Saving a GLTF file of a transparent surface shows as opaque in BabylonJS

[goddard@…]

The following bug report has been submitted:
Platform:        Windows-10-10.0.19044
ChimeraX Version: 1.5 (2022-11-24 00:03:27 UTC)
Description
Saving a GLTF file of a transparent and opening it in BabylonJS web viewer shows an opaque surface.  It can be made transparent in BabylonJS by changing the material alpha mode to blend.  There is a GLTF Material attribute called alphaMode that defaults to opaque even when transparent alpha values are given.  The GLTF file needs to set the material alphaMode attribute to blend to get this to work properly.  ChimeraX reads the GLTF file and shows the transparency correctly because it ignores the alphaMode attribute and always uses the alpha values for transparency.

Log:
Could not find tool "Tabbed Toolbar"  
UCSF ChimeraX version: 1.5 (2022-11-24)  
© 2016-2022 Regents of the University of California. All rights reserved.  
How to cite UCSF ChimeraX  

> open 1080 format ccp4 fromDatabase emdb

Opened emdb 1080 as #1, grid size 100,100,100, pixel 2.7, shown at level 1.68,
step 1, values float32  

> volume #1 color #b2b2b232

> save test.glb

> open test.glb

Opened glTF file containing 1 scenes, 3 nodes, 1 meshes  

> hide #!2 models

> show #!2 models

> hide #!1 models




OpenGL version: 3.3.0 NVIDIA 528.24
OpenGL renderer: Quadro P6000/PCIe/SSE2
OpenGL vendor: NVIDIA Corporation

Python: 3.9.11
Locale: en_US.cp1252
Qt version: PyQt6 6.3.1, Qt 6.3.1
Qt runtime version: 6.3.2
Qt platform: windows

Manufacturer: Gigabyte Technology Co., Ltd.
Model: To be filled by O.E.M.
OS: Microsoft Windows 10 Home (Build 19044)
Memory: 66,135,482,368
MaxProcessMemory: 137,438,953,344
CPU: 8 Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
OSLanguage: en-US

