This Working Marauder's Map Built Using AR and GPS Brings Magic to Our World

Lucas Rizzotto’s AR Marauder’s Map infused with GPS.
Gif: Lucas Rizzotto

Many of the things we see on TV or movies can often only be explained with the word “magic” (or, your know, visual effects.) What would it be like if the magical inventions we see on our screens existed in real life? Now, at least one does, and you apparently don’t have to be a wizard in order to use it.

Virtual and augmented reality artist Lucas Rizzotto recently debuted a video made with his latest invention: a working Marauder’s map built using augmented reality, GPS technology, and image tracking. In case you need a refresher, the Marauder’s Map is a magical document that appears in the Harry Potter books and movies. It allows the owner to visualize all of Hogwarts, the wizarding school in the universe, and locate every person in its corridors and grounds.

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The creation is part of Rizzotto’s YouTube series called Lucas Builds the Future, which features him building “something crazy,” from a virtual reality time machine to an augmented reality portal to see his best friend, every episode. Rizzotto’s videos and inventions are community-funded through fan donations on Patreon.

Through his videos, we’ve learned that when Rizzotto takes on a new project, he likes to go all out. (The man once decided to film his life for a year wearing Snapchat Spectacles 3 in order to build a VR time machine). With this in mind, it was no surprise when Rizzotto said that he had rented out a castle on Airbnb to build his Marauder’s Map and film his new video. He called the castle, “Tiny Hogwarts.”

To build the map, Rizzotto had to do three things: figure out how to track and feature the people at the castle on the map, draw a visually appealing and accurate map of said castle, and figure out how to make the map “magically” appear.

For the first part, he decided to create an app that sends a person’s GPS coordinates to a server every second. This generated a series of pink dots representing the peoples’ locations, which he replaced with name ribbons similar to the ones that appear in the original Marauder’s Map. Since the movie map was also famous for showing the small disappearing footsteps of the people walking around in the castle, Rizzotto wrote a script that tracks the direction that someone is moving in and creates footprints behind them.

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Of course, footsteps don’t tell you much without an accurate blueprint of the lay of the land. Rizzotto proceeded to fly a drone over the castle to help him draw his Marauder’s Map, but upon realizing that he “can’t draw for shit,” he decided to design it in Photoshop. Step two, check.

The final task needed to make his Marauder’s Map consisted of combining two technologies: augmented reality and image tracking. AR allows creators to add digital objects that appear to exist in the real world. For Rizzotto’s map, he would essentially overlay the image on his map, made of a real piece of parchment.

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Rizzotto says he ran into challenges with the AR because he wanted to use black lines on his map to ensure it looked as realistic as possible. But using blank ink meant that he wouldn’t be able to use an AR headset. These devices have transparent displays and are therefore incapable of creating the color black using light. This meant that he would have to use his phone, which has a black screen and is another way to view AR, for the map. (Check out Google search’s AR animals for an example of what AR with your phone looks like.)

Image tracking was also an important final piece of the puzzle. This would allow him to build his AR experience on top of printed images. Per Rizzotto, image tracking works best when there are images with a lot of visual contrasts and details, which is easier for the computer to detect. So, a blank piece of parchment wouldn’t do, which meant it was time to take out Photoshop again and add some design flourishes.

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For the finishing touch, Rizzotto created an ink dissolve shader to make the map appear and disappear and added voice commands so that the map would only appear if he said the words, “I solemnly swear I’m up to no good.” When he tested out the map in the video, the experience was truly almost like watching a movie. There’s Rizzotto inside the castle, and two little ribbons moving around on the map. These are Rizzotto’s friends, whom he invited over to the castle to test out his new creation.

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Asked why he decided to create a Marauder’s Map, Rizzotto cited science fiction writer and futurist Arthur C. Clarke, one of the co-writers of 2001: A Space Odyssey, who once said: “Any sufficiently advanced technology is indistinguishable from magic.” Rizzotto explained that he wanted to create a living example of this by bringing something to life that we understood as “magical and impossible to create.”

“If you took the technology we have today back to the 1700s, people would simply have no idea how any of it works—much less how any of it is even possible,” he said. “They’d look at it as magic, even though to us it’s just a normal part of day to day life. The same reasoning can be applied to us today. Bring back technology from 100 years into the future and we would [also] perceive it in the same way.”

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(Editor’s note: Gizmodo does not support J.K. Rowling, creator of the Harry Potter franchise in which the Marauder’s Map appears, or her transphobic views. This blog aims to showcase unaffiliated fan work.)

Rizzotto said via Twitter direct messages that his Marauder’s Map was totally independent of J.K. Rowling and Warner Bros., adding that he believed neither party knew about it. When asked whether he was concerned about the controversy surrounding Rowling when creating an invention from the Harry Potter universe, Rizzotto said he wasn’t too worried.

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“I have been planning on doing this for almost a year,” he told Gizmodo. “Her work is a relevant piece of pop culture that we can still use ... as a platform to explore ideas and educate people.”

In the end, it’s clear that even if magic doesn’t exist in our world, it can still inspire us to dream up inventions beyond our reach today and use science and technology to make them a reality. Who knows, maybe the next great invention will allow us to instantly travel from one place to another—another thing that’s possible in the Harry Potter universe —once we can travel normally, that is.

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