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Severe performance degradation of actor linked to large bounds scale in 4.25.

I’ve been working on a buoyancy system in 4.24, and recently decided some features in 4.25 would be worth pairing it with, so I decided to migrate the assets. After migration the performance was terrible. In order to handle a lot of buoyant objects, I calculate the buoyancy physics of distant objects in render targets, and move them via world position offset in their material, so I have to make their bounds scale really large.

In 4.25, if I keep the bounds scale at 1, the performance returns to normal, but I get constant pop in and out due to objects bounds moving off screen.

Anyone have any ideas how I might begin to track this down this issue? I haven’t done much CPU profiling, so suggestions are appreciated.

Normal Bounds

Large Bounds


Edit: figured it out. Wasn’t just in 4.25, the same thing happened when I migrated to another project in 4.24, and in a fresh project with new simple actors. If you add an actor that spawns a bunch of actors with big bounds scales to your level, for some reason you need to uncheck, then recheck “cast shadows” on the lights in your level to make performance return to normal.