GOAL: In runtime (in a build, not in the editor), export a Static Mesh to GLTF. Subsequently (after re-launch) load the exported GLTF as a static mesh.
What works for me so far:
What does not work for me yet:
- Exporting using the ‘Export to GLTF’ blueprint node. This consistently results in a segfault dereferencing some nearly-null address. I have not yet tried to rebuild for debugging.
- According to the documentation, all of the pins except ‘File Path’ can be left unconnected and will have sensible default behavior. This also results in a segfault.
- I can’t set breakpoints in the plugin code (probably because I’m working with downloaded builds instead of built from source for debug) so I don’t know what invocation works in the editor, or where the blueprint version fails.
- The documentation
If someone has a blueprint that works for them that they could share, that would be wonderful!
Another option would be guidance on using the C++ API to work with a static mesh, since I can’t find a clear example in the code.
(Otherwise, advice on how to get a debugger attached to a plugin would also be welcome.)
Thanks for reading / helping
@UE_FlavienP - it seems like you are the expert? 
I’ve found where & why the crash occurs
In GLTFJsonBuilder.cpp
FGLTFJsonBuilder::FGLTFJsonBuilder(const FString& FileName, const UGLTFExportOptions* ExportOptions)
: FGLTFFileBuilder(FileName, ExportOptions)
, DefaultScene(JsonRoot.DefaultScene)
{
JsonRoot.Asset.Generator = GetGeneratorString();
if (ExportOptions->bIncludeCopyrightNotice)
{
JsonRoot.Asset.Copyright = GetCopyrightString();
}
}
The crash occurs because ExportOptions == nullptr.
However, according to the blueprint node documentation a null argument should be fine.
From GLTFExporter.h
/**
* Export the specified object to a glTF file (.gltf or .glb)
*
* @param Object The object to export (supported types are UMaterialInterface, UStaticMesh, USkeletalMesh, UWorld, UAnimSequence, ULevelSequence, ULevelVariantSets). Will default to the currently active world if null.
* @param FilePath The filename on disk to save as. Associated textures and binary files will be saved in the same folder, unless file extension is .glb - which results in a self-contained binary file.
* @param Options The various options to use during export. Will default to the project's user-specific editor settings if null.
* @param SelectedActors The set of actors to export, only applicable if the object to export is a UWorld. An empty set results in the export of all actors.
* @param OutMessages The resulting log messages from the export.
*
* @return true if the object was successfully exported
*/
UFUNCTION(BlueprintCallable, Category = "Miscellaneous", meta=(AutoCreateRefTerm="SelectedActors"))
static bool ExportToGLTF(UObject* Object, const FString& FilePath, const UGLTFExportOptions* Options, const TSet<AActor*>& SelectedActors, FGLTFExportMessages& OutMessages);
Reviewing the call stack there does not appear to be a point where default options are retrieved, so this looks like a bug to me.
I had previously also failed to export when options were not null, so I will try that and post again soon…
Minimal working blueprint:
Something observations:
- Selected Actors still can be null
- Options cannot be null, but does not need to be a persistent variable (unless you want to configure it)
NOTE: I have not been able to figure out how to make a GLTFExportOptions asset in the project, and the property-by-property configuration in a blueprint is… verbose. It would be very nice to have either:
- A split, even if it’s huge, since defaulted values can be hidden
- A configuration of a variable in the Editor Details view
- Guidance on how to create and configure an asset
