From 5a77b92d9e6dc679931163b57a2b26965dec5192 Mon Sep 17 00:00:00 2001
From: dengqn <someonedeng@qq.com>
Date: Sun, 3 Aug 2025 02:16:05 +0800
Subject: [PATCH] HittableList

---
 src/hittable.rs      | 19 +++++++++++++++++--
 src/image.rs         | 17 +++++++++--------
 src/sphere.rs        | 14 +++++++++-----
 src/types_defined.rs |  6 +++++-
 4 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/src/hittable.rs b/src/hittable.rs
index 765d700..162829f 100644
--- a/src/hittable.rs
+++ b/src/hittable.rs
@@ -1,5 +1,20 @@
 use crate::types_defined::{HitRecord, Ray};
 
 pub trait Hittable {
-    fn hit(self, r: &Ray, t_min: f32, t_max: f32) -> HitRecord;
-}
\ No newline at end of file
+    fn hit(&self, r: &Ray, t_min: f32, t_max: f32) -> HitRecord;
+}
+
+
+pub struct HittableList {
+    pub objects: Vec<Box<dyn Hittable>>
+}
+impl HittableList {
+    pub fn hit(&self, r: &Ray, t_min: f32, t_max: f32) -> Vec<HitRecord> {
+        let mut records = vec![];
+        for object in &self.objects {
+            records.push(object.hit(r, t_min, t_max));
+        }
+        records
+    }
+}
+
diff --git a/src/image.rs b/src/image.rs
index a77b1d0..0c0b1cb 100644
--- a/src/image.rs
+++ b/src/image.rs
@@ -23,7 +23,7 @@ pub fn gen_ray_sphere_normal_ppm_p3(width: i32, height: i32, camera_center: Vec3
              球
              */
             let _sphere_center = Point::new(0.0, 0.0, -1.0);
-            let sphere_radius = 0.5;
+            let sphere_radius = -0.5;
             let sphere = Sphere::new(_sphere_center, sphere_radius);
 
             // determind color
@@ -43,15 +43,16 @@ ray color functions
 fn ray_color<H: Hittable>(r: &Ray, h: H) -> Color {
     let hr = h.hit(&r, 0.0, f32::MAX);
     if hr.t >= 0.0 {
-        let inter_point = hr.p;
-        // 单位向量
-        let n = inter_point / inter_point.dot(inter_point);
-        // 法向量也是 -1～1  +1再x0.5让他落到颜色的区间
-        // return 0.5 * (n - sphere_center + Point::new(1.0, 1.0, 1.0))
-        return 0.5 * (hr.normal + Point::new(1.0, 1.0, 1.0))
+        let normal_color = 0.5 * (hr.normal + Point::new(1.0, 1.0, 1.0));
+        return if hr.front_face {
+            normal_color
+        } else {
+            Color::new(1.0, 1.0, 1.0) - normal_color
+        }
     }
     // v / |v|
     let unit_direction = r.direction / r.direction.length();
     let a = 0.5*(unit_direction.y + 1.0);
-    return (1.0-a)*Color::new(1.0, 1.0, 1.0) + a*Color::new(0.5, 0.7, 1.0);
+    // return background color.
+    (1.0-a)*Color::new(1.0, 1.0, 1.0) + a*Color::new(0.5, 0.7, 1.0)
 }
\ No newline at end of file
diff --git a/src/sphere.rs b/src/sphere.rs
index a63d907..b1fc8e5 100644
--- a/src/sphere.rs
+++ b/src/sphere.rs
@@ -11,7 +11,7 @@ impl Sphere {
 }
 
 impl hittable::Hittable for Sphere {
-    fn hit(self, r: &Ray, t_min: f32, t_max: f32) -> HitRecord {
+    fn hit(&self, r: &Ray, t_min: f32, t_max: f32) -> HitRecord {
         let a: f32 = r.direction.length_squared();
         let h = r.direction.dot(self.center - r.point);
         // let b = -2.0 * r.direction.dot(sphere_center - r.point);
@@ -19,7 +19,7 @@ impl hittable::Hittable for Sphere {
 
         let discriminant = h * h - a * c;
 
-        // // 两个焦点
+        // // 两个交点
         let disc_sqrt = discriminant.sqrt();
         let near = (h - disc_sqrt) / a;
         let far = (h + disc_sqrt) / a;
@@ -31,11 +31,15 @@ impl hittable::Hittable for Sphere {
                 root = -1.0;
             }
         }
-        
+
+        let p = r.at(root);
+        let normal = (p - self.center) / self.radius;
         HitRecord {
             t: root,
-            p: r.at(root),
-            normal: r.at(root) - self.center,
+            // p,
+            normal,
+            // check if r.p inside(>=0) the sphere.
+            front_face: r.direction.dot(normal) < 0.0,
         }
     }
 }
diff --git a/src/types_defined.rs b/src/types_defined.rs
index 5557cc7..b7de5b4 100644
--- a/src/types_defined.rs
+++ b/src/types_defined.rs
@@ -1,6 +1,8 @@
 /*
 * [3]
 */
+use crate::hittable::Hittable;
+
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Vec3 {
     pub x: f32,
@@ -21,11 +23,13 @@ pub struct Ray {
 
 pub struct HitRecord {
     pub t: f32,
-    pub p: Vec3,
+    // pub p: Vec3,
     pub normal: Vec3,
+    pub front_face: bool,
 }
 
 
+
 /*
 /////////////
 // for test