Installed Packages:
    alabaster: 0.7.12
    appdirs: 1.4.4
    asttokens: 2.1.0
    Babel: 2.11.0
    backcall: 0.2.0
    blockdiag: 3.0.0
    build: 0.8.0
    certifi: 2022.9.24
    cftime: 1.6.2
    charset-normalizer: 2.1.1
    ChimeraX-AddCharge: 1.4
    ChimeraX-AddH: 2.2.1
    ChimeraX-AlignmentAlgorithms: 2.0
    ChimeraX-AlignmentHdrs: 3.2.1
    ChimeraX-AlignmentMatrices: 2.0
    ChimeraX-Alignments: 2.6
    ChimeraX-AlphaFold: 1.0
    ChimeraX-AltlocExplorer: 1.0.3
    ChimeraX-AmberInfo: 1.0
    ChimeraX-Arrays: 1.0
    ChimeraX-Atomic: 1.41.5
    ChimeraX-AtomicLibrary: 8.0.3
    ChimeraX-AtomSearch: 2.0.1
    ChimeraX-AxesPlanes: 2.3
    ChimeraX-BasicActions: 1.1.2
    ChimeraX-BILD: 1.0
    ChimeraX-BlastProtein: 2.1.2
    ChimeraX-BondRot: 2.0.1
    ChimeraX-BugReporter: 1.0.1
    ChimeraX-BuildStructure: 2.7.1
    ChimeraX-Bumps: 1.0
    ChimeraX-BundleBuilder: 1.2
    ChimeraX-ButtonPanel: 1.0.1
    ChimeraX-CageBuilder: 1.0.1
    ChimeraX-CellPack: 1.0
    ChimeraX-Centroids: 1.3.1
    ChimeraX-ChangeChains: 1.0.2
    ChimeraX-CheckWaters: 1.3
    ChimeraX-ChemGroup: 2.0
    ChimeraX-Clashes: 2.2.4
    ChimeraX-ColorActions: 1.0.3
    ChimeraX-ColorGlobe: 1.0
    ChimeraX-ColorKey: 1.5.2
    ChimeraX-CommandLine: 1.2.4
    ChimeraX-ConnectStructure: 2.0.1
    ChimeraX-Contacts: 1.0.1
    ChimeraX-Core: 1.5
    ChimeraX-CoreFormats: 1.1
    ChimeraX-coulombic: 1.3.2
    ChimeraX-Crosslinks: 1.0
    ChimeraX-Crystal: 1.0
    ChimeraX-CrystalContacts: 1.0.1
    ChimeraX-DataFormats: 1.2.2
    ChimeraX-Dicom: 1.1
    ChimeraX-DistMonitor: 1.3
    ChimeraX-DockPrep: 1.0
    ChimeraX-Dssp: 2.0
    ChimeraX-EMDB-SFF: 1.0
    ChimeraX-ExperimentalCommands: 1.0
    ChimeraX-FileHistory: 1.0.1
    ChimeraX-FunctionKey: 1.0.1
    ChimeraX-Geometry: 1.2
    ChimeraX-gltf: 1.0
    ChimeraX-Graphics: 1.1
    ChimeraX-Hbonds: 2.4
    ChimeraX-Help: 1.2.1
    ChimeraX-HKCage: 1.3
    ChimeraX-IHM: 1.1
    ChimeraX-ImageFormats: 1.2
    ChimeraX-IMOD: 1.0
    ChimeraX-IO: 1.0.1
    ChimeraX-ItemsInspection: 1.0.1
    ChimeraX-Label: 1.1.7
    ChimeraX-ListInfo: 1.1.1
    ChimeraX-Log: 1.1.5
    ChimeraX-LookingGlass: 1.1
    ChimeraX-Maestro: 1.8.2
    ChimeraX-Map: 1.1.2
    ChimeraX-MapData: 2.0
    ChimeraX-MapEraser: 1.0.1
    ChimeraX-MapFilter: 2.0
    ChimeraX-MapFit: 2.0
    ChimeraX-MapSeries: 2.1.1
    ChimeraX-Markers: 1.0.1
    ChimeraX-Mask: 1.0.1
    ChimeraX-MatchMaker: 2.0.9
    ChimeraX-MDcrds: 2.6
    ChimeraX-MedicalToolbar: 1.0.2
    ChimeraX-Meeting: 1.0.1
    ChimeraX-MLP: 1.1
    ChimeraX-mmCIF: 2.8
    ChimeraX-MMTF: 2.2
    ChimeraX-Modeller: 1.5.6
    ChimeraX-ModelPanel: 1.3.6
    ChimeraX-ModelSeries: 1.0.1
    ChimeraX-Mol2: 2.0
    ChimeraX-Mole: 1.0
    ChimeraX-Morph: 1.0.1
    ChimeraX-MouseModes: 1.1.1
    ChimeraX-Movie: 1.0
    ChimeraX-Neuron: 1.0
    ChimeraX-Nucleotides: 2.0.3
    ChimeraX-OpenCommand: 1.9.1
    ChimeraX-PDB: 2.6.8
    ChimeraX-PDBBio: 1.0
    ChimeraX-PDBLibrary: 1.0.2
    ChimeraX-PDBMatrices: 1.0
    ChimeraX-PickBlobs: 1.0.1
    ChimeraX-Positions: 1.0
    ChimeraX-PresetMgr: 1.1
