Section planes

A section plane cuts the model open, so you can look inside a building or a part. Geometry on one side of the plane disappears, the edges where the plane cuts faces show as heavy lines, and closed cuts are filled. Section planes are part of the model: they’re saved with it, and are selected, moved, rotated, copied, hidden and erased like other elements.

Place a section plane

Section Plane places planes.

1. Move the pointer over a face. The preview plane lies on the face, with arrows pointing at the side it keeps. In empty space the preview is level.
2. To place a plane across an axis instead, press Right for red, Left for green or Up for blue. Press the key again to free it. Hold Shift to keep the preview’s current orientation while you move the pointer to another point.
3. Click to place the plane.

The plane always faces away from the camera: it keeps what lies beyond it and cuts away the side you look from, so the cut faces you. Right after placing a plane, type to name it, then press Enter. New planes show the symbols 1, 2, 3 and so on; change the name and symbol in the Properties panel.

Which geometry a plane cuts

A new plane becomes the active cut of the context it’s placed in. Each context, the model or a group or component you’re editing, has at most one active cut, and making a plane active deactivates the context’s other plane. Inactive planes show gray and cut nothing.

The active cut of a context cuts everything in it, including the groups and components inside it. A plane placed inside a group cuts only that group’s contents, and every copy of a component cuts the same way. The model’s active cut and the active cuts of the groups around a piece of geometry all apply to it, up to four of them. When more than four nested contexts have active cuts, the innermost ones don’t cut.

Hiding a plane hides its symbol but keeps the cut. Put a plane on a hidden layer to stop it cutting.

Geometry a plane cuts away can’t be clicked or snapped to, but the cut itself offers On Section snaps along its lines.

Work with a plane

Right-click a section plane for:

• Active Cut makes the plane cut its context, or stops it cutting.
• Reverse turns the plane around, so it keeps the side it cut away.
• Align View turns the camera to look straight at the cut.

Double-clicking a plane also switches its cut on or off.

Moving or rotating a plane moves its cut. Erasing it shows its context whole again.

Section display

The View menu turns parts of the section display on and off without changing the model:

• Section Planes shows the planes’ symbols. Turn it off to see a clean cut.
• Section Cuts shows the cuts. Turn it off to see the whole model while keeping the planes active.
• Section Fill fills closed cuts in dark gray.

Scenes

A scene saves which planes are active and the section display settings. Showing the scene activates its planes, in one undo step with its layers, and turns the display settings back to what the scene saved. Scenes saved before section planes existed leave them as they are.

SketchUp files

Section planes in SketchUp files saved before SketchUp 2021 open with their names and symbols, inactive, since those files don’t say which plane cuts. Activate them from the right-click menu. Section planes in newer SketchUp files aren’t read yet.