To show only the marqueed element(s) in 3D, use the View > Elements in 3D View > Show Selection/Marquee in 3D command.
The caption of the 3D Window will include the “Marquee” mention.
For more information on defining a marquee area, see Marquee Area.
If your plan includes both explicitly selected elements and a marquee selection, this command will disregard the marquee and show only the explicitly selected elements.
Marquee Effect: By default, the elements inside the Marquee will be displayed and they will be cropped to the marquee area. However, you can adjust the Marquee effect to show the elements outside the marquee instead of those inside: use the Marquee Effect controls in View > Elements in 3D View > Filter and Cut Elements in 3D, and choose the Outside Marquee radio button.
See Filter and Cut Elements in 3D Dialog Box.
To show the entirety of elements that fall partly inside the marquee - without cropping them - uncheck the Trim Elements to Marquee checkbox (also under Marquee Effect, in View > Elements in 3D View > Filter and Cut Elements in 3D).
Elements in a Marqueed 3D Window
If you create an element in the 3D Window which is delimited by a marquee, the new element will only appear in the 3D Window if you draw it inside the marquee area.
If you place a new element outside the boundaries of a Marquee-based 3D view, or drag an existing element outside the Marquee boundaries, that element will disappear immediately from the 3D Window.
When you go to the Floor Plan, however, you will see the elements. Change your marquee area (or remove it) and return to the 3D Window to check it.
If you select one or more elements in a trimmed 3D view, resulting from either a Marquee area or a 3D Cutaway, some elements will be only partially visible, but selection dots of the whole element will be displayed and all the nodes and edges can be found with the cursor.
If edited, a temporary ghosted image of the whole element will be visible.
