A boolean object combines two other objects by performing a Boolean operation on them. For geometry, the Boolean operations are:
The two original objects are called the operands. The first is designated as operand A, the second as operand B.
You create booleans in the Create control panel. The Geometry button must be active and you must choose Compound Objects from the object category dropdown list. The Boolean button is enabled if an object is selected.
When you pick operand B, you designate it as a Reference, Move (the object itself), Copy, or Instance, according to the radio button selection in the Pick Boolean rollout for boolean objects.
This choice specifies how the boolean object uses the object B geometry. Base your selection on how you want to use the scene geometry after you create the boolean.
Copy: The boolean object uses a copy of the operand B object. The original B object is unchanged.
Use Copy when you want to reuse the operand B geometry for other purposes in the scene.
Move: The boolean object uses the operand B object itself. The original B object disappears and is no longer available after the boolean is created.
Use Move if you've created the operand B geometry only to create a boolean, and have no other use for it.
Instance: The boolean object uses an instance of the operand B object. If you later change the original B object, the boolean object also changes; and if you change the boolean object's B operand, the original B object changes.
Use Instance to synchronize animation of the boolean object with animated changes to the original B object.
Reference: The boolean object uses a reference to the operand B object. If you later change the original B object, the boolean object changes as well; but if you change the boolean object's B operand, the original B object does not change.
Object B geometry becomes part of the boolean object regardless of which copy method you use.
Operands list field: Displays the current operands
Operand A Name: Edit this field to change the name of Operand A
Opernad B Name: Edit this field to change the name of Operand B
Extract Operand: Extracts a copy of the selected operand. Simply choose one of the operands in the list window to enable the button, and then click the Extract Operand button to make a copy or an instance of the original operand.
Note: This button is only enabled in the Modify panel. You cannot extract an operand while in the Create panel.
Union. When selected, the boolean object contains the volume of both original objects. The intersecting or overlapping portion of the geometry is removed.
Intersection. When selected, the boolean object contains only the volume that was common to both original objects (in other words, where they overlapped).
Subtraction (or difference). When selected, the boolean object contains the volume of one original object with the intersection volume subtracted from it.
Boolean objects: union,intersection and subtraction
Visualizing the result of a boolean can be tricky, especially if you want to modify or animate it. The Display area in the boolean Parameters rollout helps you visualize how the boolean is put together.
The display controls have no effect until you've created the boolean.
Result: Choose to view the result of the Boolean operation -- that is, the boolean object itself.
Because you usually create boolean objects from overlapping objects, if the B object isn't removed (you don't use the Move option), it often obstructs your view of the completed boolean, or vice versa. You can also move the boolean or the B object to better see the result.
Operands: Choose to view the operands instead of the boolean result.
Show Hidden Ops: Check to view the "hidden" operands in shaded viewports.
Operand geometry remains part of the compound boolean object, although it isn't visible or renderable. When this parameter is checked, 3D Studio MAX displays the operand geometry as wireframes in shaded viewports.
This parameter has no effect if the viewport is not shaded, or if operands are displayed.
Tip: When operands are hard to see in a viewport, you can use the Operand list to select one or the other. Click the name of the A or B operand to select it.
Displaying operands or result
Hidden operands
By default, booleans are updated whenever you change the operands. When your scene contains a complicated, animated boolean -- or more than one -- this can impede performance. The update parameters provide some alternate methods that can help performance.
Always: Updates booleans immediately whenever you change an operand, including the original object of an instanced or referenced B operand. This is the default behavior.
When Selected: Updates booleans only when you select them.
If your scene contains multiple boolean objects that you need to update, select all objects to update the booleans, then select none.
When Rendering: Updates booleans only when you render the scene. With this option, viewports won't show current geometry. If in doubt, update booleans manually.
Manually: Updates booleans when you click Update. The Update button is enabled only when Manually is the active option.
Update: Updates the boolean
Optimize Result: When checked, 3D Studio MAX removes co-planar faces when it updates boolean geometry. (The edge between co-planar faces can be visible in renderings.)
This object is operand A. Operand A becomes the boolean object; it loses its original type even if you don't perform a Boolean operation on it.
The name of operand A appears in the Operands list in the Parameters rollout.
These methods are described in the following topic.
3D Studio MAX performs the Boolean operation.
The operand objects remain as sub-objects of the boolean object. By modifying the creation parameters of the boolean's operand sub-objects, you can later change operand geometry to change or to animate the boolean result.
Note: Occasionally the boolean result can have face normals that point the wrong way. You can adjust normals by using the Normal or Edit Mesh modifiers. You can also use the Normal Align command.