How to use a ViewportFrame to replicate a player in the 3D world

A game called Blox Fruits has a skill that makes you able to see everyone through walls, and this is how it looks like:

I’m not 100% sure it uses a ViewportFrame but by the Lighting on the character compared to the lighting of the 3D world, it looks like that’s what they used. How would I replicate that?

This looks like it was more likely done with a selection box.

A selection box? Doesn’t that just render a box around a part? How would you use that to make the player not be affected by lighting

I was able to do it: https://gyazo.com/134fa2809520ef6a9753f5ab5c546dce

It’s a viewport frame with a clone of the player’s character, and every frame i set the clone’s body parts to have the same cframe as the original body parts and i set the viewport’s camera to have the same cframe as the workspace’s camera

how did u do that please help me