Ambient luminance threshold setting

apps/openmw/mwrender/renderingmanager.cpp

@@ -195,6 +195,7 @@ namespace MWRender
         , mWorkQueue(workQueue)
         , mUnrefQueue(new SceneUtil::UnrefQueue)
         , mNavigator(navigator)
+        , mMinimumAmbientLuminance(0.f)
         , mNightEyeFactor(0.f)
         , mFieldOfViewOverridden(false)
         , mFieldOfViewOverride(0.f)
@@ -223,6 +224,9 @@ namespace MWRender
         resourceSystem->getSceneManager()->getShaderManager().setLightingMethod(sceneRoot->getLightingMethod());
         resourceSystem->getSceneManager()->setLightingMethod(sceneRoot->getLightingMethod());
 
+        if (sceneRoot->getLightingMethod() != SceneUtil::LightingMethod::FFP)
+            mMinimumAmbientLuminance = std::clamp(Settings::Manager::getFloat("minimum interior brightness", "Shaders"), 0.f, 1.f);
+
         sceneRoot->setLightingMask(Mask_Lighting);
         mSceneRoot = sceneRoot;
         sceneRoot->setStartLight(1);
@@ -1072,7 +1076,25 @@ namespace MWRender
         osg::Vec4f color = mAmbientColor;
 
         if (mNightEyeFactor > 0.f)
+        {
             color += osg::Vec4f(0.7, 0.7, 0.7, 0.0) * mNightEyeFactor;
+        }
+        // optionally brighten up ambient interiors when using a non-FFP emulated lighting method
+        else if (mResourceSystem->getSceneManager()->getLightingMethod() != SceneUtil::LightingMethod::FFP)
+        {
+            static constexpr float pR = 0.2126;
+            static constexpr float pG = 0.7152;
+            static constexpr float pB = 0.0722;
+
+            // we already work in linear RGB so no conversions are needed for the luminosity function
+            float relativeLuminance = pR*color.r() + pG*color.g() + pB*color.b();
+            if (relativeLuminance < mMinimumAmbientLuminance)
+            {
+                // brighten ambient so it reaches the minimum threshold but no more, we want to mess with content data as least we can
+                float targetBrightnessIncreaseFactor = mMinimumAmbientLuminance / relativeLuminance;
+                color *= targetBrightnessIncreaseFactor;
+            }
+        }
 
         mStateUpdater->setAmbientColor(color);
     }

apps/openmw/mwrender/renderingmanager.hpp

@@ -296,6 +296,7 @@ namespace MWRender
         osg::ref_ptr<StateUpdater> mStateUpdater;
 
         osg::Vec4f mAmbientColor;
+        float mMinimumAmbientLuminance;
         float mNightEyeFactor;
 
         float mNearClip;

docs/source/reference/modding/settings/shaders.rst

@@ -238,6 +238,25 @@ lighting` is on.
 
 This setting has no effect if :ref:`lighting method` is 'legacy'.
 
+minimum interior brightness
+------------------------
+
+:Type:		float
+:Range:		0.0-1.0
+:Default:	0.1
+
+Sets the minimum interior ambient brightness for interior cells when
+:ref:`lighting method` is not 'legacy'. A consequence of the new lighting system
+is that interiors will sometimes be darker since light sources now have sensible
+fall-offs. A couple solutions are to either add more lights or increase their
+radii to compensate, but these require content changes. For best results it is
+recommended to set this to 0.0 to retain the colors that level designers
+intended. If brighter interiors are wanted, however, this setting should be
+increased. Note, it is advised to keep this number small (< 0.1) to avoid the
+aforementioned changes in visuals.
+
+This setting has no effect if :ref:`lighting method` is 'legacy'.
+
 antialias alpha test
 ---------------------------------------
 

files/settings-default.cfg

@@ -469,6 +469,11 @@ light fade start = 0.85
 # When 'lighting method' is set to 'legacy', this setting will have no effect.
 max lights = 8
 
+# Sets minimum ambient brightness of interior cells. Levels below this threshold will have their
+# ambient values adjusted to balance the darker interiors. 
+# When 'lighting method' is set to 'legacy', this setting will have no effect.
+minimum interior brightness = 0.1
+
 # Convert the alpha test (cutout/punchthrough alpha) to alpha-to-coverage.
 # This allows MSAA to work with alpha-tested meshes, producing better-looking edges without pixelation.
 # When MSAA is off, this setting will have no visible effect, but might have a performance cost.