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BREP Viewer

Open Open CASCADE .brep shapes in the browser and inspect exact solids without installing FreeCAD.

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About This Tool

BREP is the native boundary-representation file of the Open CASCADE kernel. FreeCAD's Part workbench and other Open CASCADE applications write .brep when a shape should stay exact topology instead of becoming a mesh or a STEP exchange file. This viewer tessellates those faces in your browser: closed solids draw as a shaded mesh, and curves that were not sewn into a shell draw as wires. Drag to rotate, scroll to zoom toward the cursor, and use the right or middle button to pan. Parsing runs in local WebAssembly.

Tips

  • 1Reads Open CASCADE text and binary .brep
  • 2Closed solids shade as a mesh; loose curves stay wires
  • 3Large shapes draw coarse first, then a finer mesh replaces them

About Configuration Options

Preview settings

Auto-rotate

DefaultOff

Slowly rotate the model around the vertical axis after loading for a full view. Can be toggled anytime in the left panel.

On

Auto-rotate after loading

OffRecommended

Stay still, rotate manually only (default)

Animation

Clips

Number of animation clips stored in the file.

Bones

Number of skeleton bones used for rigging and skinning.

Format Information

Input format

Extension:
brep
Full Name:
BREP (Boundary Representation)
Type:
CAD Model
Format:
BREP
Tools:
FreeCAD、SALOME
Open With:
3D Model Viewer、BREP Viewer
Description:
BREP is the native shape file of the Open CASCADE kernel. A .brep file stores exact boundary-representation topology: vertices, edges, wires, faces, shells, and solids, carried by analytic curves and NURBS surfaces rather than a triangle mesh. FreeCAD's Part workbench and other Open CASCADE applications write it when a shape should be saved without converting it into a neutral exchange file. Unlike STEP, this file is a kernel dump. It has no product structure, assembly metadata, materials, or textures. Closed solids are tessellated in the browser into a shaded mesh, and curves that were not sewn into a shell stay as wires. Use it to inspect an Open CASCADE shape you already have. Use STEP when the model has to move into SolidWorks, Fusion, or another CAD system.

Notes:

  • Exact Open CASCADE topology, not a stored triangle mesh
  • No materials, textures, or assembly product structure

Supported Features:

  • Open CASCADE native shape file
  • Exact faces, edges, shells, and solids
  • Text and binary BREP
  • Written by FreeCAD Part and other Open CASCADE applications

How to Use

1

Load the BREP file

Drop a .brep file onto the page. Parsing runs in the browser.

2

Let the finer mesh catch up

A large shape draws a coarse mesh first. Wait for the finer tessellation to replace it before judging small edges.

3

Separate solids from wires

Shaded bodies are closed shapes. Wires are curves that were not sewn into a shell.

4

Orbit the shape

Drag to rotate, scroll to zoom toward the cursor, and pan with the right or middle mouse button.

Frequently Asked Questions

View all FAQs
Q

What is a .brep file?

A

A .brep file is the shape container written by the Open CASCADE kernel. It stores boundary-representation topology, from vertices and edges through faces, shells, and solids, using exact curves and surfaces. FreeCAD's Part workbench writes this when you export a shape as BREP.

Q

How is a BREP file different from STEP?

A

STEP is a neutral exchange standard meant to move models between CAD systems, and it can carry product and assembly structure. BREP is the kernel's own shape dump. Open CASCADE applications read it directly. SolidWorks and Fusion do not treat .brep as an import format. Keep BREP inside that toolchain, and export STEP when the file has to travel.

Q

Why does the shape look faceted?

A

The file keeps exact surfaces. The viewer tessellates them into triangles so a browser can draw them. On a large shape a coarse mesh appears first, then a finer pass replaces it. Those triangles are only a display approximation. They are not stored in the .brep file.

Q

Why are some parts only wires?

A

Closed solids become a shaded mesh. Curves and wires that were not sewn into a closed shell stay as line geometry. An open shell, or a wire that never became a face, will not look like a solid body.

Q

Which programs write .brep files?

A

FreeCAD Part export, SALOME, and applications built on Open CASCADE write .brep. A BREP solid mentioned inside SolidWorks or Fusion is usually a solid inside a STEP file, not this extension. Check that the file name actually ends in .brep.

Q

The file will not open. What should I check?

A

This viewer reads Open CASCADE text BREP, whose header contains CASCADE Topology, and the kernel's binary BREP. A truncated download, a STEP or mesh file renamed to .brep, or a shape from another kernel will not parse. Re-export the shape from FreeCAD as BREP and open that file.

Q

Can I turn this shape into an STL on this page?

A

No. This page only inspects the shape. It does not measure dimensions and it does not edit the topology. Open the same file in the model converter to export a mesh such as STL or GLB. That mesh is the tessellation used for display, not the exact surfaces stored in the file.