So if I understand correctly:
-> Having xxx Object3D's will result in xxx draw calls for the Object3D's.
-> Having xxx Object3D's merged into 1 Object3D will result in just 1 draw call.
Isn't it possible for jPCT to automatically "merge" certain Object3D's? Not real merging into one Object3D, but just to reduce draw calls. (So I guess geometry-wise merging only)
I don't know if this will increase performance, since I'm not sure if merging itself is cheap performance-wise.
Another thing that might make this idea not work is the individual settings that are possible for Object3D's like different shaders. I don't think merged geometry could work with Object3D's with different shaders for instance.
But okay, for the Object3D's that share most settings, could those be merged geometry-wise?
Well a developer can instead just merge them immediately too to one Object3D, but at the cost of having control over the Object3D's it originally consisted of.