Per Instance Custom Data and Hierarchical Instanced Static Meshes

Hi everyone,

I have a problem with using Hierarchical Instanced Static Meshes in situations where I need to make use of per instance custom data. I have 11 custom floats defined, but when I try setting them, it seems like the values don’t persist or even get set properly, and values flicker like crazy and seem to swap around to different instances. The problem does not occur with an Instanced Static Mesh.

This was apparently a known issue in 4.25, and I was told it was fixed in 4.26, but I just updated to 4.26.0 and the same problem is occurring. This bug is a show-stopper for me, because I am trying to render large crowds of characters and I absolutely must use per instance custom data to tweak their animations and behaviour on an instance-by-instance basis, and I also want to be able to render thousands of them, so I really need the LOD features that a HISM provides. Using an ISM means I have to either run really low poly characters (I want the camera to get up close to them as well so this is really undesirable), or suffer huge performance penalties when going over a thousand instances (I am trying to aim for 20k).

Does anyone know about this bug, and how it can be fixed? I am happy to switch to a source build of the engine if anyone has a permanent fix for it, though I am hoping this can be resolved in the binary version of the engine too.