Greetings everyone !!
Optical illusion triangle :
The process :
1.Draw an L .
2 . Make it 3D.
3 . Draw 3 parallel lines from the top edge of the L.
4 . Erase a few lines .
5 . Shade the lower area darker and the other one lighter.
Have a great day !
Learned it from the youtube channel : Art of wei .