We describe a suite of open source virtual reality programs which can be used to visualize the results of chemical simulations of various types (including access to NOMAD, the largest database of materials science compounds). The programs target virtual reality environments at different price points (M(sic) CAVE-like(1) systems, commercial products such as the approximate to 500(sic) HTC Vive, approximate to 100(sic) Samsung GearVR, to approximate to 10(sic) Google Cardboards) in order to let final users select the device which best suits their needs. We provide a coherent interface, with graceful degradation of features for less capable devices. Tests with final users in the domains of materials science, theoretical chemistry, biochemistry and biological sciences show that the program can be used to solve certain problems much more easily and intuitively than with previous tools. Users in other fields (fluid dynamics, or climate research) were also interested in adopting the system. Applications to teaching, dissemination, outreach and marketing have also been successful. The system is currently implanted in several universities and enterprises. Additionally, outreach materials in the form of stereoscopic (panoramic) videos can be easily prepared from the viewer's output or the visualization pipeline. We describe the design and implementation of the system, and mention some caveats about using standard graphic optimization techniques in virtual reality environments. Program summary Program Title: NOMAD VR Program Files doi: http://dx.doi.org/10.17632/8n92hc8fbd.1 Licensing provisions: Apache-2.0 Programming language: Mainly C++; interface to Android and IOS in Java and Objective C, respectively Supplementary material: VR optimization caveats: example of graphic artifacts; NOMAD VR user study. Nature of problem: Understanding chemical materials and phenomena can be sometimes taxing. Visualization of simulations and exploration using mouse and keyboard interfaces, and the creation of illustrations and videos is helpful, but in some complex cases, it proves insufficient. The use of virtual reality tools allows users of NOMAD VR to enter the simulated world, providing easier interaction and understanding. Solution method: We have developed a virtual reality viewer for chemistry which has proven useful to help researchers understand their datasets better. Users may either upload their calculations to NOMAD in order to benefit from the centralized environment for data storage and analysis, or prepare their datasets for direct use in NOMAD VR using standard formats such as xyz or Gaussian cube. Workflows for different data types, using open source tools such as Paraview and Meshlab, are also provided. Tutorials for different usecases and a complete description of options can be seen at https://www.nomad-coe.eu/the-project/graphics/virtual-reality-configurator, which also includes a link to the User Manual. Additional comments including restrictions and unusual features: Download links to pre-compiled software and to the source code can be accessed from https://www.nomad-coe.eu/the-project/graphics/VR-prototype. As final users find additional use-cases and request additional functionality, more features are being implemented. We strive to maintain compatibility with previous builds by adding keywords to the configuration file to enable/disable new functionality. This article documents NOMAD VR as of 23/05/2018 (git commit 65a4204f7b0c6313d6ecd6586dc879ce281b857d). (C) 2018 Elsevier B.V. All rights reserved.
