In this lesson, you will use the subtraction Boolean operation to add an open atrium in front of the entrance to the building.

Set up the lesson:

• Continue working from the previous lesson.

Add an opening to the building entrance:

1. On the Create panel, click (Geometry), then on the Object Type rollout, click Box.

   This box will be used in a subtraction operation to create an opening for the left and right sides of the building.

2. Activate the Top view, drag to create a box as shown in the following illustration, with the upper and lower ends of the box protruding from the top and bottom sides of the Tower object. Exact dimensions are not important at this point.
   
3. On the Parameters rollout, set the dimensions of the box as follows:
   • Length=50.0m
   • Width=18.0m
   • Height=36.0m
4. Click (Align), then select the Tower object to display the Align Selection dialog.
5. In the Align Position group, turn on X Position and Y Position, then choose Center in both the Current Object and Target Object groups. Click OK.

   This aligns the box you just created to the center of the Tower object.

   Next, you need to create a second box that will be used in a subtraction operation to create an opening for the front of the building.

6. On the Create panel, click (Geometry), then on the Object Type rollout, click Box.
7. Activate the Top view, drag to create a box as shown in the following illustration, with the ends of the box protruding from the left and right sides of the Tower object.
   
8. Set the dimensions of the box as follows:
   • Length = 18.0m
   • Width = 41.0m
   • Height = 36.0m
9. Click (Align), then click the Tower object.
10. On the Align Selection dialog Align Position group, turn on X Position and Y Position, then choose Center in both the Current Object and Target Object groups. Click OK.

    This aligns the box you just created to the center of the tower.

    Next, you need to align the right side of the new box with the right side of the first box object, to create a back wall for the model.

11. Click (Align) once again, then click the Box001 object you created in step 2.
12. In the Align Selection dialog Align Position group, turn off Y Position so only X Position is on, then choose Maximum in both the Current Object and Target Object groups. Click OK.

    This aligns the box to the right-most edge of the first box object.

    
    

Subtract the geometry from the tower:

1. Select the Tower object and in the Modify panel Parameters rollout Operation group, choose Subtraction.
2. On the Pick Boolean rollout, click the Start Picking button, then click the two boxes you created in the previous procedure. The subtraction operation creates the gap for the entry area.
   
3. Click the Start Picking button again to turn it off.

Save your work:

• Save the scene as my_building2_atrium.max.