TSR ghosting with spline mesh

My game uses a series of spline meshes to render a character (a snake). The positions and tangents of the spline meshes are updated every frame in BP.

In UE5 TSR, the moving spline meshes have a lot of messy ghosting, including quite an obvious dithered trail that lasts a few frames and looks awful. (TSR looks great in general, it’s just the spline meshes.) I assume this is because the spline mesh components aren’t updating their motion vectors.

The spline mesh components have their mobility set to Moveable. The components themselves aren’t actually moving, just the start and end points of the splines. If I move the whole component instead of moving the start point, the ghosting goes away, which confirms the assumption, I think. (Unfortunately, moving the whole components also creates some lighting issues and makes the snake look segmented, so that’s not a useful workaround.)

I think this is similar to how WPO materials don’t update their motion vectors by default, but there is a setting available to fix that. Not so for spline meshes. Similarly, using “r.BasePassForceOutputsVelocity 1” doesn’t help either. The engine just doesn’t consider the spline mesh to have moved.

In summary, it seems like updating the spline of a spline mesh doesn’t update the mesh’s motion vectors. Does anyone know a way to fix this?

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I submitted a bug report for this. I’ll update if it’s accepted.

What’s the ID of your bug report? I have the same issue with cable components.

Just seen this. Sorry - I can’t find the report. I could’ve sworn I posted it, but maybe I made a mistake. (I trawled through all of the tickets for May 22 and can’t see it.)

For what it’s worth, I never solved this and just abandonned TSR for that project.