Math is hard, but Space Math is even harder. If you can imagine all the complex physics calculations that go into moving a videogame character around a 3D space, think about how much harder it would be if that level was also moving around a 3D space. That's the conundrum Digital Extremes was facing when it first conceived of ship-to-ship space combat almost ten years ago—a problem it finally managed to solve in Warframe's upcoming Empyrean update.

If you missed out on all the big Warframe news from its annual Tennocon convention last weekend, the gist is that Warframe is getting an expansion where you can build spaceships and fly them with three of your friends. At any time, you can leave your ship to board enemy ships or explore ruins floating in space. It all looks really ambitious and exciting.

But the physics calculations necessary to have ships that players can walk around in that are also pitching and yawing through 3D space are extremely complex and demanding. That's why, as detailed in our extensive interview with game director Steve Sinclair, Digital Extremes originally abandoned the idea when it was first prototyping Warframe over a decade ago. But as Sinclair explains, that fantasy of space ninjas piloting spaceships stuck with him and he was eventually able to solve the problem using some clever tricks.

You should watch the Empyrean demo above so you have a reference for what I'm about to explain. As you can see in the demo, the player takes control of the ship and flies around space and it all looks just like it does in any other space game like Star Citizen or No Man's Sky. But here's the trick: The ship isn't actually moving.

Instead, Digital Extremes is using an ancient rendering technique called 'portal rendering' which works almost exactly like it does in the puzzle game Portal. Essentially, you create a portal or a window that is attached to somewhere else in 3D space, and when you look through it you see from a different perspective. The cockpit of Warframe's spaceship is actually one big portal into an entirely separate map.

'Trick' of our space battles is an ancient rendering technique twisted. You see your ship interior but windows are a portal attached to the RailJack entity itself in the combat zone which itself looks into the art space 'skybox'. Board the Obelisk, you see space from its entity. pic.twitter.com/4LRkdJBdYjJuly 8, 2018

"You just connect the player controls to where that portal is," Sinclair said in our interview. "For Empyrean, there's a big 32 kilometer-squared space where all the space combat is happening and you're pitching around and it feels like you might vomit, but [off to the side] there's a little level and that's your actual spaceship. You have a solid, reliable physics system driving what appears to be this six degrees of freedom experience over here [in an entirely separate area]."

The trick is apparently so clever, even some of Digital Extremes' own programmers were confused by it. "The idea was so sound that last week—last friggin' week—one of the graphics engineers, who is a way better programmer than me, said 'I think this is a problem because the level is rotating too fast.'" Sinclair told me. "And I'm like, whoa, pump the brakes. The level doesn't move. It's fixed in space and we're just moving the backdrop perspective."

If players leave the ship, they're then teleported into that real section of virtual space where they see a model of the spaceship their friends are piloting—but it's not the actual spaceship with full rendered interiors.

Whereas games like Star Citizen strive to simulate spaceflight more directly, that comes at an enormous burden to both the game engine, the computer playing the game, and the developers who have to stitch it altogether. "I'm going to fake it because I can make it faster," Sinclair laughed.

Thanks to lots of nuanced lighting and spatial effects, the trick works. From the demo, it's impossible to tell that you're not actually flying in 3D space.

That's just one of the cool tidbits that came from my time at Digital Extremes offices last weekend. Read the full interview to get a more in-depth look at the challenges Digital Extremes faced when making Empyrean, and check out my overview of all its cool features for more on why it's so exciting.