I am developing a 3DObject plugin to complement the great new 3DShape recently released into C3 stable. 3DObject can import 3D models in the obj/mtl/png format. I intend for the final version to be simple and well integrated into C3 (for instance, behaviors like 8 dir, drag and drop work, for controlling X,Y location of the 3DObject work now.) Low poly models work better in terms of performance.
The current version is in Alpha and still has lots of rough edges (e.g. the 3DObject shows up in the editor as placeholder sprite, only at runtime is the 3D model rendered.)
If you know a bit about 3D models and can work with Alpha (early release) SW, please try it out and give feedback or show what you have done with it. The itch page describes some of the process and limitations, it also describes possible features to add in the future. Below are some examples (example project included.) 3D Animations are not supported, but may come later after release of a stable version w/o animations.
Try it here: kindeyegames.itch.io/c3-3dobject-alpha
X,Y,Z rotations, integrate w/ other C3 objects (e.g. rotating sprite)
Using 8 dir on sprite to control 3DObject
Compatible w/ obj/mtl/png files generated by KenShape