To use, make a new class extending GLTFDocumentExtension, override any methods you need, make an instance of your class, and register it using [method GLTFDocument.register_gltf_document_extension].
[b]Note:[/b] Like GLTFDocument itself, all GLTFDocumentExtension classes must be stateless in order to function properly. If you need to store data, use the [code]set_additional_data[/code] and [code]get_additional_data[/code] methods in [GLTFState] or [GLTFNode].
Runs when converting the data from a Godot scene node. This method can be used to process the Godot scene node data into a format that can be used by [method _export_node].
Part of the export process. This method is run after [method _get_saveable_image_formats] and before [method _export_post]. If this [GLTFDocumentExtension] is used for exporting images, this runs after [method _serialize_texture_json].
This method can be used to modify the final JSON of each node. Data should be primarily stored in [param gltf_node] prior to serializing the JSON, but the original Godot [param node] is also provided if available. The node may be null if not available, such as when exporting glTF data not generated from a Godot scene.
The return value is used to determine if this [GLTFDocumentExtension] instance should be used for exporting a given glTF file. If [constant OK], the export will use this [GLTFDocumentExtension] instance. If not overridden, [constant OK] is returned.
This method can be used to alter the state before performing serialization. It runs every time when generating a buffer with [method GLTFDocument.generate_buffer] or writing to the file system with [method GLTFDocument.write_to_filesystem].
Runs when generating a Godot scene node from a GLTFNode. The returned node will be added to the scene tree. Multiple nodes can be generated in this step if they are added as a child of the returned node.
Returns the file extension to use for saving image data into, for example, [code]".png"[/code]. If defined, when this extension is used to handle images, and the images are saved to a separate file, the image bytes will be copied to a file with this extension. If this is set, there should be a [ResourceImporter] class able to import the file. If not defined or empty, Godot will save the image into a PNG file.
Part of the export process. This method is run after [method _convert_scene_node] and before [method _export_node].
Returns an array of the image formats that can be saved/exported by this extension. This extension will only be selected as the image exporter if the [GLTFDocument]'s [member GLTFDocument.image_format] is in this array. If this [GLTFDocumentExtension] is selected as the image exporter, one of the [method _save_image_at_path] or [method _serialize_image_to_bytes] methods will run next, otherwise [method _export_node] will run next. If the format name contains [code]"Lossy"[/code], the lossy quality slider will be displayed.
Returns an array of the glTF extensions supported by this GLTFDocumentExtension class. This is used to validate if a glTF file with required extensions can be loaded.
Part of the import process. This method is run after [method _import_post_parse] and before [method _generate_scene_node].
This method can be used to modify or read from any of the processed data structures, before generating the nodes and then running the final per-node import step.
The return value is used to determine if this [GLTFDocumentExtension] instance should be used for importing a given glTF file. If [constant OK], the import will use this [GLTFDocumentExtension] instance. If not overridden, [constant OK] is returned.
Runs when parsing the node extensions of a GLTFNode. This method can be used to process the extension JSON data into a format that can be used by [method _generate_scene_node]. The return value should be a member of the [enum Error] enum.
This method is run when saving images separately from the glTF file. When images are embedded, [method _serialize_image_to_bytes] runs instead. Note that these methods only run when this [GLTFDocumentExtension] is selected as the image exporter.
This method is run when embedding images in the glTF file. When images are saved separately, [method _save_image_at_path] runs instead. Note that these methods only run when this [GLTFDocumentExtension] is selected as the image exporter.
This method must set the image MIME type in the [param image_dict] with the [code]"mimeType"[/code] key. For example, for a PNG image, it would be set to [code]"image/png"[/code]. The return value must be a [PackedByteArray] containing the image data.
Part of the export process. This method is run after [method _save_image_at_path] or [method _serialize_image_to_bytes], and before [method _export_node]. Note that this method only runs when this [GLTFDocumentExtension] is selected as the image exporter.
This method can be used to set up the extensions for the texture JSON by editing [param texture_json]. The extension must also be added as used extension with [method GLTFState.add_used_extension], be sure to set [code]required[/code] to [code]true[/code] if you are not providing a fallback.
