Boards can be of arbitrary shape, size, and contour, and have arbitrary cutouts and holes.  Multiple boards can exist in a single layout to accommodate the preview of panelized board sets.  Each layer of substrate (core and prepreg) is depicted and can be individually enabled for view.  The layer stackup manager defines the number and individual thickness of each layer.

Internal planes are rendered as they will appear in the fabricated board and can be checked for proper thermals, non connects, split plane definitions and board edge clearances.

Solder reflow is simulated.  Note the two tented vias which are not plated in solder.

Verify proper solder mask cutouts and paste mask coverage. 

Highlighting (shown here in yellow) can be enabled which tracks any feature which has been selected in the PCB layout. 

Height restriction areas can be defined in the layout using Altium's standard "Room" objects and assigned a height.  These areas can be displayed in the 3D view as translucent surfaces.   Any  component which impinges upon a height restriction area is (optionally) highlighted in red.  Any number of (possibly overlapping) height restriction areas may be defined on one or both sides of the board.