Keep sun irradiance constant when changing distance and size�

Author: mororo250

sandbox/settings/appleseed.studio.xml

@@ -10,19 +10,6 @@
         <parameter name="tile_ordering" value="spiral" />
     </parameters>
     <parameters name="ui">
-        <parameters name="file_dialog">
-            <parameters name="frames">
-                <parameter name="last_directory" value="D:\appleseed-scenes" />
-                <parameter name="selected_filter" value="JPEG Files (*.jpg *.jpe *.jpeg *.jif *.jfif *.jfi)" />
-            </parameters>
-            <parameters name="light_paths">
-                <parameter name="selected_filter" value="" />
-            </parameters>
-            <parameters name="projects">
-                <parameter name="last_directory" value="D:\appleseed\sandbox\tests\test scenes\light importance multipliers" />
-                <parameter name="selected_filter" value="Project Files (*.appleseed *.appleseedz)" />
-            </parameters>
-        </parameters>
         <parameters name="render_region">
             <parameter name="triggers_rendering" value="true" />
         </parameters>

src/appleseed/renderer/modeling/light/sunlight.cpp

@@ -146,6 +146,9 @@ bool SunLight::on_frame_begin(
         m_values.m_size_multiplier = 1.0f;
     }
 
+    // Keep sun's irradiance constant for different sizes and distances.
+    m_values.m_radiance_multiplier = 1.0f / m_values.m_size_multiplier * m_values.m_distance / 149.6f;
+
     // Compute the Sun's solid angle.
     // Reference: https://en.wikipedia.org/wiki/Solid_angle#Sun_and_Moon
     m_sun_solid_angle = TwoPi<float>() * (1.0f - std::cos(std::atan(SunRadius * m_values.m_size_multiplier / m_values.m_distance)));
@@ -566,7 +569,7 @@ void SunLight::sample_sun_surface(
 
     outgoing = normalize(target_point - position);
     Vector2d test = static_cast<double>(SunRadius * m_values.m_size_multiplier) * p;
-    float squared_distance_to_center = test[0] * test[0] + test[1] * test[1];
+    double squared_distance_to_center = test[0] * test[0] + test[1] * test[1];
 
 
     RegularSpectrum31f radiance;
@@ -575,7 +578,7 @@ void SunLight::sample_sun_surface(
         m_values.m_turbidity,
         m_values.m_radiance_multiplier,
         radiance,
-        squared_distance_to_center);
+        static_cast<float>(squared_distance_to_center));
 
     value.set(radiance, g_std_lighting_conditions, Spectrum::Illuminance);