From 3cb3e4a8faf037165f66dd60a533b4600454d850 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20R=C3=B6ger?= <jonas.roeger@tu-dortmund.de>
Date: Tue, 31 Mar 2026 23:01:55 +0200
Subject: [PATCH] feat(sphere): inner intersection

---
 scenes/demo-2.lisp      | 45 ++++++++++++++++++++++++-----------------
 src/raytracer/sphere.rs | 23 +++++++++++++++------
 2 files changed, 44 insertions(+), 24 deletions(-)

diff --git a/scenes/demo-2.lisp b/scenes/demo-2.lisp
index f8b188d..09c76c3 100644
--- a/scenes/demo-2.lisp
+++ b/scenes/demo-2.lisp
@@ -29,6 +29,13 @@
       (color 0.6 0.6 0.6)
       100 0.5))
 
+(set 'dark-mirror
+     (material
+      (color 0 0 0)
+      (color 0 0 0)
+      (color 0.2 0.2 0.2)
+      20 0.6))
+
 (set 's1
      (sphere
       (point 0 1 0) 1 blue))
@@ -36,22 +43,26 @@
      (sphere
       (point 2 0.5 2) 0.5 green))
 
-(defun spiral-sphere (i n)
+(set 'mirror-dome
+     (sphere
+      (point 0 -30 0)
+      100 dark-mirror))
+
+(defun spiral-sphere (i n t)
   (sphere
    (progn
-     (print "Spiral Sphere at: ")
-     (println (point
-               (* 2 (cos (/ (* i 6.2) n)))
-               0.5
-               (* 2 (sin (/ (* i 6.2) n)))))
+     (point
+      (* 2 (cos (/ (* i 6.2) n)))
+      (+ 0.5 (* 0.3 (cos (+ (/ (* i 6.2) n) (/ t 5.0)))))
+      (* 2 (sin (/ (* i 6.2) n))))
      )
-   0.5 red))
+   0.2 red))
 
-(defun spiral (scn i n)
+(defun spiral (scn i n t)
   (if (< i n)
       (scene-add
-       (spiral scn (+ i 1) n)
-       (spiral-sphere i n))
+       (spiral scn (+ i 1) n t)
+       (spiral-sphere i n t))
       scn))
 
 (set 'p1
@@ -67,22 +78,20 @@
 
 (set 'scn-base (scene
                 (color 0.1 0.1 0.1)
-                '(s1 s2 p1)
+                '(s1 s2 p1 mirror-dome)
                 '(l1 l2)))
 
-(set 'scn (spiral scn-base 0 10))
-
 (set 'cam (camera (point 0 3 6) (point 0 0 0) (vector 0 1 0) 40 1920 1080))
 
 (defun scene-fn (t)
-  scn)
+  (spiral scn-base 0 30 t))
 
 (defun cam-fn (t c)
-  (let '((pos . (point 0 4 8))
+  (let '((pos . (point -3 0.5 8))
          (cnt . (point 0 0 0))
-         (to . (point -2 3 -6))
+         (to . (point -3 0.5 -8))
          (up . (vector 0 1 0))
-         (fovy . 40)
+         (fovy . 80)
          (pct . (/ t 300.0)))
     (let '((tpos . (vadd pos (vmul (vsub to pos) pct)))
            (tfovy . (+ fovy (* 40 pct)))
@@ -91,4 +100,4 @@
       )
     ))
 
-(render-animation cam "demo-animation-2.mp4" scene-fn cam-fn 300 30 4 2)
+(render-animation cam "demo-animation.mp4" scene-fn cam-fn 400 30 4 2)
diff --git a/src/raytracer/sphere.rs b/src/raytracer/sphere.rs
index 8627456..ade2c21 100644
--- a/src/raytracer/sphere.rs
+++ b/src/raytracer/sphere.rs
@@ -1,3 +1,5 @@
+use nalgebra::distance;
+
 use super::types::{Intersect, Material, Point3, Ray, Scalar, Vector3};
 
 extern crate nalgebra as na;
@@ -52,12 +54,21 @@ impl Intersect for Sphere {
             if t < Scalar::MAX {
                 let isect_pt: Point3 = ray.origin + ray.direction * t;
 
-                return Some((
-                    isect_pt,
-                    (isect_pt - self.center) / self.radius,
-                    t,
-                    self.material.clone(),
-                ));
+                if c >= 0.0 {
+                    return Some((
+                        isect_pt,
+                        (isect_pt - self.center) / self.radius,
+                        t,
+                        self.material.clone(),
+                    ));
+                } else {
+                    return Some((
+                        isect_pt,
+                        -(isect_pt - self.center) / self.radius,
+                        t,
+                        self.material.clone(),
+                    ));
+                }
             }
         }