Improve documentation related to anisotropic filtering

doc/classes/ProjectSettings.xml

@@ -1660,7 +1660,9 @@
 			[b]Note:[/b] The two video drivers are not drop-in replacements for each other, so a game designed for GLES3 might not work properly when falling back to GLES2. In particular, some features of the GLES3 backend are not available in GLES2. Enabling this setting also means that both ETC and ETC2 VRAM-compressed textures will be exported on Android and iOS, increasing the data pack's size.
 		</member>
 		<member name="rendering/quality/filters/anisotropic_filter_level" type="int" setter="" getter="" default="4">
-			Maximum anisotropic filter level used for textures with anisotropy enabled. Higher values will result in sharper textures when viewed from oblique angles, at the cost of performance. Only power-of-two values are valid (2, 4, 8, 16).
+			Maximum anisotropic filter level used for textures with anisotropy enabled. Higher values will result in sharper textures when viewed from oblique angles, at the cost of performance. With the exception of [code]1[/code], only power-of-two values are valid ([code]2[/code], [code]4[/code], [code]8[/code], [code]16[/code]). A value of [code]1[/code] forcibly disables anisotropic filtering, even on textures where it is enabled.
+			[b]Note:[/b] For performance reasons, anisotropic filtering [i]is not enabled by default[/i] on textures. For this setting to have an effect, anisotropic texture filtering can be enabled by selecting a texture in the FileSystem dock, going to the Import dock, checking the [b]Anisotropic[/b] checkbox then clicking [b]Reimport[/b]. However, anisotropic filtering is rarely useful in 2D, so only enable it for textures in 2D if it makes a meaningful visual difference.
+			[b]Note:[/b] This property is only read when the project starts. There is currently no way to change this setting at run-time.
 		</member>
 		<member name="rendering/quality/filters/msaa" type="int" setter="" getter="" default="0">
 			Sets the number of MSAA samples to use. MSAA is used to reduce aliasing around the edges of polygons. A higher MSAA value results in smoother edges but can be significantly slower on some hardware.

doc/classes/SpatialMaterial.xml

@@ -69,7 +69,7 @@
 		<member name="anisotropy_enabled" type="bool" setter="set_feature" getter="get_feature" default="false">
 			If [code]true[/code], anisotropy is enabled. Anisotropy changes the shape of the specular blob and aligns it to tangent space. This is useful for brushed aluminium and hair reflections.
 			[b]Note:[/b] Mesh tangents are needed for anisotropy to work. If the mesh does not contain tangents, the anisotropy effect will appear broken.
-			[b]Note:[/b] Material anisotropy should not to be confused with anisotropic texture filtering. Anisotropic texture filtering can be enabled by selecting a texture in the FileSystem dock, going to the Import dock, checking the [b]Anisotropic[/b] checkbox then clicking [b]Reimport[/b].
+			[b]Note:[/b] Material anisotropy should not to be confused with anisotropic texture filtering. Anisotropic texture filtering can be enabled by selecting a texture in the FileSystem dock, going to the Import dock, checking the [b]Anisotropic[/b] checkbox then clicking [b]Reimport[/b]. The anisotropic filtering level can be changed by adjusting [member ProjectSettings.rendering/quality/filters/anisotropic_filter_level].
 		</member>
 		<member name="anisotropy_flowmap" type="Texture" setter="set_texture" getter="get_texture">
 			Texture that offsets the tangent map for anisotropy calculations and optionally controls the anisotropy effect (if an alpha channel is present). The flowmap texture is expected to be a derivative map, with the red channel representing distortion on the X axis and green channel representing distortion on the Y axis. Values below 0.5 will result in negative distortion, whereas values above 0.5 will result in positive distortion.