Houdini 20.5 Unreal

Coordinate Systems

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Houdini and Unreal use two different coordinate systems.

Houdini (left) and Unreal (right) coordinate systems

Axis conversion

Houdini Engine for Unreal plugins converts all the transforms and geometries (positons, normals, etc.) from Houdini to Unreal’s coordinate system.

For example, an asset located at (0, 10, 5) in Houdini will be located at (0, 500, 1000) in Unreal. Despite the different values, both the unreal asset and Houdini assets will be at the same location.

Vector3 Parameters

Vector3 parameters such as Integer or Float are identified and displayed using Unreal’s XYZ coordinates. However, other parameters do not.

This means a Y-position parameter in Houdini controls the Z-position in Unreal’s coordinates system.

To prevent Vector3 parameter from switching its Y and Z in Unreal, you need to set the parameter tags.

  • Set the Tag Name to hengine_noswap and the Tag Value to 1.

See Parameter tags for more information.

This results in Houdini and Unreal having the same XYZ and orientation values but different visual location and orientation.

Example: (left) default import settings from Houdini Engine. (right) add the Vector3 parameter to prevent the axis from switching.

Unreal

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