    ChimeraX-PubChem: 2.1
    ChimeraX-ReadPbonds: 1.0.1
    ChimeraX-Registration: 1.1.1
    ChimeraX-RemoteControl: 1.0
    ChimeraX-RenumberResidues: 1.1
    ChimeraX-ResidueFit: 1.0.1
    ChimeraX-RestServer: 1.1
    ChimeraX-RNALayout: 1.0
    ChimeraX-RotamerLibMgr: 2.0.1
    ChimeraX-RotamerLibsDunbrack: 2.0
    ChimeraX-RotamerLibsDynameomics: 2.0
    ChimeraX-RotamerLibsRichardson: 2.0
    ChimeraX-SaveCommand: 1.5.1
    ChimeraX-SchemeMgr: 1.0
    ChimeraX-SDF: 2.0
    ChimeraX-Segger: 1.0
    ChimeraX-Segment: 1.0
    ChimeraX-SelInspector: 1.0
    ChimeraX-SeqView: 2.7.2
    ChimeraX-Shape: 1.0.1
    ChimeraX-Shell: 1.0.1
    ChimeraX-Shortcuts: 1.1.1
    ChimeraX-ShowSequences: 1.0.1
    ChimeraX-SideView: 1.0.1
    ChimeraX-Smiles: 2.1
    ChimeraX-SmoothLines: 1.0
    ChimeraX-SpaceNavigator: 1.0
    ChimeraX-StdCommands: 1.10
    ChimeraX-STL: 1.0
    ChimeraX-Storm: 1.0
    ChimeraX-StructMeasure: 1.1
    ChimeraX-Struts: 1.0.1
    ChimeraX-Surface: 1.0
    ChimeraX-SwapAA: 2.0.1
    ChimeraX-SwapRes: 2.1.3
    ChimeraX-TapeMeasure: 1.0
    ChimeraX-Test: 1.0
    ChimeraX-Toolbar: 1.1.2
    ChimeraX-ToolshedUtils: 1.2.1
    ChimeraX-Tug: 1.0.1
    ChimeraX-UI: 1.24.3
    ChimeraX-uniprot: 2.2.1
    ChimeraX-UnitCell: 1.0.1
    ChimeraX-ViewDockX: 1.1.4
    ChimeraX-VIPERdb: 1.0
    ChimeraX-Vive: 1.1
    ChimeraX-VolumeMenu: 1.0.1
    ChimeraX-VTK: 1.0
    ChimeraX-WavefrontOBJ: 1.0
    ChimeraX-WebCam: 1.0.1
    ChimeraX-WebServices: 1.1.0
    ChimeraX-Zone: 1.0.1
    colorama: 0.4.5
    comtypes: 1.1.10
    cxservices: 1.2
    cycler: 0.11.0
    Cython: 0.29.32
    debugpy: 1.6.4
    decorator: 5.1.1
    docutils: 0.19
    entrypoints: 0.4
    executing: 1.2.0
    filelock: 3.7.1
    fonttools: 4.38.0
    funcparserlib: 1.0.1
    grako: 3.16.5
    h5py: 3.7.0
    html2text: 2020.1.16
    idna: 3.4
    ihm: 0.33
    imagecodecs: 2022.7.31
    imagesize: 1.4.1
    importlib-metadata: 5.1.0
    ipykernel: 6.15.3
    ipython: 8.4.0
    ipython-genutils: 0.2.0
    jedi: 0.18.1
    Jinja2: 3.1.2
    jupyter-client: 7.3.4
    jupyter-core: 5.1.0
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    lz4: 4.0.2
    MarkupSafe: 2.1.1
    matplotlib: 3.5.2
    matplotlib-inline: 0.1.6
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    nest-asyncio: 1.5.6
    netCDF4: 1.6.0
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    openvr: 1.23.701
    packaging: 21.3
    ParmEd: 3.4.3
    parso: 0.8.3
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    pip: 22.2.2
    pkginfo: 1.8.3
    platformdirs: 2.5.4
    prompt-toolkit: 3.0.33
    psutil: 5.9.1
    pure-eval: 0.2.2
    pycollada: 0.7.2
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    Pygments: 2.12.0
    PyOpenGL: 3.1.5
    PyOpenGL-accelerate: 3.1.5
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    tinyarray: 1.2.4
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    wcwidth: 0.2.5
    webcolors: 1.12
    wheel: 0.37.1
    wheel-filename: 1.4.1
    WMI: 1.5.1
    zipp: 3.11.0

[Tom Goddard]

Fixed.

Made gltf writer set material alphaMode to blend if drawing is transparent.