Cao's optical illusions look so real that a parrot ended up pecking at peanuts he had painted. Not to mention visitors trying to pick up the Rubik's cube on his desk or friends feeling tricked when they realize the platter of fruits is, well, just paper.

For perspective, the artist often places a coin or a lipstick near his larger-than-life images. "Creating 3D paintings requires patience and practice. The basic principle is to trick the mind, which interprets signals our eyes send," says the 40-something artist.

"Once the mathematical rules are mastered, innovative experiments can be done," he adds.

Cao's paintings have packed in more than 5 million fans on the popular short video platform Douyin. Many of his works have garnered more than 1 million views each, with the highest reaching 5 million.

Some cheeky fans even request Cao to paint 3D girlfriends for them. "I sometimes oblige them because I see it more as a test of my skills than a compliment," he says.