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NVIDIA On Turning Quake II into the First Fully Ray-Traced Game
Post by KostaAndreadis @ 02:24pm 15/04/19 | Comments
We chat with some of the engineers at NVIDIA and go behind the scenes of the impressive Quake II RTX mod

Powered by the company’s new line of Turing graphics cards, ray-tracing represents a major leap in the visual fidelity and realism found in real-time environments - with the flagship NVIDIA RTX 2080 Ti leading the charge. In March, NVIDIA took the stage at the Game Developers Conference (GDC) to showcase a new look at id Software’s seminal shooter Quake II. With the new part being that a team of engineers and artists at NVIDIA had gone and changed up all the lighting and other visual effects found in the 1997 classic and replaced them with cutting edge ray-tracing ones. In what’s being called Quake II RTX.

The Quake II RTX Demonstration from GDC

The demo was built off the impressive path-tracing mod created by Ph.D. student and former NVIDIA intern Christoph Schied from earlier in the year. In fact, like the rest of us, the engineering team at NVIDIA were impressed and fascinated by the results. Especially when you factor in the age of Quake II.

“We first heard of Christoph’s Q2VKPT [Quake II mod] sometime in late January shortly after it was released,” Principal DevTech Engineer Alexey Panteleev and lead programmer on Quake II RTX tells me. “We were not aware of the project before that. Originally, our intention was just to analyse and improve performance and fix some image quality issues. I started making some improvements, then everyone got excited, and then things really started cooking.”

A Technical Marvel - Looking Back at Quake II

“Quake II was already a pioneer in simulating many lighting effects,” NVIDIA’s Manuel Kraemer adds. “For instance, the first Quake is credited as the first game to store pre-computed diffuse lighting and occlusions into lightmaps. Because these ray-tracing calculations could not be performed in real time, much of the lighting in the game was static. Many shadows were also missing or incorrect. Although lightmaps have been greatly improved since, they remain a fundamental technique that is still used today in almost every game.”

“Quake II had no complex materials such as metal, water, or glass, because reflections and refractions would have had to be computed in real-time,” Manuel continues. “Many different techniques have been invented over the years to approximate these material properties. However, they all have limitations and often fall deep into the uncanny valley. Only ray tracing can produce physically correct reflections and refractions in every situation.”

The lack of reflections, simulated or not, is not exactly surprising for a game that came out at a time when films like Con Air, Titanic, and Face/Off were filling up movie theatres. As pointed out by NVIDIA, the fact that there weren’t any surfaces that reflected the player the avatar or player model in Quake II only consisted of a hand attached to a weapon. Which, on the receiving end, would no doubt be a lot scarier than coming across a Berserker.

"Many different techniques have been invented over the years to approximate these material properties. However, they all have limitations and often fall deep into the uncanny valley."

“id Software games have been a benchmark of innovation in interactive graphics for decades,” Manuel recalls pointing to Quake II not only as a memorable game but also a milestone in game visuals. “John Carmack is a legend among game developers, and he has been an inspiration for many of us. We can probably also credit him for motivating us to get through our advanced calculus and algebra classes. It was a lot of fun to try to figure the dark sorceries that were being used to render these amazing virtual worlds.”

The First Fully Ray-Traced Game

As it presented footage of Quake II RTX, NVIDIA demonstrated for the first time an interactive game where all lighting, reflections, shadows and VFX were ray-traced with no traditional effects or other techniques utilised. As one of the most complex and hardware intensive visual effects in the history of computing, this is in stark contrast to Battlefield V’s use of ray-tracing purely for reflections, Metro Exodus implementing the technology for global illumination, and Shadow of the Tomb Raider living up to its namesake with real-time ray-traced shadows.

“The main challenge with real-time ray tracing is keeping it real time while you increase the realism of rendered images and add various effects,” Alexey explains. “Typically, this is an iterative process where we find some optimisation that improves performance. Which then allows us to add more features, which in turn reveals other areas that we can improve upon.”

The original mod, as put together by Christoph Schied approached Quake II from the same direction as lighting found in modern computer-generated animation – referred to as path-tracing. “This project adds one more layer of complexity though: path-tracing typically requires tracing a lot of rays per pixel, think thousands,” Alexey continues. “However, in order to do path-tracing in real-time, we have to stay within a much smaller budget of around 5-10 rays per pixel. Which unfortunately results in very noisy images and removing this noise can be challenging.”

The Quake II RTX demo as presented on stage at GDC was created over a period of six weeks with the team size at NVIDIA growing to include 18 engineers and artists from across the company. “It was a science experiment,” Manuel adds. “We wanted to find the exact melting point of a Turing chip. We still don’t know, but the demo looks great!”

A Glimpse at The Future via The Past

Going back to Quake II to create and showcase the visual effects of the future isn’t as strange or crazy as it sounds. “At the pace of gaming technology, 20 years is the distant future,” Manuel explains noting that Quake II RTX is an exercise in figuring out or visualising the future. “Quake II RTX is more than just a ray tracing experiment, it is a real time, global illumination path tracer.” An more importantly, a game changer.

In describing the outcome, that’s exactly what it sounds like. “We use ray tracing technology to compute in real time a ‘global solution’ to the transport of light energies across the virtual world,” Manuel adds. “We account for direct light sources being reflected or refracted, but we also account for many indirect light paths that bounce between the objects, the floors, the walls, etc. This is still an approximation, and there is still a lot of room for improvements. However, high-fidelity dynamic global illumination, in real time, is a game changer.”

"It was a science experiment, we wanted to find the exact melting point of a Turing chip. We still don’t know, but the demo looks great!"

In speaking with the team, we were curious to find out if there was any collaboration between NVIDIA and id Software on the project. The graphics pioneer, after all, has a long-standing relationship with just about every major developer. “id Software is very busy working on Doom Eternal which we know everyone is looking forward to,” Alexey concludes. “We did not want to bother them, but we are pretty sure they will like what was done.” And with id Software continuing to focus on pushing game visuals and graphics forward, odds are they’re probably as delighted as fans are to see the work being done on this PC classic.

And with Quake II now in the hands of fans around the world with mods, tweaks, and the original version still being played – NVIDIA will follow suit. “Our goal is to publish an open source version of Quake II RTX.”

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