Automakers are using virtual reality (VR) and augmented reality (AR) more and more in vehicle development. Both are incredibly useful tools that can help create digital versions of a car before physical parts are actually made. Those digital versions help improve everything from its design to quality control. However, despite the influx of so many new technologies, many car companies still use old-school full-size clay models of cars and BMW is one of them.

BMW is one of the most advanced automakers in the world, when it comes to manufacturing. The Bavarians dump tons of money into artificial intelligence (AI), automation, robotics, and VR for building its cars. However, it also spends quite a bit of money on clay models, with cars even as new as the BMW iX having been made in clay before production. But with all of BMW’s technological knowhow and capabilities, why does it still use clay?

This new video from Business Insider shows off how and why car companies still use clay, BMW included. It’s an interesting look at modern auto manufacturing and how it’s both evolved and stayed quite traditional.

Clay modeling is an art form in itself. Creating full-size, perfectly accurate clay models requires teams of incredibly talented experts, in totally top secret facilities, and tons of money. First, a based chassis is built from metal and wood. Then, on top of that, foam blocks are added to sort of give it the car’s basic shape. Finally, the clay is added and molded into the exact design that the car will become. To finalize its shape, expert craftspeople use fine hand tools to carve, cut, and chisel every last crease and body line. It’s genuinely astonishing to watch those talented people show off their expertise.

Why do car companies go through all of that time, effort, and money to make a car in clay, when both AR and VR already exist? Because there are things about a car’s design that can only be learned in person, such as the way its curves and lines react to natural sunlight. It’s also impossible to gauge a car’s size and scale without standing right next to it in person. VR simply can’t do that.

It’s also always fun to watch car companies test aerodynamics, as they take the finished clay model and put it in a wind tunnel. Then, someone with a smoke wand lets the smoke blow over the car, showing car companies exactly how air flows over the car’s body. It’s very satisfying to watch, for some reason.

Clay modeling is an art form that’s incredibly difficult and impressive but its also one that might never go away.