How do I make a section cut in a BIM model online?

Open the model in the browser viewer, activate Section planes in the toolbar, and click any surface of the model. A cutting plane appears where you clicked, with an arrow gizmo you drag to sweep the cut through the building. Everything runs locally in the browser — the IFC is parsed on your device, so there is no upload and no account.

Can I cut the model at an angle?

The plane's orientation follows the surface you click, so you get an angled cut by clicking an angled face: a sloped roof or a ramp yields a plane parallel to that slope. Clicking a facade gives a vertical section, clicking a floor slab gives a horizontal plan cut. There is no free-rotation handle on the plane itself — pick the cut direction by picking the right surface.

Why can't I select elements while section mode is active?

Deliberately: while the tool is active, every click on the model places a new plane, so element selection is suspended to keep the two gestures from fighting each other. Press Esc to leave section mode — the cuts stay in place — and clicks go back to selecting elements, which you can then isolate, hide or measure in the sectioned view.

Can I use several section planes at the same time?

Yes — keep clicking surfaces and each click adds another plane, all cutting simultaneously. A vertical plane plus a horizontal one opens a corner of the building like a dollhouse; two parallel verticals carve out a slice around a single axis. The red trash button removes every plane at once when you want the whole model back.

Are section cuts saved with the model or exported to it?

No — the cuts are a view state, not model data. The IFC file is never modified, and closing the model discards the planes. To keep a finding, save a PNG snapshot of the sectioned view from the toolbar and attach it to your report or issue; to keep the underlying evidence, note the elements involved via the properties panel.

Section analysis: how to cut a BIM model open in the browser

Updated August 3, 2026 · BIMViewer team

A BIM model cut open by a section plane in the browser viewer

From the outside, a building model shows you almost nothing that matters. The questions that fill coordination meetings — does the riser line up between storeys, what's really inside that wall build-up, is there room above the ceiling for the duct and the cable tray — are all interior questions. Section analysis is how you ask them: slicing the model along a plane so the hidden arrangement becomes the visible one. This article covers how the section tool in our browser viewer works and the checks coordinators run with it every week.

Why coordinators live in section cuts

A federated model is precisely the place where the interesting collisions hide: services from one file threading through structure from another, plant rooms packed by three different subcontractors, shafts that each discipline modelled from its own reference. Orbiting the outside tells you the massing is right; only a cut tells you whether the inside works. That's why section planes sit in the everyday toolkit next to measurement and isolation, not in some advanced menu — for anyone reviewing BIM models for coordination, cutting is as routine as zooming.

How section planes work in this viewer

Activate Section planes in the toolbar and the viewer switches modes, showing a hint: click the model to add a section plane, drag the arrow to move it. Click any surface and a cutting plane appears right there, carrying an arrow gizmo — drag the arrow and the plane sweeps through the building, peeling geometry away in real time as it travels.

The key design decision: the plane's orientation follows the surface you click. Click a facade and you get a vertical section through the building; click a floor slab and you get a horizontal plan cut; click a sloped roof and the cut follows the slope. Instead of wrestling axis controls, you choose the cut by choosing the surface — the gesture matches how you already think about the building.

Keep clicking to add more planes; they all cut at once, so a vertical and a horizontal plane together open up a corner like a dollhouse view. The red trash button clears every plane, and Esc leaves the mode. One deliberate trade-off to know about: while section mode is active, clicking selects nothing — clicks place planes. Press Esc first, then select, isolate or measure within the cut you've made.

IFC model sliced by a section plane in the browser viewer, with the draggable arrow gizmo visible — A live cut through one of the demo models — drag the arrow to sweep the plane.

Three cuts coordinators make every week

Checking a shaft storey by storey

Click a floor slab to get a horizontal cut, then drag the arrow upward so the plane climbs the building level by level while you orbit above it — left-drag orbits, right-drag pans, the wheel zooms. A shaft or riser that drifts out of alignment between storeys is obvious in seconds this way, because you're watching the same opening appear and move in plan as the cut rises.

Inspecting a facade build-up

Click the facade itself: the resulting vertical plane starts at the outer face, and dragging it inward a few centimetres at a time exposes the wall's layers in order — cladding, cavity, insulation, structure, finish. Zoom in close and step the cut through the assembly; it's the closest thing to peeling the wall open, and a quick way to confirm that what was modelled matches what was specified.

Reviewing MEP above a ceiling

Place a horizontal cut just under the slab of the storey above, so the plenum becomes the top layer of what's visible. Then leave section mode with Esc and thin the scene: select and hide the ceiling grid or whatever else is noise, or isolate the duct runs alone. The combination — cut to expose the zone, isolate to silence the clutter — is how a crowded ceiling void turns into a picture you can actually reason about.

Cuts plus measurements, federation and snapshots

A section cut rarely ends an argument by itself; its job is to expose the thing you then check. Cut first, then measure: once the plane reveals the gap between the duct and the beam, the measure tool tells you whether that gap is a clearance or a clash-in-waiting. And a cut through a federated scene is the sharpest interface check available — load the architecture, add the structural model into the same scene, and slice through both at once to see exactly where one discipline meets the other. (When a milestone needs that combined model as a single file rather than a view, the IFC merge tool produces one federated IFC.)

When the cut shows something worth acting on, save a PNG snapshot from the toolbar. A sectioned, isolated view with a measurement in frame communicates an issue better than any written description — and the colleague who receives it can open the same file in the same free viewer and stand in front of the same cut within a minute.

What a section cut is not

Honesty about scope: the cuts here are visual analysis, not an issue-management pipeline. There is no BCF export attached to a plane, and no automatic clash detection running behind the cut — the viewer exposes the geometry and you bring the judgement, with the measure tool as your witness. For many everyday checks that's exactly enough, and it costs nothing and uploads nothing; for formal clash workflows, the cut is where you verify and communicate what the clash report claims. One habit makes every cut more trustworthy: audit each discipline file before it enters the scene, because a section through a broken model answers questions nobody asked.