Use the Show Hidden Lines tool and view parameters to control hidden lines in model views.
This video demonstrates the following:
When you have one object positioned in front of another object in a view, you can use hidden lines to illustrate their relationship. Hidden lines show the edges of the object that are obscured behind another object. In this example, the edges of the wall that's obscured by the building are set to display as hidden lines in both the 3D and section views.
There are 3 ways to display hidden lines in a view. The first way is to display hidden lines one element at a time with the Show Hidden Lines tool. On the View tab, select Show Hidden Lines. Next, select the element in front, and then select the element behind to show its hidden lines. Select each obscuring element individually to show hidden lines. Use the Remove Hidden Lines tool to reset the elements.
The second way to show hidden lines in a view is by using the Hidden Lines setting for the view in conjunction with the Discipline setting for the view. To do this, set the Show Hidden Lines parameter for the view to By Discipline. Now, when you change the discipline of the view, elements will show hidden lines based on the categories of the elements.
For example, when the discipline is set to Structural, the interior hidden lines of the framing members are shown. When the discipline is set to Mechanical, the hidden lines of the duct elements in the view are shown.
The third way to display hidden lines is by using the Show Hidden Lines view parameter. Set this parameter to All on the Properties palette, and all of the hidden lines in the view are displayed. You can use this setting to display hidden lines that are part of one element, or to display hidden lines of an opening in an element. Conversely, if you set the parameter to None, hidden lines will never be displayed in the view.
With hidden lines displayed in a view, you can use the visibility and graphics overrides to control the appearance of hidden lines. For MEP elements, use the Mechanical Settings dialog to control the appearance of hidden lines. Set hidden line values in a view template to quickly apply hidden lines settings to multiple views.
Use these techniques to control the hidden lines in your views and present your projects effectively.