This tip from Dean Petersen will help you view highly complex surfaces in AutoCAD Civil 3D.
"The Level of Detail function was built into Civil 3D 2012, and I did not think too much of it back then as all it did was change the number of contours displayed on a surface in the drawing.
"Recently, however, we had a problem with a surface of 8 million points. Civil 3D 2014 would handle the surface just fine, but the 3D Object Viewer ran so slowly that it was almost unusable. We discovered that the Level of Detail function has now been expanded to reduce the number of triangles displayed in the Object Viewer as you zoom in and out as well, and now our surface is checkable against the rest of the model again without the need to apply boundaries to cut its size down. That made us all happy.
"The Level of Detail toggle can be found in the Ribbon View Tab / Views Panel drop-down menu."
Notes from Cadalyst tip reviewer Brian Benton: Civil 3D is a data hog, especially when it comes to surfaces — they will test the abilities of your computer. The Level of Detail setting was introduced to help ease your computer's rendering pains. It doesn't change the data, just how much of the details will be shown on the screen. Reducing the amount of detail shown means less work for your computer and video processor.