Is there convenient way to render a fixed, user-defined volume (e.g. 50x50x50) centered on a marker? This will allows the user to compare 3D rendering of multiple samples in a consistent manner.

Thanks,
Jichao

that is the local 3d viewer. you can right click anywhere directly in an image (in the 3d viewer), or first define a marker somewhere of your interest (from either the tri-view main window or the global/local 3d viewer), and then select from the pop-up menu to open a local 3d viewer or "zoom in".

you can also precisely compare two 3d viewers from the same orientation. The buttons are at the right-bottom side of a 3d viewer.