3D viewport for After Effects - Diorama 3D by AnvilFx
Diorama 3D is a plugin made by AnvilFx (me). I'ts designed to make working with native AE 3D layers much less painful.
You can read all about the plugin on anvilfx.com/diorama-3d
There is a 7 Day free trial you can download on the website as well, and a launch discount which will last till the end of the month. The plugin isn't out on aescripts yet, but will be in a few weeks time.
For anyone with concerns about performance, it should have a minimal effect on performance. Diorama barely touches the render path. It reads the scene through AE's idle hook, so while AE is busy rendering, the plugin minds its own business. The only thing that touches the render path is an extra effect that comes with Diorama which automatically applies to all 3D layers with effects on them (which can be disabled), which is there to hand Diorama data about the layer its on, so it can be displayed correctly.
About AI: Unfortunately there is really no way for a single person to make a plugin like this without coding help from AI (at least not for me). However, that is all AI has assisted with. The website and UI for the plugin are both designed by me. All icons are either made by me or bought legitimately (apart form a couple placeholder SVGs that are yet to be replaced).