Houdini Engine for Unreal
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Using FBX Files

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FBX (Filmbox) files are an interchange format commonly used in the industry. Even if using them will not involve Houdini Engine, this page is meant to give you some advices regarding import and export of FBX files between the Unreal Engine and Houdini.

Export from Houdini

There are several ways you can export data from Houdini to FBX files. You can either use the File > Export dialog, or the FBX render node.

When exporting from Houdini to Unreal, there is a couple of important things to remember:

  • The first and foremost, is to make sure the export is done with the 2016 SDK as it is the one currently supported by Unreal's FBX import pipeline. This can be done by selecting FBX|FBX201600 in the Version combo in the exporter dialog or ROP node parameters. Exporting with another SDK version might give you corrupted results or incompatibilities.
  • If you want to export Blend Shapes to Morph Targets in UE4, your asset's network needs to be "FBX Compatible". Please make sure that there is no nodes that modify the geometry after the blendshape nodes. Nulls, switches, caches, attributes, skin deform or merge nodes won't block the blend shapes from being exported, but nodes that alter the geometry, like a subdvide for example, will. You can also tell the exporter to Force Blend Shapes Export, this will make it ignore all the incompatible nodes.
  • Blendshape animations can be exported, but the shapes themselves can't be time dependant in Houdini, as this is not supported by FBX.
  • Exporting vertex animations will prevent blend shapes export, unless the Force Blend Shapes Export option is enabled.

Import into Unreal

Here are some advices when importing FBX files exported by Houdini into Unreal:

  • Because of the difference in length unit between Houdini (1 unit = 1m) and Unreal (1 unit = 1cm), make sure to always use a uniform scale of 100 in the FBX import dialog, or the resulting mesh in Unreal will be very small.
  • There is no need to take into account the difference in Coordinate Systems between Houdini and Unreal when importing FBX files created by Houdini, as the FBX exporter in Houdini has already taken care of this.