fix(Volumetric Shadows): Interior Sun Compatibility

package/Shaders/Common/SharedData.hlsli

@@ -267,6 +267,13 @@ namespace SharedData
 		float3 pad;
 	};
 
+	struct InteriorSunSettings
+	{
+		float EffectMeshSunInfluence;
+		uint IsInteriorWithSun;
+		float2 pad0;
+	};
+
 	cbuffer FeatureData : register(b6)
 	{
 		GrassLightingSettings grassLightingSettings;
@@ -285,6 +292,7 @@ namespace SharedData
 		LinearLightingSettings linearLightingSettings;
 		TerrainBlendingSettings terrainBlendingSettings;
 		ExponentialHeightFogSettings exponentialHeightFogSettings;
+		InteriorSunSettings interiorSunSettings;
 	};
 
 	Texture2D<float4> DepthTexture : register(t17);

package/Shaders/Effect.hlsl

@@ -562,13 +562,15 @@ float3 GetLightingColor(float3 msPosition, float3 worldPosition, float2 screenPo
 	float dirShadow = 1.0;
 
 	const bool inWorld = (Permutation::ExtraShaderDescriptor & Permutation::ExtraFlags::InWorld);
+	const bool isInteriorSun = SharedData::interiorSunSettings.IsInteriorWithSun;
 
-	if (inWorld && !SharedData::InInterior)
+	if (inWorld && (!SharedData::InInterior || isInteriorSun))
 		dirShadow = ShadowSampling::Get3DFilteredShadow(worldPosition.xyz, viewDirection, screenPosition, eyeIndex, unusedSurfaceShadow);
 
 	shadowVariance = 1.0 - sqrt(saturate(fwidth(dirShadow)));
 
-	dirColor *= dirShadow;
+	if (!isInteriorSun)
+		dirColor *= dirShadow;
 
 #		if defined(EXP_HEIGHT_FOG)
 	if (SharedData::exponentialHeightFogSettings.enabled) {
@@ -584,6 +586,11 @@ float3 GetLightingColor(float3 msPosition, float3 worldPosition, float2 screenPo
 
 	color = dirColor + ambientColor;
 
+	if (isInteriorSun) {
+		float influence = SharedData::interiorSunSettings.EffectMeshSunInfluence;
+		color *= lerp(1.0, dirShadow, influence);
+	}
+
 #		if defined(LIGHT_LIMIT_FIX)
 	if (!(Permutation::ExtraShaderDescriptor & Permutation::ExtraFlags::InWorld))
 #		endif
@@ -628,6 +635,7 @@ float3 GetLightingShadow(float3 color, float3 worldPosition, float2 screenPositi
 	float shadow = 1.0;
 
 	const bool inWorld = (Permutation::ExtraShaderDescriptor & Permutation::ExtraFlags::InWorld);
+	const bool isInteriorSun = SharedData::interiorSunSettings.IsInteriorWithSun;
 
 	if (inWorld && !SharedData::InInterior) {
 		shadow = 0.0;
@@ -637,19 +645,30 @@ float3 GetLightingShadow(float3 color, float3 worldPosition, float2 screenPositi
 			shadow += ShadowSampling::GetWorldShadow(samplePositionWS, FrameBuffer::CameraPosAdjust[eyeIndex].xyz, eyeIndex);
 		}
 		shadow *= rcpSampleCount;
+	} else if (inWorld && isInteriorSun) {
+		float unusedSurfaceShadow;
+		shadow = ShadowSampling::Get3DFilteredShadow(worldPosition, viewDirection, screenPosition, eyeIndex, unusedSurfaceShadow);
 	}
 
 	shadowVariance = 1.0 - sqrt(saturate(fwidth(shadow)));
 
-	dirColor *= shadow;
+	if (!isInteriorSun)
+		dirColor *= shadow;
 
 #		if defined(EXP_HEIGHT_FOG)
 	if (SharedData::exponentialHeightFogSettings.enabled) {
 		dirColor *= ExponentialHeightFog::GetSunlightFogAttenuation(worldPosition.xyz, FrameBuffer::CameraPosAdjust[eyeIndex].xyz);
 	}
 #		endif
 
-	return dirColor + ambientColor;
+	color = dirColor + ambientColor;
+
+	if (isInteriorSun) {
+		float influence = SharedData::interiorSunSettings.EffectMeshSunInfluence;
+		color *= lerp(1.0, shadow, influence);
+	}
+
+	return color;
 }
 #	endif
 

package/Shaders/ISVolumetricLightingGenerateCS.hlsl

@@ -86,7 +86,7 @@ cbuffer PerTechnique : register(b0)
 
 	float shadowMapDepth = positionCSShifted.z;
 
-	bool noShadow = !SharedData::InInterior;
+	bool noShadow = !SharedData::InInterior || SharedData::interiorSunSettings.IsInteriorWithSun;
 	if (EndSplitDistances.z >= shadowMapDepth) {
 		uint cascadeIndex = ShadowMapCount >= 3.0f && shadowMapDepth > EndSplitDistances.y ? 2 : shadowMapDepth > EndSplitDistances.x ? 1 :
 		                                                                                                                                0;

package/Shaders/Lighting.hlsl

@@ -2496,7 +2496,7 @@ PS_OUTPUT main(PS_INPUT input, bool frontFace : SV_IsFrontFace)
 	float dirVSMDetailedShadow = 1.0;
 
 #	if defined(VOLUMETRIC_SHADOWS)
-	if (inWorld && !inReflection && !SharedData::InInterior)
+	if (inWorld && !inReflection)
 		dirSoftShadow = ShadowSampling::GetLightingShadow(input.WorldPosition.xyz, eyeIndex, dirVSMDetailedShadow);
 #	endif
 

package/Shaders/RunGrass.hlsl

@@ -597,8 +597,14 @@ PS_OUTPUT main(PS_INPUT input, bool frontFace : SV_IsFrontFace)
 	float4 shadowColor = TexShadowMaskSampler.Load(int3(input.HPosition.xy, 0));
 
