Houdini 22.0 Import and export

Import and export glTF

How to import and export glTF files to and from Houdini.

On this page

glTF Specification

Houdini’s glTF importers and exporters adhere to the glTF 2.0 specification.

Nodes

Note

As of Houdini 22.0, glTF support in Houdini is built on a new underlying GLTF library. Because the process of migrating nodes to the new GLTF library is still on-going, the list of nodes and the glTF feature support chart below will contain both the original GLTF nodes built on the Houdini GLTF 1.0 library and the new GLTF nodes built on the Houdini GLTF 2.0 library.

Use the following Houdini GLTF 1.0 nodes to import or export glTF data:

OBJ GLTF Hierarchy node

Imports a .gltf or .glb file as a hierarchy of Object nodes.

SOP GLTF node

Imports geometry from a .gltf or .glb file into the SOP level.

ROP SOP GLTF node

Exports geometry at the SOP-level to a .gltf or .glb file.

ROP SOP GLTF Character Output node

Exports a rigged character at the SOP-level to a .gltf or .glb file.

ROP GLTF Character node

Exports a rigged character at the SOP-level (KineFX) to a .gltf or .glb file.

ROP GLTF node

Exports a scene, an Object, or a SOP to a .gltf or .glb file.

Use the following Houdini GLTF 2.0 nodes to import or export glTF data:

SOP GLTF 2.0 node

Imports geometry from a .gltf or .glb file into a SOP network.

SOP GLTF Character Import node

Imports a rigged character from a .gltf or .glb file into SOPs as a KineFX character.

SOP GLTF Skin Import node

Imports a glTF skin from a .gltf or .glb file into a SOP network as skin geometry ready to be used with KineFX.

SOP GLTF Animation Import node

Imports a glTF animation that specifically targets a glTF skeleton/joint hierarchy from a .gltf or .glb file into a SOP network as an animation that is ready to be used with KineFX.

ROP SOP GLTF 2.0 node

Exports geometry from a SOP network to a .gltf or .glb file.

ROP GLTF 2.0 node

Exports a an Object network or a SOP node to a .gltf or .glb file.

Supported glTF Features

The follow table can be referenced to determine which features of the glTF specification are supported by which Houdini GLTF nodes.

Exporters Importers
glTF Property or Extension ROP GLTF ROP GLTF 2.0 SOP GLTF Character Output SOP GLTF SOP GLTF 2.0 SOP GLTF Character Import OBJ GLTF Hierarchy
Scene
Node
Mesh
Mesh Primitive (Points)
Mesh Primitive (Lines)
Mesh Primitive (Triangles)
Camera
Skin
Morph Target
Animation (Transform Target)
Animation (Weight Target)
Material
Texture
KHR_draco_mesh_compression Extension
KHR_lights_punctual Extension

Materials

Materials are imported and exported different ways depending on the GLTF node.

  1. GLTF Hierarchy imports materials by creating Principled Shader nodes in a Material Network and setting the values of the parameters.

  2. SOP GLTF 2.0 imports glTF materials by using the material_overrides attribute. A SOP node cannot create other nodes during its cook, which makes this node limited to importing materials using the material_override attribute. It’s still flexible because it allows every mesh primitive that is imported to have its own material assignment. This is possible because the material_overrides attribute is a primitive attribute. If you want to persist an imported material in the Houdini scene, SOP GLTF 2.0 has the ability to bake materials to a material network.

  3. SOP GLTF Character Input imports materials in the same manner as SOP GLTF 2.0 but does not have the option to bake materials. If you need to bake materials out, use the SOP GLTF 2.0 node.

  4. ROP GLTF 2.0 exports any materials assigned to geometry via the shop_materialpath attribute that the exporter discovers in the course of exporting the scene.

Supported Material Features

The following table can be referenced to determine which glTF features and extensions are supported by each of the shader types that are supported by Houdini GLTF.

Note

This chart only applies to nodes built with Houdini GLTF 2.0.

glTF Property or Extension

Supported with Viewport Shader

Supported with Principled Shader

Supported with Mtlx Gltf Material Shader

baseColorFactor (PBR Metallic Roughness)

baseColorTexture (PBR Metallic Roughness)

metallicFactor (PBR Metallic Roughness)

roughnessFactor (PBR Metallic Roughness)

metallicRoughnessTexture (PBR Metallic Roughness)

normalTexture

occlusionTexture

emissiveTexture

emissiveFactor

alphaMode

alphaCutoff

doubleSided

KHR_materials_emissive_strength

KHR_materials_ior

KHR_materials_specular

KHR_materials_transmission

Controlling Alpha Blend Export on Principled Shader

When exporting a Principled Shader material, the alpha blend mode in the exported material can only be defined by adding extra render properties to your Principled Shader node.

  1. Select the Principled Shader VOP node in your material.

  2. In the parameter editor, open the Gear menu and choose Edit Rendering Parameters.

  3. In the Render Properties tree, find Material Options, then glTF folder.

  4. Drag the glTF Alpha Mode and glTF Alpha Cutoff properties from the glTF folder into the node’s Existing Parameters tree.

  5. Click Apply.

You can then use the newly added parameters to control the alpha blend mode and alpha cutoff of the exported glTF material.

To...Do this

Import a glTF scene with GLTF Hierarchy

In the main menu, choose File ▸ Import ▸ GLTF Scene.

Export the current scene (or a subset of objects) as a GLTF file

In the main menu, choose File ▸ Export ▸ GLTF.

Import and export