Design Options allow you to add new model objects to represent an alternative design for a part of a project.
By default all model objects are in an option called Main Model.
When you create a new Design Option all objects in Main Model will be visible.
You then add new objects to the new option.
But you can not hide objects in a design option.
To do that you have to move the objects you don't want from the Main Model into another option.
Usually you move them to an option that is labeled as the primary option. Objects in an option of this type will display along with Main Model objects by default, and represent 'business as usual'.
So when creating a new option you need to create a minimum of 2 options, a primary one to hold objects you don't want to see, and the actual option holding objects you do want to see.
To help manage this Revit has Option Sets that gather options together. Typically an alternative design will consist of a Option Set containing 2 options, the primary option and actual option.
CREATE OPTIONS
From Manage tab, Design Options tile select Design Options button.
Under heading Option Set hit the New button.
A new option set will be created called Option Set 1, with one option called Option 1 (primary).
Next select Option Set 1 and under heading Option Set hit the Rename button.
Give it a descriptive name that even a director would understand.
Then select Option 1 (primary) under heading Option hit the Rename button.
Also give it a descriptive name that a director would understand.
Now create the actual option by hitting the New button under Option heading.
Also rename this option.
Close the Design Options dialog.
SET OPTIONS UP
If you have already drawn objects you don't want to appear in your option (in this case 3 rooms), you will need to move them to the option set, and in to the primary option (2 rooms).
Select the objects you want to move, then from Manage tab, Design Options tile select Add to Set button.
A dialog will appear with Design Option sets in a drop down list under Add Selection to: heading, and under that a list of options in that design option set.
In this case untick 3 rooms as we DON'T want these objects in that option.
You will now find you can not select these walls as they are now in a design option. But you can see them because they are in the primary option. (you can actually select them by unticking Exclude Options in the status bar).
SWITCH BETWEEN OPTIONS
To work in options you need to tell Revit which option you want to work in.
There are 3 ways of doing this.
Pick the option you want from the drop down list in Manage tab, Design Options tile.
Pick the option you want from the drop down list in the status bar at bottom of the screen (best method).
Select Pick to Edit in Manage tab, Design Options tile, then select an object (if you hover your mouse over an object it will tell you which option it belongs to).
DRAWING IN OPTIONS
If we go to the 2 rooms (primary) option we see objects in the Main Model grayed out and can't be selected, and the walls we moved are black and can be edited:
If we go to the 3 rooms option the Main Model objects are there, but the walls we moved are not:
We can now draw in the objects we want for this option.
For more information on working with options refer to WORKING IN OPTIONS.
For information on how to create views showing particular design options refer to PRESENTING DESIGN OPTIONS.
For information on dealing with rooms in design options refer to ROOMS & DESIGN OPTIONS.