Only show relevant properties in the DirectionalLight3D inspector

Some split distance properties are unused depending on the
current shadow mode. Also, Blend Splits can only be used if the shadow
mode is PSSM 2 Splits or PSSM 4 Splits.

This also moves the Fade Start property to be located after the
split properties. This avoids intertwining "conditional" properties
with a property that's always available.

3 files changed, 24 insertions, 15 deletions

diff --git a/doc/classes/DirectionalLight3D.xml b/doc/classes/DirectionalLight3D.xml
index f2a6e5b6f8..128c960138 100644
--- a/doc/classes/DirectionalLight3D.xml
+++ b/doc/classes/DirectionalLight3D.xml
@@ -11,10 +11,10 @@
 	</tutorials>
 	<members>
 		<member name="directional_shadow_blend_splits" type="bool" setter="set_blend_splits" getter="is_blend_splits_enabled" default="false">
-			If [code]true[/code], shadow detail is sacrificed in exchange for smoother transitions between splits. This is ignored when [member directional_shadow_mode] is [code]SHADOW_ORTHOGONAL[/code].
+			If [code]true[/code], shadow detail is sacrificed in exchange for smoother transitions between splits. Enabling shadow blend splitting also has a moderate performance cost. This is ignored when [member directional_shadow_mode] is [code]SHADOW_ORTHOGONAL[/code].
 		</member>
 		<member name="directional_shadow_fade_start" type="float" setter="set_param" getter="get_param" default="0.8">
-			Proportion of [member directional_shadow_max_distance] at which point the shadow starts to fade. At [member directional_shadow_max_distance] the shadow will disappear.
+			Proportion of [member directional_shadow_max_distance] at which point the shadow starts to fade. At [member directional_shadow_max_distance], the shadow will disappear. The default value is a balance between smooth fading and distant shadow visibility. If the camera moves fast and the [member directional_shadow_max_distance] is low, consider lowering [member directional_shadow_fade_start] below [code]0.8[/code] to make shadow transitions less noticeable. On the other hand, if you tuned [member directional_shadow_max_distance] to cover the entire scene, you can set [member directional_shadow_fade_start] to [code]1.0[/code] to prevent the shadow from fading in the distance (it will suddenly cut off instead).
 		</member>
 		<member name="directional_shadow_max_distance" type="float" setter="set_param" getter="get_param" default="100.0">
 			The maximum distance for shadow splits.
diff --git a/scene/3d/light_3d.cpp b/scene/3d/light_3d.cpp
index c787ba5087..c4b58cefaf 100644
--- a/scene/3d/light_3d.cpp
+++ b/scene/3d/light_3d.cpp
@@ -200,19 +200,8 @@ void Light3D::_validate_property(PropertyInfo &property) const {
 		property.usage = PROPERTY_USAGE_NOEDITOR;
 	}
 
-	if (get_light_type() == RS::LIGHT_DIRECTIONAL && property.name == "light_size") {
-		property.usage = PROPERTY_USAGE_NONE;
-	}
-
-	if (get_light_type() == RS::LIGHT_DIRECTIONAL && property.name == "light_specular") {
-		property.usage = PROPERTY_USAGE_NONE;
-	}
-
-	if (get_light_type() == RS::LIGHT_DIRECTIONAL && property.name == "light_projector") {
-		property.usage = PROPERTY_USAGE_NONE;
-	}
-
 	if (get_light_type() != RS::LIGHT_DIRECTIONAL && property.name == "light_angular_distance") {
+		// Angular distance is only used in DirectionalLight3D.
 		property.usage = PROPERTY_USAGE_NONE;
 	}
 }
@@ -361,6 +350,7 @@ Light3D::~Light3D() {
 void DirectionalLight3D::set_shadow_mode(ShadowMode p_mode) {
 	shadow_mode = p_mode;
 	RS::get_singleton()->light_directional_set_shadow_mode(light, RS::LightDirectionalShadowMode(p_mode));
+	notify_property_list_changed();
 }
 
