Give Reference Point:
Indicate a point on the drawing that can be used as a reference point for the level. This should be a common point appearing in each floor plan or level such as the corner of an external structural wall. The prompt now reads.
Give First Point:
Select one corner of a selection box enclosing the floor area to be included in the level.
Give Second Point:
Select the opposite corner of a selection box enclosing the floor area to be included in the level.
The level is now defined and a dotted box denoting this is drawn on a layer called 'levels'.
The following example shows how to define the Levels for a two story building.
Select the Levels command and make sure the values match the dialog box above, then click OK.
The picture below shows the ground floor and first floor of the building. First we will define the Level detail of the ground floor so click on the external end point of the wall at P1, this is the reference point. The box that encloses this level is defined by clicking approximately at P2 & P3. The level box will be drawn.
Now that the levels are correctly defined the 3D Viewer will be able to 'stack' the floors so that the building displays correctly.