How to use A23D 3D Models in Houdini

This guide explains how to import 3D models downloaded from A23D into Houdini (Houdini 19.5 / 20 / 20.5+) for use in animation, VFX, simulation, and visualization projects.

1. Download and Extract the Model

  1. Sign in to your A23D account.
  2. Browse to the asset you wish to use.
  3. In the Software dropdown on the asset page, select Houdini.
  • A23D automatically delivers the model in the format best suited to Houdini (.fbx) - no manual format selection required. Keep the .fbx file and texture files together because the model references its dependent files.
  1. Click Download and save the .zip to a known location on your computer.
  2. Extract (unzip) the archive to access the delivered model package.

2. Import the A23D Model

Method A - Houdini Package Import (Object Level)

  1. Launch Houdini and open your scene.
  2. In the top menu, go to File > Import > Filmbox FBX....
  3. Navigate to the extracted model file and click Open.
  4. In the Import FBX dialog:
  • Enable Import Materials to bring in the embedded materials.
  • Set the Convert Units option if your scene units differ from the FBX's meters.
  • Click Accept.
  1. Houdini imports the model into a subnetwork at the Object (OBJ) level. Inside, you'll find geometry and a materials network.
  1. In a Stage (LOP) context, drop down a File or Reference LOP node.
  2. Set its file path to the model file included in the A23D Houdini package, or to a USD file if your pipeline has converted the asset to USD.
  3. The model loads as a USD prim ready for further USD-based shading and lighting.

3. Materials and Textures

A23D 3D models come with PBR material data. When you import the Houdini package through Houdini's FBX importer, Houdini creates Principled Shader materials and assigns them to the geometry where the material data is resolved. For Karma rendering in Solaris, you may want to rebuild or convert these materials as MaterialX shaders - SideFX recommends MaterialX as the modern shading workflow, and Karma XPU only supports MaterialX.

To inspect or modify materials:

  1. Dive into the imported subnetwork.
  2. Navigate to the /mat (material) network.
  3. Edit the Principled Shader parameters or the MtlX Standard Surface node connected to the MtlX PBR Texture Set VOP:
  • Base Color (Albedo)
  • Roughness
  • Metallic
  • Normal
  • Displacement

Changes update live in the Karma / Mantra / Redshift viewport.

4. Position and Scale

Use a Transform SOP or the object's transform parameters to position and scale the imported model. A23D models are authored in meters - match your scene's lengthunit setting.

Additional Resources

For more detailed information on importing models in Houdini, refer to SideFX's official documentation:
Importing FBX files - Houdini Help
Karma User Guide - Materials

Need some help?

Contact our team at support@a23d.co