# VRChem: A Virtual Reality Molecular Builder
### Existing Molecular Modeling VR Applications  
Various VR applications for molecular modeling, visualization and other tasks have been developed previously [18; 26; 27; 28]. We examined some of these applications for inspiration and assessed their functionality and usability before beginning our own development. We have likewise inspected most new software released after the start of VRChem development in late 2016. Here we focus mainly on software geared towards molecular systems, but the VR learning environments focusing on crystallography and solid-state materials have been reviewed recently [29].  
The two most notable pieces of software we examined before our own development were Molecular Rift [30] and Caffeine [31] molecular viewer. Both were among the first pieces of chemical visualization and modeling software to target modern consumer-grade VR devices. Molecular Rift is an open-source application and features a novel user interface based on hand gestures that lets the user load a molecule from a file or an Internet repository and examine it in VR. The Caffeine molecular viewer is intended for similar use and features an impressive array of visualization modes and rendering performances. However, despite being seemingly well developed applications, both were built for visualization only and do not feature any molecule editing capabilities. Given that we believe molecular interactivity to be important in educational use, this shortcoming drove us to develop our own software instead.  
Since the inception of VRChem, several new applications have been released. ChemPreview [32] is a prototype piece of visualization software for unreleased Meta Augmented Reality glasses that has some basic editing capabilities. NomadVR [33] is another piece of visualization software designed to work natively on all VR platforms, but it does not allow editing the structure being seen. The very capable and interesting Narupa [34] software is capable of some structural editing, but was not originally designed for building molecules from scratch. However, the separate Narupa builder [35] software is much better suited for molecular modeling in VR, and is one of two application alongside VRChem we have found which features robust structure editing. Similarly to VRChem, Narupa builder enables energy minimization of the molecular structures with OpenBabel library [36]. The workflow of Narupa builder differs from what is commonly used in other modeling software, but it makes it quick to learn and is not a detriment to its usage. The builder includes a built-in library of common molecular fragments (rings, amino acids, etc.) for composing large structures. Additionally, Narupa builder was released under an open-source license, like VRChem. Nanome [37] is another piece of software with full structure editing capabilities, and it has been used in a relatively large-scale undergraduate biochemistry class with tetherless VR technology (Oculus Quest) [38]. Though the molecule building UI is unnecessarily menu-dependent and in our view could be streamlined, the software has superior visualization, protein editing and multi-user support. The software, however, is not free nor open-source, and it is thus not fully available for free educational or general use.