Yes, much to our chagrin, this is expected.
Within a Sketchup instance, the fastest way to copy geometry is to select, move, and then activate copy (Ctrl on Windows) just before committing.
Between two Sketchup instances, however, you cannot move geometry. So natively, you have to copy via memory.
And this often takes many minutes. One minute. Two minutes. Five. Ten. Fifteen. Twenty minutes, indeed. And counting. So, why is this?
Apparently, Sketchup forces lots of internal consistency checks when copying to memory. When creating new containers. When doing many other things. These checks are incredibly slow. From a programming point of view, Sketchup’s behaviour is most likely very badly optimized. There is either something sloppy about the internal database structure, or about how it is being processed, or about both.
We know this because other 3D modellers are much, much faster doing similar tasks. Both copying between instances and doing other editing of non-trivial geometry. Sketchup can do OK in terms of showing complex geometry. It’s editing that grinds it to a halt.
While we’re staring at Sketchup’s blank and irresponsive screen after a sizeable copy, no processor core is even near maxing out. So this process may be memory-bound. Its slowness does not matter when working with three cubes, for it escapes notice. As it did around twenty years ago.
However, when working with contemporary, real-life models, i.e. complex geometry, like you and I do, the recurring waiting times is a real pain.
All this would be bearable if it were not for the fact that other 3D modelers do perfectly fine without all this waiting time. Which proves this is unnecessary:
– Does it work on three cubes? Boy, let’s ship it!
The best explanation, I think, of why this still is so even twenty years after Sketchup’s conception, is that Trimble does not force its product managers to regularly solve pressing, real-life problems in complex Sketchup models.
Like you and must I do. Every day. When Trimble’s product managers have worked every day for a year or two having to solve pressing, real-life problems in complex Sketchup models, they will deal with the problem.
For all of Sketchup’s good aspects – and there are plenty – what you are pointing to is precisely Sketchup’s main weakness:
lack of performance when managing and editing complex geometry.
The solutions are all painful. Either:
Trimble decides to solve it in ernest. They get their hands dirty and start whacking at the core. Or
Users that need complex geometry go elsewhere. E.g. Blender is much faster. Or
We simply invent a time-machine that takes us back to 2001 when this was acceptable.