id summary reporter owner description type status priority milestone component version resolution keywords cc blockedby blocking notify_on_close platform project 9001 Add a backface culling option when saving to GLTF format kristen.browne@… Tom Goddard "GLTF materials have a backface culling flag that tells the renderer whether to enable that option. The default is true, but an option to make it false would help for non-closed surfaces. From: ""Browne, Kristen (NIH/NIAID) [C]"" Subject: RE: [EXTERNAL] Re: gltf smoothing attribute: Date: May 11, 2023 at 5:04:39 PM PDT To: Tom Goddard I’m not too sure exactly how things are computed! I actually stumbled into this because when I was building the mesh repair workflow, I use the STL that is created from the GLB files. Those files were really faceted in the viewer because the “smoothing” information was stripped. Then it came up again when I needed to remove the default “smooth shading” preference in my renderings for devices etc. and saw that indeed this was being applied to the GLBs from ChimeraX . Troubleshooting errors in the mesh repair process I’ve been working on gave me the opportunity to really scrutinize the outputs in a way there just wasn’t time for before. One other thing that would be a totally optional feature request, would be to have a ChimeraX GUI option when outputting a glb to turn backface culling off. By default, most viewers optimize performance by not rendering the backfaces. When Phil was creating custom models that had a patch of surface in ChimeraX, they looked invisible when put in the viewer when viewed from the back. Same on Babylon and other GLTF viewers for web. I fixed them for him by extruding a second face. I could also manually update the gltf setting for backface culling. It is a gltf property of the material as they even have a toggle for it in the Babylon inspector: This is something that we can also do on our end, but it might be of wider use to your users that are also wanting to export models that have a surface like this and view it in a glb viewer like Babylon. I leave it up to you if it’s something you would like to incorporate! K " enhancement closed moderate Input/Output fixed Elaine Meng Eric Pettersen all ChimeraX