Repopulate float16

Repopulate (2.1.8.51092) is really picky about float16.

rle_channel.get_accessor: Could not access channel “Density”, because the requested type, float32 is incompatible with the channel type, float16.

It also complains if the Position is float16, but that’s pushing it a bit I know.

Oh, density at float64 is also broken.

Thanks for reporting the problem.

I’ll fix it for the next build.