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ExportRuntime.md

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Runtime Export

You can export individual GameObjects or entire scenes to glTF™ files at runtime.

Include Required Shaders

To be able to export certain textures correctly, a couple of shaders are required. They are located at Runtime/Shader/Export. Make sure to include them all in your build.

The easiest way to include them is to add glTFExport.shadervariants to the list of Preloaded Shaders under Project Settings > Graphics > Shader Loading.

Export via Script

NOTE: The GLTFast.Export namespace can only be used if you reference both glTFast and glTFast.Export Assemblies in your Assembly Definition.

Here's a step-by-step guide to export a GameObject hierarchy/scene from script

  • Create an instance of GameObjectExport
  • Add content via AddScene
  • Two options for the final export
    • Call SaveToFileAndDispose to export a glTF to a file(s)
    • Call SaveToStreamAndDispose to export to a Stream

glTF export might create more than one file. For example the binary buffer is usually a separate .bin file and textures might be separate files as well.

[!code-cs simple-export]

After calling SaveToFileAndDispose the GameObjectExport instance becomes invalid. Do not re-use it.

Further, the export can be customized by passing ExportSettings, GameObjectExportSettings and injectables to GameObjectExport's constructor:

[!code-cs advanced-export]

NOTE: Exporting to a Stream currently only works for self-contained glTF-Binary files (where the binary buffer and all textures are included in the .glb file). Trying other export settings will fail.

Scene Origin

When adding GameObjects to a glTF scene, the resulting glTF root nodes' positions will be their original GameObjects' world position in the Unity scene. That might be undesirable (e.g. if the scene is far off the origin and thus not centered), so AddScene allows you to provide an inverse scene origin matrix that'll be applied to all root-level nodes.

Here's an example how to export a GameObject, discarding its transform:

[!code-cs local-transform]

Vertex Attribute Discarding

In certain cases glTFast discards mesh vertex attributes that are not used or required. This not only reduces the resulting glTF's file size, but in case of vertex colors, is necessary to preserve visual consistency.

This behavior might be undesirable, for example in authoring workflows where the resulting glTF will be further edited. In that case vertex attribute discarding can be disabled on a per-attribute basis by setting ExportSettings' PreservedVertexAttributes mask.

Examples of vertex attribute discarding:

  • Vertex colors, when the assigned material(s) do not use them.
  • Normals and tangents, when the assigned material is unlit and does not require them for shading.
  • When no material was assigned, a default fallback material will be assumed. This does not require tangents nor texture coordinates, hence those are discarded.

NOTE: Not all cases of potential discarding are covered at the moment (e.g. unused texture coordinates when no textures are assigned).

Draco Compression

Unity glTFast supports applying Google Draco™ 3D Data compression to meshes. This requires the Draco for Unity package to be installed.

[!code-cs draco-export]

Trademarks

Unity® is a registered trademark of Unity Technologies.

Khronos® is a registered trademark and glTF™ is a trademark of The Khronos Group Inc.

Draco™ is a trademark of Google LLC.