Humanity first set foot on the moon on July 20th, 1969. There is mission data, video, and photos of the event, but a startling number of people still subscribe to the conspiracy theory that we never went to the moon at all. They insist it was all done on a soundstage, and the proof is right there in the video. This claim has been debunked many times over the years, but now Nvidia is thumping the conspiracy theorists one more time in order to show off the power of its new Maxwell GPU.
Maxwell is Nvidia’s latest and greatest graphics architecture powering the blisteringly fast GTX 980 and GTX 970. One of the technologies Nvidia is particularly proud of is called Voxel Global Illumination (VXGI). It’s an advanced computation algorithm that allows the Maxwell GPU core to accurately render global illumination with indirect lighting. It is this technology that Nvidia used to build a complete mockup of the Apollo 11 landing site in the Unreal 4 game engine.
One of the photos conspiracy theorists point to as proof that man did not go to the moon is a rather famous image of Buzz Aldrin coming down the lunar lander ladder, which was taken by Neil Armstrong. Because Aldrin is on the shadowy side of the lander, the moon landing deniers claim he should not be illuminated as he appears to be. That means more than one light source (the sun), and thus it could not have been taken on the moon. Nvidia’s simulation is yet more evidence of just how wrong that claim is.
Most people have a general conception of light as a beam that hits an object and then bounces off at a certain angle, but that’s not how it works. Light is scattered in all directions, and can bounce off a few objects with high enough reflectivity. Nvidia had to generate realistic values for the reflectivity (or albedo) of all the element in its simulated moon landing site. The lunar soil, the rover, the space suits–everything. When all this was input and VXGI was set loose, the scene looked pretty good, but it wasn’t perfect. There wasn’t enough light on Aldrin.
Nvidia scoured the footage of that moment looking for another reflective object, and then they realized–it was Armstrong. Space suits have very high albedo, so Armstrong himself was acting like a mirror bouncing more light at Aldrin when he took the picture. The addition of this made the scene perfect. It’s a startlingly good match for the original and a testament to how well Maxwell can simulate light. Nvidia also showed how the starscape was blotted out in photos by the bright foreground light (another conspiracy theorist favorite).
Global illumination has been used in CGI for movies over the years, which is why a high-end film always looks more real than even the best video games. The difference being the movie is pre-rendered and a game is rendered as you play it. Maxwell makes it possible to generate indirect lighting in real time using a voxel map, or approximation of the scene. Even with the simplified voxel surfaces, the footage Nvidia is showing off looks amazing.