 	// Apply world shadow (terrain shadows, cloud shadows) directly to light color
-	if (!SharedData::InInterior)
-		dirLightColor *= ShadowSampling::GetWorldShadow(input.WorldPosition.xyz, FrameBuffer::CameraPosAdjust[eyeIndex].xyz, eyeIndex);
+	dirLightColor *= ShadowSampling::GetWorldShadow(input.WorldPosition.xyz, FrameBuffer::CameraPosAdjust[eyeIndex].xyz, eyeIndex);
+
+	float dirSoftShadow = 1.0;
+	float dirVSMDetailedShadow = 1.0;
+
+#			if defined(VOLUMETRIC_SHADOWS)
+	dirSoftShadow = ShadowSampling::GetLightingShadow(input.WorldPosition.xyz, eyeIndex, dirVSMDetailedShadow);
+#			endif
 
 	float dirDetailedShadow = 1.0;
 
@@ -832,8 +838,7 @@ PS_OUTPUT main(PS_INPUT input)
 	float3 dirLightColor = Color::DirectionalLight(SharedData::DirLightColor.xyz / max(llDirLightMult, 1e-5), SharedData::linearLightingSettings.isDirLightLinear) * llDirLightMult;
 
 	// Apply world shadow (terrain shadows, cloud shadows) directly to light color
-	if (!SharedData::InInterior)
-		dirLightColor *= ShadowSampling::GetWorldShadow(input.WorldPosition.xyz, FrameBuffer::CameraPosAdjust[eyeIndex].xyz, eyeIndex);
+	dirLightColor *= ShadowSampling::GetWorldShadow(input.WorldPosition.xyz, FrameBuffer::CameraPosAdjust[eyeIndex].xyz, eyeIndex);
 
 	float dirDetailedShadow = 1.0;
 

src/FeatureBuffer.cpp

@@ -8,6 +8,7 @@
 #include "Features/GrassLighting.h"
 #include "Features/HairSpecular.h"
 #include "Features/IBL.h"
+#include "Features/InteriorSun.h"
 #include "Features/LODBlending.h"
 #include "Features/LightLimitFix.h"
 #include "Features/LinearLighting.h"
@@ -51,5 +52,6 @@ std::pair<unsigned char*, size_t> GetFeatureBufferData(bool a_inWorld)
 		globals::features::extendedTranslucency.GetCommonBufferData(),
 		globals::features::linearLighting.GetCommonBufferData(),
 		globals::features::terrainBlending.settings,
-		globals::features::exponentialHeightFog.settings);
+		globals::features::exponentialHeightFog.settings,
+		globals::features::interiorSun.GetShaderSettings());
 }

src/Features/InteriorSun.cpp

@@ -6,7 +6,8 @@
 NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(
 	InteriorSun::Settings,
 	ForceDoubleSidedRendering,
-	InteriorShadowDistance)
+	InteriorShadowDistance,
+	EffectMeshSunInfluence)
 
 void InteriorSun::DrawSettings()
 {
@@ -26,6 +27,13 @@ void InteriorSun::DrawSettings()
 			"Sets the distance shadows are rendered at in interiors. "
 			"Lower values provide higher quality shadows and improved performance but may cause distant interior spaces to light up incorrectly. ");
 	}
+	ImGui::SliderFloat("Effect Mesh Sun Influence", &settings.EffectMeshSunInfluence, 0.0f, 100.0f, "%.0f%%", ImGuiSliderFlags_AlwaysClamp);
+	if (auto _tt = Util::HoverTooltipWrapper()) {
+		ImGui::Text(
+			"Controls how much sunlight and shadows affect effect meshes (particles, fires, etc.) in interiors. "
+			"At 100%%, effect meshes receive full sun shadow darkening. "
+			"At 0%%, effect meshes ignore sunlight entirely, matching vanilla interior behavior. ");
+	}
 }
 
 void InteriorSun::LoadSettings(json& o_json)
@@ -216,6 +224,14 @@ bool InteriorSun::IsInSunDirectionAndWithinShadowDistance(const RE::NiPointer<RE
 	return projection >= -radius && (distance - radius) <= *gShadowDistance;
 }
 
+InteriorSun::ShaderSettings InteriorSun::GetShaderSettings() const
+{
+	ShaderSettings data;
+	data.EffectMeshSunInfluence = std::clamp(settings.EffectMeshSunInfluence, 0.0f, 100.0f) * 0.01f;
+	data.IsInteriorWithSun = isInteriorWithSun ? 1u : 0u;
+	return data;
+}
+
 void InteriorSun::SetShadowDistance(bool inInterior)
 {
 	using func_t = decltype(SetShadowDistance);

src/Features/InteriorSun.h

@@ -37,10 +37,21 @@ struct InteriorSun : Feature
 	{
 		bool ForceDoubleSidedRendering = true;
 		float InteriorShadowDistance = 5000;
+		float EffectMeshSunInfluence = 100.0f;
 	};
 
 	Settings settings;
 
+	struct alignas(16) ShaderSettings
+	{
+		float EffectMeshSunInfluence = 1.0f;
+		uint32_t IsInteriorWithSun = 0;
+		float pad[2] = {};
+	};
+	STATIC_ASSERT_ALIGNAS_16(ShaderSettings);
+
+	ShaderSettings GetShaderSettings() const;
+
 	std::atomic<bool> isInteriorWithSun = false;
 
 	struct GetWorldSpace