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