From e3009563ba9f9018200d8b8cc20f3b3f41ff0dba Mon Sep 17 00:00:00 2001
From: hal8174 <henning.lindemann@pm.me>
Date: Sat, 24 May 2025 22:45:46 +0200
Subject: [PATCH] Fix nans for iridescent material

---
 ray-tracing-material/src/iridescent.rs        | 46 ++++++++++++++++---
 ray-tracing-scene/src/examples/mod.rs         |  2 +-
 .../src/examples/stanford_dragon.rs           |  4 +-
 3 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/ray-tracing-material/src/iridescent.rs b/ray-tracing-material/src/iridescent.rs
index df667cd..a29f2cb 100644
--- a/ray-tracing-material/src/iridescent.rs
+++ b/ray-tracing-material/src/iridescent.rs
@@ -49,6 +49,13 @@ impl Iridescent {
         let imag = (num_imag * denom_real - num_real * denom_imag)
             / (denom_real * denom_real + denom_imag * denom_imag);
 
+        if !real.is_normal() || !imag.is_normal() {
+            dbg!(
+                l, theta1, theta2, s_polaized, r12, phi, num_real, num_imag, denom_real,
+                denom_imag, real, imag
+            );
+        }
+
         real * real + imag * imag
     }
 
@@ -91,10 +98,12 @@ impl Iridescent {
             ));
         }
 
-        if local_cos_k_delta.abs() <= 1.0 {
+        if local_cos_k_delta.abs() < 1.0 {
             let k_delta = f32::acos(local_cos_k_delta);
 
-            if !k_delta.is_normal() {
+            let u = f32::sin(k_delta) / f32::sin(self.n * k_delta);
+
+            if !k_delta.is_normal() || !u.is_normal() {
                 dbg!((
                     l,
                     theta1,
@@ -103,17 +112,19 @@ impl Iridescent {
                     local_c_squred,
                     s_polaized,
                     k_delta,
+                    u,
                 ));
             }
-            let u = f32::sin(k_delta) / f32::sin(self.n * k_delta);
 
             local_c_squred / (local_c_squred + u * u)
-        } else {
+        } else if local_cos_k_delta.abs() > 1.0 {
             let imk_delta = -f32::ln(f32::abs(
                 local_cos_k_delta - f32::sqrt(local_cos_k_delta * local_cos_k_delta - 1.0),
             ));
 
-            if !imk_delta.is_normal() {
+            let u = f32::sinh(imk_delta) / f32::sinh(self.n * imk_delta);
+
+            if !imk_delta.is_normal() || !u.is_normal() {
                 dbg!((
                     l,
                     theta1,
@@ -122,9 +133,25 @@ impl Iridescent {
                     local_c_squred,
                     s_polaized,
                     imk_delta,
+                    u
+                ));
+            }
+
+            local_c_squred / (local_c_squred + u * u)
+        } else {
+            let u = 1.0 / self.n;
+
+            if !u.is_normal() {
+                dbg!((
+                    l,
+                    theta1,
+                    theta2,
+                    local_cos_k_delta,
+                    local_c_squred,
+                    s_polaized,
+                    u
                 ));
             }
-            let u = f32::sinh(imk_delta) / f32::sinh(self.n * imk_delta);
 
             local_c_squred / (local_c_squred + u * u)
         }
@@ -194,7 +221,12 @@ impl<R: Rng> Material<R> for Iridescent {
     fn sample(&self, w_in: Dir3, rng: &mut R) -> ray_tracing_core::material::SampleResult {
         let w_out = (2.0 * Dir3::up() * w_in.y()) - w_in;
 
-        let color = self.monte_carlo_reflectance(f32::acos(w_out.z()), rng);
+        let color = if w_out.y() > 0.0 && w_out.y() <= 1.0 {
+            self.monte_carlo_reflectance(f32::acos(w_out.y()), rng)
+        } else {
+            // dbg!(w_out);
+            Color::black()
+        };
 
         ray_tracing_core::material::SampleResult::new(w_out, color, true)
     }
diff --git a/ray-tracing-scene/src/examples/mod.rs b/ray-tracing-scene/src/examples/mod.rs
index 327d832..3c4fea3 100644
--- a/ray-tracing-scene/src/examples/mod.rs
+++ b/ray-tracing-scene/src/examples/mod.rs
@@ -28,7 +28,7 @@ pub fn example_scenes<R: Rng + Debug + 'static>() -> HashMap<&'static str, Box<d
         "stanford_dragon_microfacet",
         Box::new(stanford_dragon::StanfordDragon::new(material)),
     );
-    let material = Iridescent::new(300.0, 300.0, 1.0, 1.5, 10);
+    let material = Iridescent::new(100.0, 900.0, 1.0, 1.5, 20);
     map.insert(
         "stanford_dragon_iridescent",
         Box::new(stanford_dragon::StanfordDragon::new(material)),
diff --git a/ray-tracing-scene/src/examples/stanford_dragon.rs b/ray-tracing-scene/src/examples/stanford_dragon.rs
index e263d53..80179d5 100644
--- a/ray-tracing-scene/src/examples/stanford_dragon.rs
+++ b/ray-tracing-scene/src/examples/stanford_dragon.rs
@@ -40,8 +40,8 @@ impl<R: Rng + 'static, M: Material<R> + 'static> ExampleScene<R> for StanfordDra
             let materials = vec![
                 BVHMaterial::new_material(self.material.take().unwrap()),
                 BVHMaterial::new_material(OrenNayar::new(0.5, Color::new(0.8, 0.8, 0.8))),
-                BVHMaterial::new_material(OrenNayar::new(0.5, Color::new(0.9, 0.0, 0.0))),
-                BVHMaterial::new_material(OrenNayar::new(0.5, Color::new(0.0, 0.9, 0.0))),
+                BVHMaterial::new_material(OrenNayar::new(0.5, Color::new(0.9, 0.2, 0.2))),
+                BVHMaterial::new_material(OrenNayar::new(0.5, Color::new(0.2, 0.9, 0.2))),
                 BVHMaterial::new_light(AreaLight::new(Color::white() * 30.0)),
             ];