Intersect Faces in SketchUp is a powerful command that creates new edges where two or more faces overlap or cross each other within your model. This function is essential for accurately combining, subtracting, or trimming 3D geometry, allowing you to create complex shapes and detailed models. It is important to note that Intersect Faces only generates edges, not new faces, along the lines where the surfaces meet.
Understanding How Intersect Faces Works
At its core, Intersect Faces analyzes selected geometry (or the entire model) and identifies all points where individual faces pass through one another. Once these intersections are detected, SketchUp automatically draws new edges precisely along these intersecting lines. These new edges then allow you to delete unwanted portions of the geometry, creating a clean, unified shape.
Key Characteristics:
- Edge Creation: Its primary function is to draw new edges where surfaces cross. No new faces are automatically generated.
- Context-Sensitive: The behavior of Intersect Faces is heavily influenced by the current editing context.
- If you're working directly on raw geometry, the edges are placed on those faces.
- If you've opened a group or component for editing before running Intersect Faces, the new edges will be placed on the faces inside that specific object. This is crucial for maintaining model organization and preventing sticky geometry.
Why Use Intersect Faces?
Intersect Faces is indispensable for several common modeling tasks, enabling precision and efficiency that would be difficult or impossible with simpler tools.
- Creating Complex Joints: Perfect for joinery in woodworking, such as mortise and tenon or dovetail joints.
- Boolean-like Operations: While SketchUp doesn't have dedicated Boolean tools like some other CAD software in its free version, Intersect Faces, combined with the Push/Pull tool, effectively allows you to perform union, subtract, and intersect operations.
- Modeling Intersecting Objects: When you have objects like pipes crossing, roof planes meeting, or furniture components interlocking, Intersect Faces provides the necessary edges to clean up their connections.
- Making Openings: Cutting precise openings through curved surfaces or multiple layers.
- Generating Contours: Creating contour lines on terrain models by intersecting a plane with the terrain.
How to Use Intersect Faces
Using Intersect Faces typically involves a few straightforward steps:
- Position Geometry: Ensure the faces you want to intersect are overlapping or passing through each other as desired.
- Select Geometry:
- For specific objects: Select all the faces, groups, and/or components you wish to intersect.
- For the entire model: Select nothing (SketchUp will then operate on all visible geometry).
- Access the Command: Right-click on your selection (or anywhere in an empty area if nothing is selected).
- Choose "Intersect Faces": From the context menu, hover over "Intersect Faces."
- Select an Option: Choose one of the following intersection methods:
Intersect Faces Options
| Option | Description | Best Used When... |
|---|---|---|
| With Model | Intersects all selected geometry with everything else in the entire model's current context. This is the broadest option. | You need to intersect a few selected objects with a much larger or complex part of your model. |
| With Selection | Intersects the currently selected geometry only with other parts of the selected geometry. This is the most common and often safest choice. | You have two or more specific objects you want to intersect without affecting anything else. |
| With Context | Intersects selected geometry with other geometry that is in the same editing context. For instance, if you're editing a group, it will intersect selected items within that group with other items also within that group. | You are working inside a group or component and want to intersect parts of it without interacting with geometry outside that group/component. |
- Clean Up: After the command runs, SketchUp will have created new edges. You can then use the Eraser tool or Push/Pull tool to delete unwanted faces and edges, refining your model.
Practical Insights & Tips
- Work in Context: Always consider the editing context. If you want to intersect two groups, you generally need to either explode them first (not recommended if you want to keep them as groups) or open one group for editing, paste the other group's geometry into it (after copying), perform the intersection within that group, and then clean up.
- Make Groups/Components: Before intersecting, it's often beneficial to make the intersecting objects into separate groups or components. This prevents them from "sticking" together prematurely and gives you more control. Once you perform the intersection, you can decide whether to merge their geometry.
- Select Carefully: "Intersect Faces > With Selection" is usually the most controlled way to work. "With Model" can sometimes create unexpected edges on unrelated geometry if not used carefully.
- Cleanup is Key: The Intersect Faces command generates edges, but it doesn't automatically remove or create new faces for you. Be prepared to delete extra faces and edges to achieve the desired result.
By mastering Intersect Faces, you unlock a new level of precision and flexibility in your SketchUp modeling workflow, enabling you to tackle more intricate designs with confidence.
