How to generate 2D orthographic sections directly from 3D IFC models

Skip the Revit round-trip — generate clean orthographic section drawings straight from an IFC file, scaled and ready to mark up.

The conventional path to producing a 2D section drawing from a 3D model goes through Revit: open the file, drop a section line, set the depth, configure visibility graphics, wait for the view to regenerate, export to PDF. For a coordinator who just needs a quick section to mark up during a clash review, that round-trip is heavyweight — especially when the model isn't even yours and you're working from an IFC export.

This post walks through how to generate clean orthographic section drawings directly from an IFC file without opening the source authoring tool. You pick the cut plane, the depth, and the sheet scale; the tool projects the model geometry, draws the lines at the correct weights, and hands you a scaled PDF ready for markup and takeoff.

Why go IFC-direct

The IFC file is the contractual deliverable on most modern A&E projects. It's also the discipline-neutral exchange format — the structural engineer sends IFC, the architect sends IFC, the mechanical contractor sends IFC, and the federated model that gets coordinated is whatever the team can stitch together from those exports.

Going IFC-direct for sections means:

• You don't need a Revit licence per coordinator — IFC is the input.
• The section reflects the federated model, not a discipline-specific slice of it.
• The section regenerates fast — IFC geometry is already in a flat indexable form, so projecting to a plane is a one-pass operation rather than a Revit view recalculation.
• You can section a model whose source authoring tool you don't have access to (a sub's GLB or a consultant's IFC from a different platform).

What "orthographic" means here

An orthographic section is a 2D projection of the 3D model onto a plane, with parallel projection (no perspective foreshortening). Elements behind the cut plane are clipped; elements in front of the cut plane are drawn at the line weights specified for "section" geometry; elements at the cut plane are filled (the "cut fill" — what a section drawing usually emphasises with hatching).

Three axes you can section along:

• Plan (XY plane at a Z elevation) — most common for floor plans and reflected ceiling plans.
• Building section (XZ or YZ vertical plane) — for the conventional "look at the building cross-section" view.
• Detail section (arbitrary plane) — a custom-oriented cut for one-off coordination needs.

LocusBIM's section tool exposes all three plus a free-rotation option for the arbitrary case.

Generating the section

Three inputs drive the geometry:

1. Cut plane — defined by a point and a normal vector. The UI exposes this as a planar widget you can drag in the 3D viewer.
2. View depth — how far behind the cut plane to draw. Shallow depth = clean architectural section; deep depth = shows mechanical runs behind the cut.
3. Sheet scale — 1:50, 1:100, 1:200 are typical for architectural sections. The output PDF is sized to fit the section at the chosen scale on a standard sheet size (A1, A3, ARCH D, etc.).

The tool projects all model geometry onto the cut plane, clips by depth, classifies each edge as "cut", "visible", or "hidden", and assigns line weights per industry convention (0.5 mm for cut edges, 0.25 mm for visible, 0.13 mm dashed for hidden).

Line weights matter — don't accept the default

The biggest visual difference between an IFC section that looks like a real drawing and one that looks like wireframe junk is line weight. Cut edges should be thick. Visible edges should be thin. Hidden lines should be dashed and thinner still. Without the hierarchy, the section is visually flat and reviewers can't tell what plane they're looking at.

A section drawing without a line-weight hierarchy is a wireframe export. A section drawing with the hierarchy is a real drawing — and you can hand it to a contractor without explaining what they're looking at.

The defaults in LocusBIM follow ISO 128-50 / ANSI Y14.2 conventions:

• Cut edges: 0.5 mm solid
• Visible edges (in front of cut): 0.25 mm solid
• Hidden edges (behind cut, within depth): 0.13 mm dashed
• Centrelines (for cylindrical elements): 0.13 mm chain-dashed

You can override per category — for example, push all mechanical-discipline edges to a heavier weight if the section is intended for MEP coordination.

Hatching the cut

Cut elements traditionally get a hatch fill that identifies the material. Concrete is hatched diagonally; steel is solid black; masonry has its own pattern; insulation is wavy.

LocusBIM reads the IFC material classification (IfcMaterial, IfcMaterialLayerSet) and applies hatch patterns from the bundled library. If the IFC lacks material data — which happens often, especially on models exported from non-Revit authoring tools — the fill defaults to a neutral grey so the cut is visible without making false claims about material.

Generating a takeoff from the section

Once you have the section as a calibrated PDF, the rest of LocusBIM's tooling kicks in: you can run cost impact directly on the section by marking it up, link markups back to the 3D elements they cut through (the same IFC GlobalId link covered in the 2D markups to 3D elements post), and export the combined PDF + markup set to BCF for round-trip exchange.

Because the section was generated at a known scale, area and length measurements on it produce real quantities — no separate calibration step required.

Where this falls down

A few honest caveats:

Section through a single-discipline IFC

If the IFC contains only the architectural discipline, the section won't show structure or MEP. That's not a tool limitation — it's a content limitation. Federate the IFC files first (you can load multiple IFCs into the same project; the tool stitches them on common world coordinates) so the section cuts through everything.

Curved or warped surfaces

Truly curved surfaces (toroidal HVAC ducts, swept-arch architecture) project correctly but display as polylines rather than splines. The output is geometrically correct; it just isn't as visually smooth as a Revit section would be. For coordination markup this is fine; for publication-quality drawing it isn't.

Annotation transfer

IFC carries geometry, not annotations. The section won't include the dimensions, text, and callouts that lived on the source Revit view. If you need those, the source-tool round-trip is still the right path. The IFC-direct path is for coordination sections, not contract drawings.

When to use this

This workflow shines in three scenarios:

1. Mid-coordination check — "what does it look like cut here?" gets answered in 30 seconds without opening Revit.
2. Consultant model review — you have the IFC, you don't have the source tool, you still need a markable section.
3. Federated cross-discipline section — every discipline's IFC stacked together, cut at the same plane, in one drawing.

It's not a replacement for Revit views for contract documentation — that's a different workflow with different constraints. But for the daily coordination back-and-forth, going IFC-direct removes hours per week of round-trip overhead.

Try it on your next federated review

The 30-day free trial unlocks the full IFC-direct section workflow including federated model loading, all three section axes, IFC-aware hatching, and calibrated PDF output. No credit card needed.