From e80e1d09fe142cb9508067a7c8f2b92485aa4a56 Mon Sep 17 00:00:00 2001
From: numzero <numzer0@yandex.ru>
Date: Thu, 20 Nov 2025 14:19:58 +0300
Subject: [PATCH] add interreflections

---
 src/lib.rs             | 49 ++++++++++++++++++++++++------------------
 src/main.rs            |  1 +
 ui/src/api.hxx         |  1 +
 ui/src/main_window.cxx |  1 +
 ui/src/main_window.ui  | 33 ++++++++++++++++++++++++++++
 5 files changed, 64 insertions(+), 21 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index ba7dd7e..8b7384d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -36,6 +36,7 @@ pub struct RedrawArgs {
 	pub light_spread: f32,
 	pub accum_sigma: f32,
 	pub accum_scale: f32,
+	pub reflections: u32,
 	pub show_axes: bool,
 	pub show_shapes: bool,
 	pub show_hit_emission: bool,
@@ -261,29 +262,35 @@ impl Core {
 				}
 			}
 		}
-		let mut hits2: Vec<Hit> = Vec::with_capacity(hits.len());
-		for hit in &hits {
-			let reflector = Lambertian;
-			let reflected = reflector.reflect(&mut prng, hit.normal, hit.incident.dir);
-			let ray = Ray::new(hit.incident.base, reflected);
-			let Some(hit2) = scene.trace_ray(ray) else {
-				continue;
-			};
-			hits2.push(hit2);
-			if args.show_indirect_hit {
-				source_ray_display.extend([
-					Vertex {
-						pos: hit2.incident.base - 0.02 * hit2.incident.dir,
-						color: vec3(1., 0., 1.),
-					},
-					Vertex {
-						pos: hit2.incident.base,
-						color: vec3(1., 1., 1.),
-					},
-				]);
+		if args.reflections > 0 {
+			let mut hits1 = hits.clone();
+			for _ in 0..args.reflections {
+				let mut hits2: Vec<Hit> = Vec::with_capacity(hits1.len());
+				for hit in &hits1 {
+					let reflector = Lambertian;
+					let reflected = reflector.reflect(&mut prng, hit.normal, hit.incident.dir);
+					let ray = Ray::new(hit.incident.base, reflected);
+					let Some(hit2) = scene.trace_ray(ray) else {
+						continue;
+					};
+					hits2.push(hit2);
+					if args.show_indirect_hit {
+						source_ray_display.extend([
+							Vertex {
+								pos: hit2.incident.base - 0.02 * hit2.incident.dir,
+								color: vec3(1., 0., 1.),
+							},
+							Vertex {
+								pos: hit2.incident.base,
+								color: vec3(1., 1., 1.),
+							},
+						]);
+					}
+				}
+				hits.extend(&hits2);
+				hits1 = hits2;
 			}
 		}
-		hits.extend(hits2);
 		let mut camera_ray_display: Vec<Vertex> = Vec::with_capacity(camera_rays.len());
 		if args.show_light {
 			let sigma2 = args.accum_sigma.powi(2);
diff --git a/src/main.rs b/src/main.rs
index 7f8a128..f08bf16 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -52,6 +52,7 @@ impl MainWindow {
 				light_spread: 0.125,
 				accum_sigma: 0.025,
 				accum_scale: 0.01,
+				reflections: 2,
 				show_axes: true,
 				show_shapes: true,
 				show_hit_emission: false,
diff --git a/ui/src/api.hxx b/ui/src/api.hxx
index ff7038e..caf32cd 100644
--- a/ui/src/api.hxx
+++ b/ui/src/api.hxx
@@ -20,6 +20,7 @@ struct RedrawArgs {
 	float light_spread = 0.;
 	float accum_sigma = 1.;
 	float accum_scale = 1.;
+	std::uint32_t reflections = 0;
 	bool show_axes = true;
 	bool show_shapes = true;
 	bool show_hit_emission = true;
diff --git a/ui/src/main_window.cxx b/ui/src/main_window.cxx
index 033645f..dff2f7d 100644
--- a/ui/src/main_window.cxx
+++ b/ui/src/main_window.cxx
@@ -31,6 +31,7 @@ void PhotonLight::updateView() {
 		.light_spread = 0.125,
 		.accum_sigma = exp10f(m_ui->accumSigma->value() / 25.0),
 		.accum_scale = exp10f(m_ui->accumScale->value() / 25.0),
+		.reflections = std::uint32_t(m_ui->reflections->value()),
 		.show_axes = m_ui->displayAxes->isChecked(),
 		.show_shapes = m_ui->displayShapes->isChecked(),
 		.show_hit_emission = m_ui->displayEmitted->isChecked(),
diff --git a/ui/src/main_window.ui b/ui/src/main_window.ui
index 44b57c5..23bf13b 100644
--- a/ui/src/main_window.ui
+++ b/ui/src/main_window.ui
@@ -254,6 +254,23 @@
           </property>
          </widget>
         </item>
+        <item>
+         <widget class="QLabel" name="label">
+          <property name="text">
+           <string>Reflections</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QSpinBox" name="reflections">
+          <property name="maximum">
+           <number>20</number>
+          </property>
+          <property name="value">
+           <number>2</number>
+          </property>
+         </widget>
+        </item>
        </layout>
       </widget>
      </item>
@@ -577,6 +594,22 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>reflections</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateView()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1489</x>
+     <y>712</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>799</x>
+     <y>599</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
  <slots>
   <slot>updateView()</slot>