Using Boolean operations in Rhino
|The Boolean tool in Rhino is ideal for constructing complex objects. This tutorial will introduce the functions of Boolean operations in Rhino and highlight a few problems to watch out for.|
Introduction to Boolean Operations
In order to perform the Boolean command, select two intersecting objects. Use the menu buttons from the Toolbar or use the Boolean command. There are four methods to Boolean objects in Rhino.
- Union: the two objects will be joined into one single object.
- Difference: the object that is selected first will be cut by the other object. What remains is the uncut portion of the first object.
- Intersection: only the intersection portions of the two objects will remain.
- Split: the two objects will be separated where they intersect, leaving behind three separate objects.
Use the "Boolean2Objects" command to quickly cycle through these four options by left clicking the mouse. Press Enter to select the operation you need.
Why Use Boolean Operations
Boolean operations essentially automates a set of commands that can be performed manually to achieve the desired result, making it faster and easier. However, because the Boolean command does not always work, it is important to remember that the Trim, Delete, EdgeSrf, and Join commands can be used to do the same job.
When Boolean Operations Fail
A common reason for an failed Boolean operation is selecting an object with shared surfaces. If one of the objects shares a surface with another object, or if there are duplicate surfaces in the model, the operation will fail. There are two ways to determine if this is the problem.
Select the object in question with a Left-Right Bounding Box (click and drag a selection box from the bottom left corner to the top right corner), which will selects all the surfaces that make up that object. The Command History Window (right above the command box) will specify how many surfaces or objects are selected. If more than one object is selected, then the object has a shared or duplicate surface. Delete the unwanted surfaces and try the Boolean operation again.
Or, click on Edit --> Select Objects --> Select Surfaces. All surfaces in unlocked layers will be highlighted in the model. Delete these surfaces so that only the objects remain, and try the Boolean operation again.
Troubleshooting: Boolean Difference
When using Boolean Difference to cut an object, sometimes the portion that remains is the portion that you do not want. This can be a result of the direction of the cutting surface (the object that is selected second). To change the object's direction, select the object and use the "Dir" command. Enter "F" to flip the direction of the object, and then try to Boolean Difference again.
Troubleshooting: Unjoined Objects
Another common reason why Boolean operations fail is because there may be a gap in one more or of the objects. Both objects need to be closed objects in order for the operation to work. If an object was created by manually trimming, adding, and deleting surfaces, remember to use the Join command to close the object.
To check if there are any open edges in the model, use the "ShowEdges" command. In the Edge Analysis option panel, select "Naked Edges" to highlight where there are gaps in the object. Select the adjacent surfaces and use "Join" to close the object. Then, try the Boolean operation again.