-Croteam CTO Davor Hunski explores Serious Sam’s need for large environmental scope.

In an interview for Ars Technica’s War Stories series, Croteam’s chief creative officer Davor Hunski tells the story of how Serious Sam’s hand-made engine came to be and how a vertical slice demo ultimately saved the game.

Hunski explains how the early Serious Sam development team set their sights on a first-person shooter game and, lacking the funds to use a big-name engine, set out to create their own 2D Wolfenstein-like engine.

However, as technology continued to evolve throughout the project’s development, games like Duke Nukem and Quake came out and offered features that made the team’s 2D engine something that was no longer viable.

Instead, Hunski explains that they aimed to stand out from the crowd by creating an engine that could handle 10 times the on-screen enemies and projectiles that other games of the time featured. 

“So, we invented this caching ahead system, where one projectile or moving object would actually cache [maybe] three or four seconds ahead, everything that it could collide and until nothing changed during those three, four seconds, it wouldn't have to test again against an environment for collision,” says Hunski.

“To speed up the collision, we were not able to use real geometry of cubes for collision. But we approximated them with several spheres," he explains. "On the one side, it sped up immensely our collision tests, because actually a test with a cube is a really, really easy one. And the second gain that we got is that we could have multidirectional gravities so characters would be able to walk on ceilings, inside the spheres, so we had several types of gravity and we actually put that into the game as secret places locations, and that was really, really awesome.”

Hunksi’s full explanation of that early engine tech and how a lone positive review of a vertical slice demo can be found in the full video just above.