manual/render/shader_nodes/shader/ray_portal.rst

@@ -15,6 +15,14 @@ render passes are passed through,
 and it is affected by light path max transparent bounces.
 
 
+.. note::
+
+   - The portal only allows rays to pass through in one direction.
+
+   - Some of the techniques Cycles uses to reduce noise does not work through portals.
+     This leads to issues like increased noise from lights passing through portals,
+     or if the light is small, it's light may not pass through the portal.
+
 Inputs
 ======