With our test computer (Pentium 4 from year 2004 and Windows XP), our software running with a standard lightshow (without 3D representation*) takes less than 5% of the processor time.
* the processor time for 3DView depends of your video card.
A powerful 3D video card should cover all the processor time required for 3DView.
If your computer just has a basic video chip (no 3D), 3DView might take 100% of your main processor time.