During the day, when outdoor light is generally brighter than indoor light, the light reflected from outdoor is much stronger
During the day, when outdoor light is generally brighter than indoor light, the light reflected from outdoor is much stronger than the faint light transmitted from indoor. When you look at the room from the outside through the curtains, the reflection of indoor objects is blurred. When the light meets certain conditions, the indoor objects are invisible.
It's like we can't see fireflies under the strong light of street lamps, because the faint light emitted by fireflies is drowned by the light of street lamps.
On the contrary, when you look out from indoors, the images reflected by outdoor objects are clearer.
One-way perspective function is thus formed.