Fix iridescent material

ray-tracing-material-visualizer/src/bin/iridescent.rs

@@ -1,17 +1,40 @@
 use core::f32;
 
-use plotters::{prelude::*, style::full_palette::GREEN};
+use plotters::{coord::Shift, prelude::*, style::full_palette::GREEN};
 use rand::{rngs::SmallRng, Rng, SeedableRng};
 use ray_tracing_material::iridescent::Iridescent;
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let root = BitMapBackend::new("iridescent_sweep.png", (800, 600)).into_drawing_area();
+    let root = BitMapBackend::new("iridescent_sweep.png", (2200, 1200)).into_drawing_area();
 
     root.fill(&WHITE)?;
-    let mut chart = ChartBuilder::on(&root)
+
+    let d = root.split_evenly((3, 5));
+
+    let ds = [0.1, 0.3, 0.5, 0.7, 0.9];
+    let deltas = [244.0, 500.0, 988.0];
+
+    for (i, c) in d.into_iter().enumerate() {
+        draw_subplot(deltas[i / 5], 1.0 - ds[i % 5], &c)?;
+    }
+
+    root.present()?;
+
+    Ok(())
+}
+
+fn draw_subplot<DB: DrawingBackend>(
+    delta: f32,
+    d2: f32,
+    c: &DrawingArea<DB, Shift>,
+) -> Result<(), Box<dyn std::error::Error>>
+where
+    <DB as plotters::prelude::DrawingBackend>::ErrorType: 'static,
+{
+    let mut chart = ChartBuilder::on(c)
         .margin(5)
         .x_label_area_size(30)
         .y_label_area_size(30)
-        .build_cartesian_2d(0f32..f32::consts::FRAC_PI_2, 0f32..1f32)?;
+        .build_cartesian_2d(0f32..f32::consts::FRAC_PI_2, 0f32..1.1f32)?;
 
     chart.configure_mesh().draw()?;
 
@@ -20,7 +43,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let height_per_pixel = 1.0 / (pixel_range_y.end - pixel_range_y.start) as f32;
     let samples = 10000;
 
-    let m = Iridescent::new(0.5 * 244.0, 0.5 * 244.0, 1.0, 1.5, 20);
+    let m = Iridescent::new((1.0 - d2) * delta, d2 * delta, 1.0, 1.5, 20);
 
     let mut data = Vec::new();
 
@@ -38,10 +61,16 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             );
             s += m.monte_carlo_reflectance(theta1, &mut rng);
             s_wavelength += ray_tracing_core::color::Color::new(
-                m.averaged_reflectance(595.0, theta1),
+                m.averaged_reflectance(599.0, theta1),
                 m.averaged_reflectance(556.0, theta1),
                 m.averaged_reflectance(442.0, theta1),
             );
+            // let theta2 = f32::asin(f32::sin(theta1) * 1.0 / 1.5);
+            // s_wavelength += ray_tracing_core::color::Color::new(
+            //     m.abs_C_squared(599.0, theta1, theta2, false),
+            //     m.abs_C_squared(556.0, theta1, theta2, false),
+            //     m.abs_C_squared(442.0, theta1, theta2, false),
+            // );
         }
 
         let c = s / samples as f32;
@@ -49,12 +78,12 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         // data.push(c);
         data.push(s_wavelength / samples as f32);
         // dbg!(c);
-        for j in 0..10 {
+        for j in 0..20 {
             plotting_area
                 .draw_pixel(
                     (
                         f32::consts::FRAC_PI_2 * (i as f32 / buckets as f32),
-                        1.0 - (height_per_pixel * (j as f32)),
+                        1.1 - (height_per_pixel * (j as f32)),
                     ),
                     &RGBColor(
                         (c.r() * 256.0) as u8,
@@ -96,7 +125,5 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         &BLUE,
     ))?;
 
-    root.present()?;
-
     Ok(())
 }

ray-tracing-material/src/iridescent.rs

@@ -22,26 +22,24 @@ impl Iridescent {
         }
     }
 
-    fn fresnel_reflection(&self, theta1: f32, theta2: f32, s_polaized: bool) -> f32 {
+    fn fresnel_reflection(n1: f32, n2: f32, theta1: f32, theta2: f32, s_polaized: bool) -> f32 {
         if s_polaized {
-            (self.n1 * theta1.cos() - self.n2 * theta2.cos())
-                / (self.n1 * theta1.cos() + self.n2 * theta2.cos())
+            (n1 * theta1.cos() - n2 * theta2.cos()) / (n1 * theta1.cos() + n2 * theta2.cos())
         } else {
-            (self.n2 * theta1.cos() - self.n1 * theta2.cos())
-                / (self.n2 * theta1.cos() + self.n1 * theta2.cos())
+            (n2 * theta1.cos() - n1 * theta2.cos()) / (n2 * theta1.cos() + n1 * theta2.cos())
         }
     }
 
     fn abs_r_1_squared(&self, l: f32, theta1: f32, theta2: f32, s_polaized: bool) -> f32 {
-        let r12 = self.fresnel_reflection(theta1, theta2, s_polaized);
+        let r12 = Self::fresnel_reflection(self.n1, self.n2, theta1, theta2, s_polaized);
 
         let phi = 2.0 * f32::consts::PI * self.n2 * self.d2 * theta2.cos() / l;
 
         let num_real = r12 * (1.0 - f32::cos(-2.0 * phi));
-        let num_imag = r12 * (1.0 - f32::sin(-2.0 * phi));
+        let num_imag = r12 * (-1.0 * f32::sin(-2.0 * phi));
 
         let denom_real = 1.0 - r12 * r12 * f32::cos(-2.0 * phi);
-        let denom_imag = 1.0 - r12 * r12 * f32::sin(-2.0 * phi);
+        let denom_imag = 0.0 - r12 * r12 * f32::sin(-2.0 * phi);
 
         let real = (num_real * denom_real + num_imag * denom_imag)
             / (denom_real * denom_real + denom_imag * denom_imag);
@@ -59,10 +57,10 @@ impl Iridescent {
         real * real + imag * imag
     }
 
-    fn abs_C_squared(&self, l: f32, theta1: f32, theta2: f32, s_polaized: bool) -> f32 {
+    pub fn abs_C_squared(&self, l: f32, theta1: f32, theta2: f32, s_polaized: bool) -> f32 {
         let local_abs_r_1_squared = self.abs_r_1_squared(l, theta1, theta2, s_polaized);
 
-        local_abs_r_1_squared / (local_abs_r_1_squared + 1.0)
+        local_abs_r_1_squared / (1.0 - local_abs_r_1_squared)
     }
 
     fn cos_K_Delta(&self, l: f32, theta1: f32, theta2: f32, s_polaized: bool) -> f32 {