,
+    pub bbox: AABB,
     material: M,
 }
 
@@ -29,13 +34,22 @@ impl<M> Triangles<M>
 where
     M: Material,
 {
-    pub fn new(stl: &STL, material: M) -> Triangles<M> {
+    pub fn new(stl: &STL, material: M, scale_factor: f32) -> Triangles<M> {
         let triangles: Vec<_> = stl
             .triangles
             .iter()
-            .map(|t| Triangle {
-                normal: t.normal,
-                verts: t.verts,
+            .map(|t| {
+                let v0 = t.verts[0] * scale_factor;
+                let v1 = t.verts[1] * scale_factor;
+                let v2 = t.verts[2] * scale_factor;
+                Triangle {
+                    normal: t.normal,
+                    verts: [v0, v1, v2],
+                    d: -dot(t.normal, t.verts[0]),
+                    edge0: v1 - v0,
+                    edge1: v2 - v1,
+                    edge2: v0 - v2,
+                }
             })
             .collect();
         let (min, max) = triangles.iter().fold(
@@ -68,11 +82,8 @@ where
     M: Material,
 {
     // Based on https://www.scratchapixel.com/lessons/3d-basic-rendering/ray-tracing-rendering-a-triangle/ray-triangle-intersection-geometric-solution.html
-    fn hit(&self, r: Ray, t_min: f32, t_max: f32) -> Option<HitRecord> {
+    fn hit(&self, r: Ray, _t_min: f32, _t_max: f32) -> Option<HitRecord> {
         for tri in &self.triangles {
-            let v0 = tri.verts[0];
-            let v1 = tri.verts[1];
-            let v2 = tri.verts[2];
             let n = tri.normal;
 
             // close enough to parallel, won't hit
@@ -83,8 +94,7 @@ where
                 continue;
             }
 
-            let d = -dot(n, tri.verts[0]);
-            let t = -(dot(n, r.origin) + d) / n_dot_dir;
+            let t = -(dot(n, r.origin) + tri.d) / n_dot_dir;
             // check if the triangle is behind the ray
             if t < 0. {
                 continue;
@@ -95,23 +105,20 @@ where
             let v1 = tri.verts[1];
             let v2 = tri.verts[2];
 
-            let edge0 = v1 - v0;
             let vp0 = p - v0;
-            let c = cross(edge0, vp0);
+            let c = cross(tri.edge0, vp0);
             if dot(n, c) < 0. {
                 continue;
             }
 
-            let edge1 = v2 - v1;
             let vp1 = p - v1;
-            let c = cross(edge1, vp1);
+            let c = cross(tri.edge1, vp1);
             if dot(n, c) < 0. {
                 continue;
             }
 
-            let edge2 = v0 - v2;
             let vp2 = p - v2;
-            let c = cross(edge2, vp2);
+            let c = cross(tri.edge2, vp2);
             if dot(n, c) < 0. {
                 continue;
             }