Saved GLTF is shifted relative to original model position

[goddard@…]

The following bug report has been submitted:
Platform:        macOS-14.6.1-arm64-arm-64bit
ChimeraX Version: 1.8 (2024-06-10 23:15:52 UTC)
Description
Saving GLTF for a model translated in the scene and using "center false" produces a file that does not align with the original when opened in ChimeraX.  It seems to apply the translation twice.

Log:
UCSF ChimeraX version: 1.8 (2024-06-10)  
© 2016-2024 Regents of the University of California. All rights reserved.  
How to cite UCSF ChimeraX  

> shape rectangle

> move x 2 models #1

> save test.glb center false

> open test.glb

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

> view




OpenGL version: 4.1 Metal - 88.1
OpenGL renderer: Apple M1 Max
OpenGL vendor: Apple

Python: 3.11.4
Locale: UTF-8
Qt version: PyQt6 6.6.1, Qt 6.6.1
Qt runtime version: 6.6.3
Qt platform: cocoa
Hardware:

    Hardware Overview:

      Model Name: MacBook Pro
      Model Identifier: MacBookPro18,2
      Model Number: MK1H3LL/A
      Chip: Apple M1 Max
      Total Number of Cores: 10 (8 performance and 2 efficiency)
      Memory: 32 GB
      System Firmware Version: 10151.140.19
      OS Loader Version: 10151.140.19

Software:

    System Software Overview:

      System Version: macOS 14.6.1 (23G93)
      Kernel Version: Darwin 23.6.0
      Time since boot: 8 days, 21 hours, 32 minutes

Graphics/Displays:

    Apple M1 Max:

      Chipset Model: Apple M1 Max
      Type: GPU
      Bus: Built-In
      Total Number of Cores: 32
      Vendor: Apple (0x106b)
      Metal Support: Metal 3
      Displays:
        Color LCD:
          Display Type: Built-in Liquid Retina XDR Display
          Resolution: 3456 x 2234 Retina
          Main Display: Yes
          Mirror: Off
          Online: Yes
          Automatically Adjust Brightness: No
          Connection Type: Internal


