/
Clip planes

Clip planes

Clip planes (also called cut planes) let you slice through your 3D model to reveal what's inside. Instead of hiding entire objects, a cut plane removes everything on one side of an infinite plane. This makes it easy to explore interiors, check alignments, and communicate design intent.

How it works

A cut plane is defined by two things:

  • Point — a position in the model that the plane passes through.

  • Normal vector — the direction the plane faces; this controls which side stays visible.

Geometry on the clipped side of the plane is hidden. The exposed surface can be tinted with a solid colour or given a soft fade size for clarity.

A clip plane is set by a point it passes through and the direction it faces. The clipPlaneIndex names it so you can move or disable it later — there are six slots: clipPlane and clipPlane2 through clipPlane6.

const options: ClipPlaneOptions = { clipPlaneIndex: 'clipPlane', enabled: true, normalVector: new Vector3(-1, 0, 0), // which way the plane faces — flip to (1,0,0) to keep the other side point: new Vector3(45, 0, 0), // a point on the plane, in model units color: Color3.Black(), // colours the cut surface so it stands out fadeSize: 0.1 // width of the coloured band on the cut, set to 0 to drop it }; api.viewer.setClipPlane(options);

See it in the playground: Clip plane.

Typical uses

  • Slice through floors to see room layouts.

  • Create cross-sections for structural inspection.

  • Hide outer walls to explore building interiors.

Controlling cut planes

  • Multiple planes can be added, moved, or disabled.

  • Individual objects (for example, floors or reference geometry) can be excluded so they are never cut. See Exclude objects from clipping.

  • Colours and fade settings can be adjusted to improve readability.

Tips and best practices

  • Disable backface culling. Cutting into a solid means you end up looking at the back of its faces, so turn off backface culling or the cut looks hollow. This gives a more realistic cross-section view.

  • Exclude key objects. Set ignoreClipPlanes = true on elements like floors or reference meshes if you want them always visible as context. See Exclude objects from clipping.

  • Use strong contrast. Pick a cut colour (for example black or bright red) that stands out against the model materials.

  • Slide the plane. Moving the plane point along an axis is a quick way to "scroll" through your model.

  • Flip the normal. Inverting the normal vector instantly switches which side is clipped — useful for quickly changing perspective.

  • Combine planes. Multiple cut planes can intersect, allowing box-like sections or very focused slices.

See also