there are several ways to "isolate" the 3d-geometry in eM-Plant.
first of all, it is important to know, that a defined 3d-object has a hierarchical structure !
The hierarchical structure can be displayed by moving the mousecursor onto the 3d-browser,pressing the right mouse-button and toggling (on/off)
If you step into the sublevels, only the sublevel geometry is displayed.
So you just have to create a new (3d-) object, step into the apropriate object-level and drag the wrl-file onto this level.
another possiblity:
if you´ve already dragged the geometry into your mainlayout, you can create a new 3d-eMplant-object by selecting the geometry, pressing the right mouse-button and creating a new viewerobject.
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Der Simulator