 DirectionalLight3D::ShadowMode DirectionalLight3D::get_shadow_mode() const {
@@ -370,6 +360,7 @@ DirectionalLight3D::ShadowMode DirectionalLight3D::get_shadow_mode() const {
 void DirectionalLight3D::set_blend_splits(bool p_enable) {
 	blend_splits = p_enable;
 	RS::get_singleton()->light_directional_set_blend_splits(light, p_enable);
+	notify_property_list_changed();
 }
 
 bool DirectionalLight3D::is_blend_splits_enabled() const {
@@ -385,6 +376,23 @@ bool DirectionalLight3D::is_sky_only() const {
 	return sky_only;
 }
 
+void DirectionalLight3D::_validate_property(PropertyInfo &property) const {
+	if (shadow_mode == SHADOW_ORTHOGONAL && (property.name == "directional_shadow_split_1" || property.name == "directional_shadow_blend_splits")) {
+		// Split 2 and split blending are only used with PSSM 2 Splits and PSSM 4 Splits shadow mode.
+		property.usage = PROPERTY_USAGE_NOEDITOR;
+	}
+
+	if ((shadow_mode == SHADOW_ORTHOGONAL || shadow_mode == SHADOW_PARALLEL_2_SPLITS) && (property.name == "directional_shadow_split_2" || property.name == "directional_shadow_split_3")) {
+		// Splits 3 and 4 are only used with PSSM 4 Splits shadow mode.
+		property.usage = PROPERTY_USAGE_NOEDITOR;
+	}
+
+	if (property.name == "light_size" || property.name == "light_projector" || property.name == "light_specular") {
+		// Not implemented in DirectionalLight3D (`light_size` is replaced by `light_angular_distance`).
+		property.usage = PROPERTY_USAGE_NONE;
+	}
+}
+
 void DirectionalLight3D::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_shadow_mode", "mode"), &DirectionalLight3D::set_shadow_mode);
 	ClassDB::bind_method(D_METHOD("get_shadow_mode"), &DirectionalLight3D::get_shadow_mode);
@@ -400,8 +408,8 @@ void DirectionalLight3D::_bind_methods() {
 	ADD_PROPERTYI(PropertyInfo(Variant::FLOAT, "directional_shadow_split_1", PROPERTY_HINT_RANGE, "0,1,0.001"), "set_param", "get_param", PARAM_SHADOW_SPLIT_1_OFFSET);
 	ADD_PROPERTYI(PropertyInfo(Variant::FLOAT, "directional_shadow_split_2", PROPERTY_HINT_RANGE, "0,1,0.001"), "set_param", "get_param", PARAM_SHADOW_SPLIT_2_OFFSET);
 	ADD_PROPERTYI(PropertyInfo(Variant::FLOAT, "directional_shadow_split_3", PROPERTY_HINT_RANGE, "0,1,0.001"), "set_param", "get_param", PARAM_SHADOW_SPLIT_3_OFFSET);
-	ADD_PROPERTYI(PropertyInfo(Variant::FLOAT, "directional_shadow_fade_start", PROPERTY_HINT_RANGE, "0,1,0.01"), "set_param", "get_param", PARAM_SHADOW_FADE_START);
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "directional_shadow_blend_splits"), "set_blend_splits", "is_blend_splits_enabled");
+	ADD_PROPERTYI(PropertyInfo(Variant::FLOAT, "directional_shadow_fade_start", PROPERTY_HINT_RANGE, "0,1,0.01"), "set_param", "get_param", PARAM_SHADOW_FADE_START);
 	ADD_PROPERTYI(PropertyInfo(Variant::FLOAT, "directional_shadow_max_distance", PROPERTY_HINT_RANGE, "0,8192,0.1,or_greater,exp"), "set_param", "get_param", PARAM_SHADOW_MAX_DISTANCE);
 	ADD_PROPERTYI(PropertyInfo(Variant::FLOAT, "directional_shadow_pancake_size", PROPERTY_HINT_RANGE, "0,1024,0.1,or_greater,exp"), "set_param", "get_param", PARAM_SHADOW_PANCAKE_SIZE);
 
diff --git a/scene/3d/light_3d.h b/scene/3d/light_3d.h
index f788c323f7..a9f5ce27b4 100644
--- a/scene/3d/light_3d.h
+++ b/scene/3d/light_3d.h
@@ -152,6 +152,7 @@ private:
 
 protected:
 	static void _bind_methods();
+	virtual void _validate_property(PropertyInfo &property) const override;
 
 public:
 	void set_shadow_mode(ShadowMode p_mode);