Installed Packages:
    alabaster: 0.7.16
    alphashape: 1.3.1
    appdirs: 1.4.4
    appnope: 0.1.4
    asttokens: 2.4.1
    Babel: 2.15.0
    beautifulsoup4: 4.12.3
    blockdiag: 3.0.0
    blosc2: 2.0.0
    build: 1.2.1
    certifi: 2023.11.17
    cftime: 1.6.4
    charset-normalizer: 3.3.2
    ChimeraX-AddCharge: 1.5.17
    ChimeraX-AddH: 2.2.6
    ChimeraX-AlignmentAlgorithms: 2.0.2
    ChimeraX-AlignmentHdrs: 3.5
    ChimeraX-AlignmentMatrices: 2.1
    ChimeraX-Alignments: 2.12.7
    ChimeraX-AlphaFold: 1.0
    ChimeraX-AltlocExplorer: 1.1.1
    ChimeraX-AmberInfo: 1.0
    ChimeraX-Arrays: 1.1
    ChimeraX-Atomic: 1.57.1
    ChimeraX-AtomicLibrary: 14.0.6
    ChimeraX-AtomSearch: 2.0.1
    ChimeraX-AxesPlanes: 2.4
    ChimeraX-BasicActions: 1.1.2
    ChimeraX-BILD: 1.0
    ChimeraX-BlastProtein: 2.4.6
    ChimeraX-BondRot: 2.0.4
    ChimeraX-BugReporter: 1.0.1
    ChimeraX-BuildStructure: 2.12.1
    ChimeraX-Bumps: 1.0
    ChimeraX-BundleBuilder: 1.2.7
    ChimeraX-ButtonPanel: 1.0.1
    ChimeraX-CageBuilder: 1.0.1
    ChimeraX-CellPack: 1.0
    ChimeraX-Centroids: 1.4
    ChimeraX-ChangeChains: 1.1
    ChimeraX-CheckWaters: 1.4
    ChimeraX-ChemGroup: 2.0.1
    ChimeraX-Clashes: 2.2.4
    ChimeraX-ColorActions: 1.0.5
    ChimeraX-ColorGlobe: 1.0
    ChimeraX-ColorKey: 1.5.6
    ChimeraX-CommandLine: 1.2.5
    ChimeraX-ConnectStructure: 2.0.1
    ChimeraX-Contacts: 1.0.1
    ChimeraX-Core: 1.8
    ChimeraX-CoreFormats: 1.2
    ChimeraX-coulombic: 1.4.3
    ChimeraX-Crosslinks: 1.0
    ChimeraX-Crystal: 1.0
    ChimeraX-CrystalContacts: 1.0.1
    ChimeraX-DataFormats: 1.2.3
    ChimeraX-Dicom: 1.2.4
    ChimeraX-DiffPlot: 1.0
    ChimeraX-DistMonitor: 1.4.2
    ChimeraX-DockPrep: 1.1.3
    ChimeraX-Dssp: 2.0
    ChimeraX-EMDB-SFF: 1.0
    ChimeraX-ESMFold: 1.0
    ChimeraX-FileHistory: 1.0.1
    ChimeraX-FunctionKey: 1.0.1
    ChimeraX-Geometry: 1.3
    ChimeraX-gltf: 1.0
    ChimeraX-Graphics: 1.1.1
    ChimeraX-Hbonds: 2.4
    ChimeraX-Help: 1.2.2
    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-IUPAC: 1.0
    ChimeraX-Label: 1.1.10
    ChimeraX-ListInfo: 1.2.2
    ChimeraX-Log: 1.1.6
    ChimeraX-LookingGlass: 1.1
    ChimeraX-Maestro: 1.9.1
    ChimeraX-Map: 1.2
    ChimeraX-MapData: 2.0
    ChimeraX-MapEraser: 1.0.1
    ChimeraX-MapFilter: 2.0.1
    ChimeraX-MapFit: 2.0
    ChimeraX-MapSeries: 2.1.1
    ChimeraX-Markers: 1.0.1
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    ChimeraX-MCopy: 1.0
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    ChimeraX-MLP: 1.1.1
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    ChimeraX-MMTF: 2.2
    ChimeraX-Modeller: 1.5.17
    ChimeraX-ModelPanel: 1.5
    ChimeraX-ModelSeries: 1.0.1
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    ChimeraX-Mole: 1.0
    ChimeraX-Morph: 1.0.2
    ChimeraX-MouseModes: 1.2
    ChimeraX-Movie: 1.0
    ChimeraX-Neuron: 1.0
    ChimeraX-Nifti: 1.2
    ChimeraX-NIHPresets: 1.1.18
    ChimeraX-NMRSTAR: 1.0.2
    ChimeraX-NRRD: 1.2
    ChimeraX-Nucleotides: 2.0.3
    ChimeraX-OpenCommand: 1.13.5
    ChimeraX-PDB: 2.7.5
    ChimeraX-PDBBio: 1.0.1
    ChimeraX-PDBLibrary: 1.0.4
    ChimeraX-PDBMatrices: 1.0
    ChimeraX-PickBlobs: 1.0.1
    ChimeraX-Positions: 1.0
    ChimeraX-PresetMgr: 1.1.1
    ChimeraX-PubChem: 2.2
    ChimeraX-ReadPbonds: 1.0.1
    ChimeraX-Registration: 1.1.2
    ChimeraX-RemoteControl: 1.0
    ChimeraX-RenderByAttr: 1.4.1
    ChimeraX-RenumberResidues: 1.1
    ChimeraX-ResidueFit: 1.0.1
    ChimeraX-RestServer: 1.2
    ChimeraX-RNALayout: 1.0
    ChimeraX-RotamerLibMgr: 4.0
    ChimeraX-RotamerLibsDunbrack: 2.0
    ChimeraX-RotamerLibsDynameomics: 2.0
    ChimeraX-RotamerLibsRichardson: 2.0
    ChimeraX-SaveCommand: 1.5.1
    ChimeraX-SchemeMgr: 1.0
    ChimeraX-SDF: 2.0.2
    ChimeraX-Segger: 1.0
    ChimeraX-Segment: 1.0.1
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    ChimeraX-SelInspector: 1.0
    ChimeraX-SeqView: 2.11.2
    ChimeraX-Shape: 1.0.1
    ChimeraX-Shell: 1.0.1
    ChimeraX-Shortcuts: 1.1.1
    ChimeraX-ShowSequences: 1.0.3
    ChimeraX-SideView: 1.0.1
    ChimeraX-Smiles: 2.1.2
    ChimeraX-SmoothLines: 1.0
    ChimeraX-SpaceNavigator: 1.0
    ChimeraX-StdCommands: 1.16.5
    ChimeraX-STL: 1.0.1
    ChimeraX-Storm: 1.0
    ChimeraX-StructMeasure: 1.2.1
    ChimeraX-Struts: 1.0.1
    ChimeraX-Surface: 1.0.1
    ChimeraX-SwapAA: 2.0.1
    ChimeraX-SwapRes: 2.5
    ChimeraX-TapeMeasure: 1.0
    ChimeraX-TaskManager: 1.0
    ChimeraX-Test: 1.0
    ChimeraX-TetraScapeCommand: 0.1
    ChimeraX-Toolbar: 1.1.2
    ChimeraX-ToolshedUtils: 1.2.4
    ChimeraX-Topography: 1.0
    ChimeraX-ToQuest: 1.0
    ChimeraX-Tug: 1.0.1
    ChimeraX-UI: 1.39.1
    ChimeraX-uniprot: 2.3
    ChimeraX-UnitCell: 1.0.1
    ChimeraX-ViewDockX: 1.4.3
    ChimeraX-VIPERdb: 1.0
    ChimeraX-Vive: 1.1
    ChimeraX-VolumeMenu: 1.0.1
    ChimeraX-vrml: 1.0
    ChimeraX-VTK: 1.0
    ChimeraX-WavefrontOBJ: 1.0
    ChimeraX-WebCam: 1.0.2
    ChimeraX-WebServices: 1.1.4
    ChimeraX-Zone: 1.0.1
    click: 8.1.7
    click-log: 0.4.0
    colorama: 0.4.6
    comm: 0.2.2
    contourpy: 1.2.1
    cxservices: 1.2.2
    cycler: 0.12.1
    Cython: 3.0.10
    debugpy: 1.8.1
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[Tom Goddard]

Fixed.

The ChimeraX position matrix was being applied both to the GLTF Mesh instance and the Node that contained the mesh due to the code that handle instancing forgetting to check if there was more than 1 instance (in which case the node gets the identity position).

Surprised no one noticed this. If a few models were shifted by different amounts they would not preserve the original alignment. I guess that case is rare.