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Houdini to Unreal Heterogeneous VDB Pipeline

//Unreal Prerequisites for Houdini -

  • Scene positioned at 0,0,0 or close to 0,0,0 (world space)

  • Single animations on single layer or single actor, no multiple animations on multiple actors. If absolutely necessary, bake down animation 

  • Start Sequences from frame 1000 - gives time for sim preroll (Houdini does not like negative frames)

  • Scene cleanup (Disposing assets not needed in the level). Heavy scenes create problems when rendering heterogeneous volumes and cause glitches.

  • Preferably avoid use of blueprints, Blueprints are not recognized / interpreted by Houdini.

//Troubleshooting Unreal Scenes - 

  • Check if hardware ray tracing is on/off

  • Check if Nanite is on/off on terrain

  • Check compatibility of assets with Unreal Versions

  • Check if volumetric shadows is turned on/off for lights in Unreal

//Houdini to Unreal VDB Pipeline - (Example .hip download (Simulate at Origin))

  • Import models into Houdini with convert units checked on in filmbox FBX dialog box (Houdini will scale down the whole scene by 100 units)

  • Extract transform and rotation and simulate at origin, use match size in the end to reapply xform transformation

  • Export VDBs out of Houdini by multiplying sim cache by a factor of 100

  • Import into Unreal, input into VDB material and add it to a heterogenous volume

  • When importing into unreal, change values as follows - Rotation (90, 0, 0) and scale (1, -1, 1)

  • Attach heterogeneous volume to the actor to reapply lost xform transformation

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