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EXTRAS.md

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Extras

AssetKit preserves source-format metadata that it does not need to interpret directly.

  • COLLADA: <extra>
  • glTF: extras and preserved extensions payloads

Use ak_extra() to read it:

AkTree *extra;

extra = ak_extra(object);
if (extra) {
  /* Walk extra->chld, node->next and node->attribs. */
}

Use ak_extra_set() when custom loader code wants to attach metadata:

ak_extra_set(object, extraTree);

The returned AkTree is owned by the document heap. Do not free it directly.

COLLADA

Older AssetKit code stored COLLADA <extra> data directly on struct fields such as node->extra, mesh->extra, geom->extra or material->extra. Those fields still work. New code should prefer ak_extra(object) so the same path works for COLLADA and glTF.

glTF

glTF metadata is stored under a root tree named extra:

extra
  extensions
    KHR_example_extension
      enabled   type=value val=true
  extras
    author     type=value val=...

Each glTF tree node has a type attribute:

  • object
  • array
  • value
  • null
  • unknown

Array items are repeated child nodes named item and preserve source order.

Typed AssetKit fields are still preferred for extensions AssetKit understands, for example material variants or Gaussian splat metadata. ak_extra() is for metadata, vendor payloads, debug payloads, and extension data that higher-level tools may want to inspect.

More detail: docs/source/extras.rst