diff --git a/src/lib.rs b/src/lib.rs
index f2f9c39..18937dd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -27,6 +27,13 @@ pub struct SphericalPosition {
 	pub distance: f32,
 }
 
+#[derive(Debug, Clone, Copy)]
+#[repr(u8)]
+pub enum UseNormal {
+	Light,
+	Camera,
+}
+
 #[derive(Debug, Clone, Copy)]
 #[repr(C)]
 pub struct RedrawArgs {
@@ -36,7 +43,8 @@ pub struct RedrawArgs {
 	pub light_spread: f32,
 	pub accum_sigma: f32,
 	pub accum_scale: f32,
-	pub reflections: u32,
+	pub reflections: u8,
+	pub use_normal: UseNormal,
 	pub show_axes: bool,
 	pub show_shapes: bool,
 	pub show_hit_emission: bool,
@@ -305,12 +313,15 @@ impl Core {
 					if d2 > 9. * sigma2 {
 						continue;
 					}
-					assert!(hit.normal.is_normalized());
+					let normal = match args.use_normal {
+						UseNormal::Light => light_hit.normal,
+						UseNormal::Camera => hit.normal,
+					};
+					assert!(normal.is_normalized());
 					assert!(hit.incident.dir.is_normalized());
 					let reflector = Lambertian;
 					let in_lm = 1.0;
-					let out_cd =
-						in_lm * reflector.brdf(light_hit.normal, light_hit.incident.dir, -ray.dir);
+					let out_cd = in_lm * reflector.brdf(normal, light_hit.incident.dir, -ray.dir);
 					let weight = accum_normalizator * (-0.5 * d2 / sigma2).exp();
 					total_cd += weight * out_cd;
 				}
diff --git a/src/main.rs b/src/main.rs
index f08bf16..cb11049 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,7 @@
 use std::{f32::consts::PI, sync::Arc};
 
 use glam::uvec2;
-use photon_light::{Core, RedrawArgs, SphericalPosition, init_gpu_inner};
+use photon_light::{Core, RedrawArgs, SphericalPosition, UseNormal, init_gpu_inner};
 use winit::{
 	application::ApplicationHandler,
 	event::WindowEvent,
@@ -53,6 +53,7 @@ impl MainWindow {
 				accum_sigma: 0.025,
 				accum_scale: 0.01,
 				reflections: 2,
+				use_normal: UseNormal::Light,
 				show_axes: true,
 				show_shapes: true,
 				show_hit_emission: false,
diff --git a/ui/src/api.hxx b/ui/src/api.hxx
index caf32cd..bc96bc8 100644
--- a/ui/src/api.hxx
+++ b/ui/src/api.hxx
@@ -13,6 +13,11 @@ struct SphericalPosition {
 	float distance = 1.;
 };
 
+enum class UseNormal: std::uint8_t {
+	Light,
+	Camera,
+};
+
 struct RedrawArgs {
 	SphericalPosition camera_position;
 	SphericalPosition light_position;
@@ -20,7 +25,8 @@ struct RedrawArgs {
 	float light_spread = 0.;
 	float accum_sigma = 1.;
 	float accum_scale = 1.;
-	std::uint32_t reflections = 0;
+	std::uint8_t reflections = 0;
+	UseNormal use_normal = UseNormal::Light;
 	bool show_axes = true;
 	bool show_shapes = true;
 	bool show_hit_emission = true;
@@ -31,6 +37,7 @@ struct RedrawArgs {
 };
 } // namespace ffi
 
+using ffi::UseNormal;
 using ffi::RedrawArgs;
 using ffi::SphericalPosition;
 
diff --git a/ui/src/main_window.cxx b/ui/src/main_window.cxx
index dff2f7d..11ae0f2 100644
--- a/ui/src/main_window.cxx
+++ b/ui/src/main_window.cxx
@@ -16,6 +16,11 @@ float deg_to_rad(float val) {
 }
 
 void PhotonLight::updateView() {
+	UseNormal use_normal = {};
+	if (m_ui->normalFromLight->isChecked())
+		use_normal = UseNormal::Light;
+	else if (m_ui->normalFromCamera->isChecked())
+		use_normal = UseNormal::Camera;
 	RedrawArgs args{
 		.camera_position = SphericalPosition{
 			.yaw = deg_to_rad(m_ui->cameraYaw->value()),
@@ -31,7 +36,8 @@ 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()),
+		.reflections = std::uint8_t(m_ui->reflections->value()),
+		.use_normal = use_normal,
 		.show_axes = m_ui->displayAxes->isChecked(),
 		.show_shapes = m_ui->displayShapes->isChecked(),
 		.show_hit_emission = m_ui->displayEmitted->isChecked(),
@@ -51,4 +57,9 @@ void PhotonLight::updateView() {
 	m_ui->viewport->setView(args);
 }
 
+void PhotonLight::updateViewIf(bool update) {
+	if (update)
+		updateView();
+}
+
 #include "moc_main_window.cpp"
diff --git a/ui/src/main_window.hxx b/ui/src/main_window.hxx
index 1ca73cc..27b63ff 100644
--- a/ui/src/main_window.hxx
+++ b/ui/src/main_window.hxx
@@ -16,6 +16,7 @@ public:
 
 public slots:
 	void updateView();
+	void updateViewIf(bool update); // for radio buttons
 
 private:
 	const std::unique_ptr<Ui::MainWindow> m_ui;
diff --git a/ui/src/main_window.ui b/ui/src/main_window.ui
index 697c566..5802a1d 100644
--- a/ui/src/main_window.ui
+++ b/ui/src/main_window.ui
@@ -298,6 +298,30 @@
           </property>
          </widget>
         </item>
+        <item>
+         <widget class="QLabel" name="label_2">
+          <property name="text">
+           <string>Use normal at</string>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QRadioButton" name="normalFromLight">
+          <property name="text">
+           <string>Hit position</string>
+          </property>
+          <property name="checked">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
+        <item>
+         <widget class="QRadioButton" name="normalFromCamera">
+          <property name="text">
+           <string>Show position</string>
+          </property>
+         </widget>
+        </item>
        </layout>
       </widget>
      </item>
@@ -637,8 +661,41 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>normalFromLight</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateViewIf(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1429</x>
+     <y>787</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>1381</x>
+     <y>783</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>normalFromCamera</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>MainWindow</receiver>
+   <slot>updateViewIf(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>1932</x>
+     <y>816</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>1600</x>
+     <y>874</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
  <slots>
   <slot>updateView()</slot>
+  <slot>updateViewIf(bool)</slot>
  </slots>
 </ui>