Issue link: https://digital.copcomm.com/i/863766
j u ly . a u g u s t 2 0 1 7 c g w 2 3 lot of the unnecessary detail removed. A high-res image of the Earth can be seen outside the ISS; that model is courtesy of game developer Opaque, with whom NASA has a collaborative relationship. In fact, other CG models used in the application are supplied by another col- laborator, Fusion VR, makers of the "Mars 2030" VR application (see "Gravitational Pull," July.August 2016). "This hearkens back to our idea of leveraging the games industry. These developers are interested in creating an authentic gaming expe- rience for their audience, to show what it is really like to be a NASA astronaut," says Noyes. "That is valuable to us from a PR standpoint. We want the public to be engaged in what NASA does, and we think games are an excellent medium to make that experience more authentic. On the flip side, we can also take some of their as- sets and make high-performance, visually appealing models and incorporate them into a practical NASA application." Some of the lab's CG models were im- ported from additional NASA applications, while others were hand modeled within open-source Blender or were digitally scanned. Texturing was accomplished with Allegorithmic's Substance. The system also uses Nvidia's VRWorks, as well as the company's PhysX, which supports con- servation of momentum and basic friction calculations. While PhysX is not as accurate as a high-fidelity simulation, the real-time physics engine can make astronauts feel like they are in space," says Noyes. The crew also uses Flex, an Nvidia GPU-accelerated, particle-based simula- tion library that supports so-body fluid mechanics. "We have a lot of applications for so-body physics in VR in real time, showing how astronauts drink water in space, for example, which is very non- intuitive as to how they would do it on Earth," explain Noyes. Flex is also great for implementing tether simulations, which are critical for a space walk. As for the physical elements used within the HRL applications, the lab reproduces inexpensive 3D-printed replicas of objects they scan. "There are small artifacts, but the visual fidelity is far more accurate than if it is hand modeled," says Noyes. "And we can 3D-print it almost immediately." An HTC Vive is used to navigate within the virtual space. A pair of Vive stations en- ables two people to occupy the same phys- ical space and conduct tasks in tandem. According to Noyes, NASA was attracted to the Vive's Lighthouse tracking system. "It has good performance versus price, and it is a decentralized system," he adds. We may switch to a different solution in the future if our requirements change, but for now, the Vive meets our requirements." Currently, the room-scale tracking has proven sufficient, to a point. NASA is using the hybrid-reality system with ARGOS, which has a much larger tracking area than what is supported by the Vive. "We are counting on the Lighthouse protocol, not the current implementation, which is designed to allow for essentially unlimited tracking volume using more base stations," says Noyes. "We think that will probably be solved in the near future, so we continu- ing to use Lighthouse as our solution. We are also exploring other solutions that are based on inside-out tracking that would remove the need for bases stations." Furthermore, the group is using the HTC puck instead of the main controllers for tracking the physical objects used in the hybrid-reality applications, since they are more compact. In early versions, lab person- nel attached the Vive tracker puck directly onto 3D-printed tools for tracking purposes. "We duct-taped it on, and it just worked," says Noyes. "In VR, you would see this physically-based rendered tool that looked like metal because we added a metal shader to it. We don't have to make it look accurate in the real world, it just has to feel accurate both geometrically and tactilely." A process that adds a thin layer of metal to the plastic object can achieve that latter objective. In the future, the team plans to integrate the electronics of the Vive tracking system TOP: DEMONSTRATING THE USE OF 3D-PRINTED TOOLS IN MIXED REALITY. BOTTOM: AN HRL VIRTUAL ENVIRONMENT.