If you use File>>Save As with "Rectangular section" in the file type name (e.g. Rectangular section BMP), you will need to enter a rectangular window using the mouse or command line (speaking of command lines, watch the command line for hints about what to do next) and CC3 will save just that part of the display to your image file. If you use File>>Save As with "Bitmap file" in the name (e.g. BMP Bitmap File), then CC3 will save your whole drawing extents to an image file.