Add Environment properties to control fog rendering on background sky

Values lower than 1.0 can be used to make the fog rendering not fully
obstruct the sky. This can be desired when using fog as a purely
atmospheric effect, without intending to use fog for open world fog
fading.

When set to 0.0, fog rendering behavior will be similar to Godot 3.x
where sky rendering was never affected by fog.

2 files changed, 48 insertions, 2 deletions

diff --git a/scene/resources/environment.cpp b/scene/resources/environment.cpp
index f7a7818b3b..5e5d2c4fa4 100644
--- a/scene/resources/environment.cpp
+++ b/scene/resources/environment.cpp
@@ -852,6 +852,15 @@ float Environment::get_fog_aerial_perspective() const {
 	return fog_aerial_perspective;
 }
 
+void Environment::set_fog_sky_affect(float p_sky_affect) {
+	fog_sky_affect = p_sky_affect;
+	_update_fog();
+}
+
+float Environment::get_fog_sky_affect() const {
+	return fog_sky_affect;
+}
+
 void Environment::_update_fog() {
 	RS::get_singleton()->environment_set_fog(
 			environment,
@@ -862,13 +871,28 @@ void Environment::_update_fog() {
 			fog_density,
 			fog_height,
 			fog_height_density,
-			fog_aerial_perspective);
+			fog_aerial_perspective,
+			fog_sky_affect);
 }
 
 // Volumetric Fog
 
 void Environment::_update_volumetric_fog() {
-	RS::get_singleton()->environment_set_volumetric_fog(environment, volumetric_fog_enabled, volumetric_fog_density, volumetric_fog_albedo, volumetric_fog_emission, volumetric_fog_emission_energy, volumetric_fog_anisotropy, volumetric_fog_length, volumetric_fog_detail_spread, volumetric_fog_gi_inject, volumetric_fog_temporal_reproject, volumetric_fog_temporal_reproject_amount, volumetric_fog_ambient_inject);
+	RS::get_singleton()->environment_set_volumetric_fog(
+			environment,
+			volumetric_fog_enabled,
+			volumetric_fog_density,
+			volumetric_fog_albedo,
+			volumetric_fog_emission,
+			volumetric_fog_emission_energy,
+			volumetric_fog_anisotropy,
+			volumetric_fog_length,
+			volumetric_fog_detail_spread,
+			volumetric_fog_gi_inject,
+			volumetric_fog_temporal_reproject,
+			volumetric_fog_temporal_reproject_amount,
+			volumetric_fog_ambient_inject,
+			volumetric_fog_sky_affect);
 }
 
 void Environment::set_volumetric_fog_enabled(bool p_enable) {
@@ -946,6 +970,15 @@ float Environment::get_volumetric_fog_ambient_inject() const {
 	return volumetric_fog_ambient_inject;
 }
 
+void Environment::set_volumetric_fog_sky_affect(float p_sky_affect) {
+	volumetric_fog_sky_affect = p_sky_affect;
+	_update_volumetric_fog();
+}
+
+float Environment::get_volumetric_fog_sky_affect() const {
+	return volumetric_fog_sky_affect;
+}
+
 void Environment::set_volumetric_fog_temporal_reprojection_enabled(bool p_enable) {
 	volumetric_fog_temporal_reproject = p_enable;
 	_update_volumetric_fog();
@@ -1419,6 +1452,9 @@ void Environment::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_fog_aerial_perspective", "aerial_perspective"), &Environment::set_fog_aerial_perspective);
 	ClassDB::bind_method(D_METHOD("get_fog_aerial_perspective"), &Environment::get_fog_aerial_perspective);
 
+	ClassDB::bind_method(D_METHOD("set_fog_sky_affect", "sky_affect"), &Environment::set_fog_sky_affect);
+	ClassDB::bind_method(D_METHOD("get_fog_sky_affect"), &Environment::get_fog_sky_affect);
+
 	ADD_GROUP("Fog", "fog_");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "fog_enabled"), "set_fog_enabled", "is_fog_enabled");
 	ADD_PROPERTY(PropertyInfo(Variant::COLOR, "fog_light_color", PROPERTY_HINT_COLOR_NO_ALPHA), "set_fog_light_color", "get_fog_light_color");
@@ -1427,6 +1463,7 @@ void Environment::_bind_methods() {
 
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "fog_density", PROPERTY_HINT_RANGE, "0,1,0.0001,or_greater"), "set_fog_density", "get_fog_density");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "fog_aerial_perspective", PROPERTY_HINT_RANGE, "0,1,0.001"), "set_fog_aerial_perspective", "get_fog_aerial_perspective");
+	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "fog_sky_affect", PROPERTY_HINT_RANGE, "0,1,0.001"), "set_fog_sky_affect", "get_fog_sky_affect");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "fog_height", PROPERTY_HINT_RANGE, "-1024,1024,0.01,or_lesser,or_greater,suffix:m"), "set_fog_height", "get_fog_height");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "fog_height_density", PROPERTY_HINT_RANGE, "-16,16,0.0001,or_lesser,or_greater"), "set_fog_height_density", "get_fog_height_density");
 
