Document the direction that directional and spot lights emit light in

doc/classes/DirectionalLight2D.xml

@@ -5,6 +5,7 @@
 	</brief_description>
 	<description>
 		A directional light is a type of [Light2D] node that models an infinite number of parallel rays covering the entire scene. It is used for lights with strong intensity that are located far away from the scene (for example: to model sunlight or moonlight).
+		Light is emitted in the +Y direction of the node's global basis. For an unrotated light, this means that the light is emitted downwards. The position of the node is ignored; only the basis is used to determine light direction.
 		[b]Note:[/b] [DirectionalLight2D] does not support light cull masks (but it supports shadow cull masks). It will always light up 2D nodes, regardless of the 2D node's [member CanvasItem.light_mask].
 	</description>
 	<tutorials>

doc/classes/DirectionalLight3D.xml

@@ -4,7 +4,8 @@
 		Directional light from a distance, as from the Sun.
 	</brief_description>
 	<description>
-		A directional light is a type of [Light3D] node that models an infinite number of parallel rays covering the entire scene. It is used for lights with strong intensity that are located far away from the scene to model sunlight or moonlight. The worldspace location of the DirectionalLight3D transform (origin) is ignored. Only the basis is used to determine light direction.
+		A directional light is a type of [Light3D] node that models an infinite number of parallel rays covering the entire scene. It is used for lights with strong intensity that are located far away from the scene to model sunlight or moonlight.
+		Light is emitted in the -Z direction of the node's global basis. For an unrotated light, this means that the light is emitted forwards, illuminating the front side of a 3D model (see [constant Vector3.FORWARD] and [constant Vector3.MODEL_FRONT]). The position of the node is ignored; only the basis is used to determine light direction.
 	</description>
 	<tutorials>
 		<link title="3D lights and shadows">$DOCS_URL/tutorials/3d/lights_and_shadows.html</link>

doc/classes/SpotLight3D.xml

@@ -5,6 +5,7 @@
 	</brief_description>
 	<description>
 		A Spotlight is a type of [Light3D] node that emits lights in a specific direction, in the shape of a cone. The light is attenuated through the distance. This attenuation can be configured by changing the energy, radius and attenuation parameters of [Light3D].
+		Light is emitted in the -Z direction of the node's global basis. For an unrotated light, this means that the light is emitted forwards, illuminating the front side of a 3D model (see [constant Vector3.FORWARD] and [constant Vector3.MODEL_FRONT]).
 		[b]Note:[/b] When using the Mobile rendering method, only 8 spot lights can be displayed on each mesh resource. Attempting to display more than 8 spot lights on a single mesh resource will result in spot lights flickering in and out as the camera moves. When using the Compatibility rendering method, only 8 spot lights can be displayed on each mesh resource by default, but this can be increased by adjusting [member ProjectSettings.rendering/limits/opengl/max_lights_per_object].
 		[b]Note:[/b] When using the Mobile or Compatibility rendering methods, spot lights will only correctly affect meshes whose visibility AABB intersects with the light's AABB. If using a shader to deform the mesh in a way that makes it go outside its AABB, [member GeometryInstance3D.extra_cull_margin] must be increased on the mesh. Otherwise, the light may not be visible on the mesh.
 	</description>
@@ -18,7 +19,7 @@
 		<member name="shadow_bias" type="float" setter="set_param" getter="get_param" overrides="Light3D" default="0.03" />
 		<member name="shadow_normal_bias" type="float" setter="set_param" getter="get_param" overrides="Light3D" default="1.0" />
 		<member name="spot_angle" type="float" setter="set_param" getter="get_param" default="45.0">
-			The spotlight's angle in degrees.
+			The spotlight's angle in degrees. This is the angular radius, meaning the angle from the -Z axis, the cone's center, to the edge of the cone. The default angular radius of 45 degrees corresponds to a cone with an angular diameter of 90 degrees.
 			[b]Note:[/b] [member spot_angle] is not affected by [member Node3D.scale] (the light's scale or its parent's scale).
 		</member>
 		<member name="spot_angle_attenuation" type="float" setter="set_param" getter="get_param" default="1.0">