Performance issue with instances if original shape not attached

[harokyang]

attach original shape = OK
attach original shape with instances = OK
attach instances without original shape attached = ultra slow speed

[yozhijk]

Could you please attach our hardware spec?

[harokyang]

You mean "your" or "our"?

Here is my hardware
i5-7500 3.4GHz
16GB RAM
GTX 1080Ti 11GB VRAM

I'm working on some indoor scenes with hundred of unique objects and thousand instances of them

Case 1:
Load all objects as Shapes and only use them as instance references, none of them are attached to the Scene
Create thousand of Instances from the referenced Shapes, attached them to the Scene
During the rendering, the GUI shows Unique triangles: 0, Number of instances: xxxx

Result: I can hardly move the camera

Case 2:
Same as Case 1 but all referenced Shapes are attached to the Scene

Result: Everything works as expected

[harokyang]

running on Windows 10 Pro 64bit
compiled with Visual Studio 2017