@Chris_Young_Kim note too that the Slicer code is fully available to inspection (and run–time introspection) so there’s no reason you can’t find the exact settings used in Slicer and replicate them in other VTK context. It would be great if you could report back the “minimum viable code” to make volume renderings look the way you want. It would be a nice contribution to the community if you could provide examples of what works for you in the end.
BTW, if you learn how to do additional interesting volume rendering effects we’d all love to learn what works for you.