moricecorpsoft3

Properties of "ViewPort" to change:

Warning:
The Camera might be child of ViewPort (Put the Camera like child of a "Spatial" and this "Spatial" like child of "ViewPort");
Set Position and Rotation of Camera like you wish for.

Properties to change:
Size x = 100
Size y = 100

Rendering:
Msaa = 8x (Hint: Only to have better image of mirror)

Render Target:
V Flip = On -> checked
Clear Mode = Always
Update Mode = Always

Script:
Viewport.gd -> This file contains inside of the project.