@@ -1450,6 +1487,8 @@ void Environment::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_volumetric_fog_gi_inject"), &Environment::get_volumetric_fog_gi_inject);
 	ClassDB::bind_method(D_METHOD("set_volumetric_fog_ambient_inject", "enabled"), &Environment::set_volumetric_fog_ambient_inject);
 	ClassDB::bind_method(D_METHOD("get_volumetric_fog_ambient_inject"), &Environment::get_volumetric_fog_ambient_inject);
+	ClassDB::bind_method(D_METHOD("set_volumetric_fog_sky_affect", "sky_affect"), &Environment::set_volumetric_fog_sky_affect);
+	ClassDB::bind_method(D_METHOD("get_volumetric_fog_sky_affect"), &Environment::get_volumetric_fog_sky_affect);
 	ClassDB::bind_method(D_METHOD("set_volumetric_fog_temporal_reprojection_enabled", "enabled"), &Environment::set_volumetric_fog_temporal_reprojection_enabled);
 	ClassDB::bind_method(D_METHOD("is_volumetric_fog_temporal_reprojection_enabled"), &Environment::is_volumetric_fog_temporal_reprojection_enabled);
 	ClassDB::bind_method(D_METHOD("set_volumetric_fog_temporal_reprojection_amount", "temporal_reprojection_amount"), &Environment::set_volumetric_fog_temporal_reprojection_amount);
@@ -1466,6 +1505,7 @@ void Environment::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "volumetric_fog_length", PROPERTY_HINT_RANGE, "0,1024,0.01,or_greater"), "set_volumetric_fog_length", "get_volumetric_fog_length");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "volumetric_fog_detail_spread", PROPERTY_HINT_EXP_EASING, "positive_only"), "set_volumetric_fog_detail_spread", "get_volumetric_fog_detail_spread");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "volumetric_fog_ambient_inject", PROPERTY_HINT_RANGE, "0.0,16,0.01,exp"), "set_volumetric_fog_ambient_inject", "get_volumetric_fog_ambient_inject");
+	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "volumetric_fog_sky_affect", PROPERTY_HINT_RANGE, "0,1,0.001"), "set_volumetric_fog_sky_affect", "get_volumetric_fog_sky_affect");
 	ADD_SUBGROUP("Temporal Reprojection", "volumetric_fog_temporal_reprojection_");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "volumetric_fog_temporal_reprojection_enabled"), "set_volumetric_fog_temporal_reprojection_enabled", "is_volumetric_fog_temporal_reprojection_enabled");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "volumetric_fog_temporal_reprojection_amount", PROPERTY_HINT_RANGE, "0.5,0.99,0.001"), "set_volumetric_fog_temporal_reprojection_amount", "get_volumetric_fog_temporal_reprojection_amount");
diff --git a/scene/resources/environment.h b/scene/resources/environment.h
index d39cb1acd8..0b8e8c38d7 100644
--- a/scene/resources/environment.h
+++ b/scene/resources/environment.h
@@ -182,6 +182,7 @@ private:
 	float fog_height = 0.0;
 	float fog_height_density = 0.0; //can be negative to invert effect
 	float fog_aerial_perspective = 0.0;
+	float fog_sky_affect = 1.0;
 
 	void _update_fog();
 
@@ -196,6 +197,7 @@ private:
 	float volumetric_fog_detail_spread = 2.0;
 	float volumetric_fog_gi_inject = 1.0;
 	float volumetric_fog_ambient_inject = 0.0;
+	float volumetric_fog_sky_affect = 1.0;
 	bool volumetric_fog_temporal_reproject = true;
 	float volumetric_fog_temporal_reproject_amount = 0.9;
 	void _update_volumetric_fog();
@@ -385,6 +387,8 @@ public:
 	float get_fog_height_density() const;
 	void set_fog_aerial_perspective(float p_aerial_perspective);
 	float get_fog_aerial_perspective() const;
+	void set_fog_sky_affect(float p_sky_affect);
+	float get_fog_sky_affect() const;
 
 	// Volumetric Fog
 	void set_volumetric_fog_enabled(bool p_enable);
@@ -407,6 +411,8 @@ public:
 	float get_volumetric_fog_gi_inject() const;
 	void set_volumetric_fog_ambient_inject(float p_ambient_inject);
 	float get_volumetric_fog_ambient_inject() const;
+	void set_volumetric_fog_sky_affect(float p_sky_affect);
+	float get_volumetric_fog_sky_affect() const;
 	void set_volumetric_fog_temporal_reprojection_enabled(bool p_enable);
 	bool is_volumetric_fog_temporal_reprojection_enabled() const;
 	void set_volumetric_fog_temporal_reprojection_amount(float p_amount);