Add Hittable Triangle

src/hittable.rs

@@ -1,11 +1,11 @@
 use super::{Arc, Color, Material, Metal, Point3, Ray, Vec3};
 
 pub struct HitRecord {
-    pub p: Point3,
-    pub normal: Vec3,
+    pub p: Point3,    // hit location
+    pub normal: Vec3, // normal of hit location
     pub mat_ptr: Arc<dyn Material>,
-    pub t: f64,
-    pub front_face: bool,
+    pub t: f64,           // ray steps (distance) from camera to hit
+    pub front_face: bool, // whether object was hitted from front or back
 }
 
 pub struct Sphere {
@@ -113,39 +113,65 @@ impl Triangle {
 
 impl Hittable for Triangle {
     fn hit(&self, r: &Ray, t_min: f64, t_max: f64, rec: &mut HitRecord) -> bool {
+        let epsilon = 0.0000001;
+
         let a_to_b = self.b - self.a;
         let a_to_c = self.c - self.a;
 
-        let u_vec = Vec3::cross(r.direction(), a_to_c);
+        let h = Vec3::cross(r.direction(), a_to_c);
 
-        let det = Vec3::dot(a_to_b, u_vec);
+        let a = Vec3::dot(a_to_b, h);
 
-        if det < 0.0 { // only positive bound
+        if a > -epsilon && a < epsilon {
+            // ray is parallel to triangle
             return false;
         }
 
-        let inv_det = 1.0 / det;
+        let f = 1.0 / a;
 
         let a_to_origin = r.origin() - self.a;
 
-        let u = Vec3::dot(a_to_origin, u_vec) * inv_det;
+        let u = Vec3::dot(a_to_origin, h) * f;
 
-        if u < 0.0 || u > 1.0 { //check if outside of triangle
+        if u < 0.0 || u > 1.0 {
+            //check if outside of triangle
             return false;
         }
 
-        let v_vec = Vec3::cross(a_to_origin, a_to_b);
+        let q = Vec3::cross(a_to_origin, a_to_b);
 
-        let v = Vec3::dot(r.direction(), v_vec) * inv_det;
+        let v = Vec3::dot(r.direction(), q) * f;
 
-        if v < 0.0 || u+v > 1.0 { // intersection outside of triangle
+        if v < 0.0 || u + v > 1.0 {
+            // intersection outside of triangle
             return false;
         }
 
-        let dist = Vec3::dot(a_to_c, v_vec) * inv_det;
+        let t = Vec3::dot(a_to_c, q) * f; // where is intersection on ray?
 
-        if dist > 0.0 {
+        if t <= epsilon {
+            // line intersection but no ray intersection
+            return false;
+        }
 
+        // ray intersection
+        rec.t = t;
+        rec.p = r.at(t);
+        rec.mat_ptr = self.mat_ptr.clone();
+
+        // triangle normal alg from https://stackoverflow.com/questions/19350792/calculate-normal-of-a-single-triangle-in-3d-space
+        let normal_to_camera = Vec3::new(
+            a_to_b.y() * a_to_c.z() - a_to_b.z() * a_to_c.y(),
+            a_to_b.z() * a_to_c.x() - a_to_b.x() * a_to_c.z(),
+            a_to_b.x() * a_to_c.y() - a_to_b.y() * a_to_c.x(),
+        );
+        let unit_normal = normal_to_camera / normal_to_camera.length();
+        if Vec3::dot(unit_normal, r.direction()) >= 0.0 {
+            // normal towards camera
+            rec.set_face_normal(r, unit_normal);
+        } else {
+            // normal not towards camera, has to be flipped
+            rec.set_face_normal(r, -1.0 * unit_normal);
         }
 
         return true;

src/main.rs

@@ -10,7 +10,7 @@ mod utility;
 mod vec3;
 
 use camera::Camera;
-use hittable::{HitRecord, Hittable, Sphere};
+use hittable::{HitRecord, Hittable, Sphere, Triangle};
 use hittable_list::HittableList;
 use image::{Rgb, RgbImage};
 use material::{Dielectric, Lambertian, Material, Metal};
@@ -57,7 +57,6 @@ fn random_world() -> HittableList {
         material_ground.clone(),
     )));
 
-
     (-6..5).into_iter().for_each(|a| {
         (-6..5).into_iter().for_each(|b| {
             let choose_mat = utility::random_f64();
@@ -138,18 +137,58 @@ fn random_world() -> HittableList {
         material5.clone(),
     )));
 
+    world.add(Box::<Triangle>::new(Triangle::new(
+        Point3::new(0.0, 1.0, 5.0),
+        Point3::new(3.0, 2.0, 0.0),
+        Point3::new(0.0, 4.0, 0.0),
+        material2.clone(),
+    )));
+
+    world.add(Box::<Triangle>::new(Triangle::new(
+        Point3::new(5.0, 1.0, -6.0),
+        Point3::new(1.0, 3.0, -5.0),
+        Point3::new(6.0, 4.0, -6.0),
+        material5.clone(),
+    )));
+    world.add(Box::<Triangle>::new(Triangle::new(
+        Point3::new(5.0, 1.0, -6.0),
+        Point3::new(8.0, 1.0, -7.0),
+        Point3::new(6.0, 4.0, -6.0),
+        material5.clone(),
+    )));
+    world.add(Box::<Triangle>::new(Triangle::new(
+        Point3::new(8.0, 4.0, -5.0),
+        Point3::new(8.0, 1.0, -7.0),
+        Point3::new(6.0, 4.0, -6.0),
+        material5.clone(),
+    )));
+
     return world;
 }
 
+/*
+Current world view:
+
+            I y
+            I
+            I
+            I
+          /   \
+        /       \
+      /           \
+    / z             \ x
+
+*/
+
 fn main() {
     // File
     let mut default_file = "image.ppm";
 
     // Image
     let aspect_ratio = 16.0 / 9.0;
-    let image_width = 600;
+    let image_width = 1200;
     let image_height = (image_width as f64 / aspect_ratio) as u32;
-    let samples_per_pixel = 50_u32;
+    let samples_per_pixel = 100_u32;
     let max_depth = 50;
 
     let vfov = 40.0;