Improve angular radius calculation in astronomy system

src/ecs/systems/astronomy-system.cpp

@@ -189,8 +189,8 @@ void astronomy_system::update(double t, double dt)
 				this->sky_pass->set_sun_position(math::type_cast<float>(blackbody_position_topocentric));
 				this->sky_pass->set_sun_color(math::type_cast<float>(blackbody.color * blackbody_illuminance));
 				
-				float angular_radius = 2.0 * std::atan2(2.0 * blackbody.radius, 2.0 * blackbody_distance);
-				this->sky_pass->set_sun_angular_radius(angular_radius);
+				double blackbody_angular_radius = std::asin((blackbody.radius * 2.0) / (blackbody_distance * 2.0));
+				this->sky_pass->set_sun_angular_radius(static_cast<float>(blackbody_angular_radius));
 			}
 		}
 	});

src/physics/atmosphere.hpp

@@ -48,8 +48,8 @@ T density(T d0, T z, T sh)
 /**
  * Calculates a particle polarization factor used in computing scattering coefficients.
  *
- * @param ior Atmospheric index of refraction at sea level.
- * @param density Molecular density at sea level.
+ * @param ior Atmospheric index of refraction.
+ * @param density Molecular density.
  * @return Polarization factor.
  *
  * @see Elek, Oskar. (2009). Rendering Parametrizable Planetary Atmospheres with Multiple Scattering in Real-Time.

src/renderer/passes/sky-pass.cpp

@@ -234,8 +234,8 @@ void sky_pass::render(render_context* context) const
 			observer_altitude_input->upload(observer_altitude);
 		if (sun_direction_input)
 			sun_direction_input->upload(sun_direction);
-		if (cos_sun_angular_radius_input)
-			cos_sun_angular_radius_input->upload(cos_sun_angular_radius);
+		if (sun_angular_radius_input)
+			sun_angular_radius_input->upload(sun_angular_radius);
 		if (sun_color_input)
 			sun_color_input->upload(sun_color);
 		if (scale_height_rm_input)
@@ -347,7 +347,7 @@ void sky_pass::set_sky_model(const model* model)
 				observer_altitude_input = sky_shader_program->get_input("observer_altitude");
 				sun_direction_input = sky_shader_program->get_input("sun_direction");
 				sun_color_input = sky_shader_program->get_input("sun_color");
-				cos_sun_angular_radius_input = sky_shader_program->get_input("cos_sun_angular_radius");
+				sun_angular_radius_input = sky_shader_program->get_input("sun_angular_radius");
 				scale_height_rm_input = sky_shader_program->get_input("scale_height_rm");
 				rayleigh_scattering_input = sky_shader_program->get_input("rayleigh_scattering");
 				mie_scattering_input = sky_shader_program->get_input("mie_scattering");
@@ -430,7 +430,7 @@ void sky_pass::set_sun_color(const float3& color)
 
 void sky_pass::set_sun_angular_radius(float radius)
 {
-	cos_sun_angular_radius = std::cos(radius);
+	sun_angular_radius = radius;
 }
 
 void sky_pass::set_observer_altitude(float altitude)

src/renderer/passes/sky-pass.hpp

@@ -80,7 +80,7 @@ private:
 	const gl::shader_input* observer_altitude_input;
 	const gl::shader_input* sun_direction_input;
 	const gl::shader_input* sun_color_input;
-	const gl::shader_input* cos_sun_angular_radius_input;
+	const gl::shader_input* sun_angular_radius_input;
 	const gl::shader_input* scale_height_rm_input;
 	const gl::shader_input* rayleigh_scattering_input;
 	const gl::shader_input* mie_scattering_input;
@@ -128,7 +128,7 @@ private:
 	tween<float3> topocentric_frame_translation;
 	tween<math::quaternion<float>> topocentric_frame_rotation;
 	
-	float cos_sun_angular_radius;
+	float sun_angular_radius;
 	float2 scale_height_rm;
 	float3 rayleigh_scattering;
 	float3 mie_scattering;