How to Use 3D Comparison in BricsCAD Mechanical

Quick answer: 3DCOMPARE compares two 3D models, 3D solids and surfaces stored in two DWG files, including models imported into BricsCAD from other file formats. It can process large models, reports differences in the Mechanical Browser panel, and supports multiple visualization modes, confirming the difference-node behaviour covered exactly on this hub’s Mechanical Browser page.

How Comparison Works

A 3D model is a DWG file containing one or more 3D solids or surfaces. When comparing two, BricsCAD first tries to align them automatically in 3D space for maximum similarity, then compares every face of those solids and surfaces geometrically, within a given tolerance. Models count as equal if every face in the first file has an equal face in the second, and vice versa. A difference is a full face, or part of a face, with no equal counterpart found in the other file; two or more differences merge into a single group if they’re geometrically adjacent to each other.

A difference node creates in the Mechanical Browser panel for each group of adjacent differences; expand it to see the individual differences it’s made of. Selecting a difference in the panel highlights the corresponding feature directly in the drawing.

Accessing 3D Comparison

Use the tools on the 3D Compare toolbar to run the comparison procedure.

Visualizing the Comparison

3DCOMPARE creates a new DWG document named Compare_<File_1>_<File_2>.dwg, with the two compared models attached as external references. A special Comparison layout generates automatically with two viewports, one per drawing, illustrating the differences with color.

Display is controlled by 3DCOMPAREMODE: with any value other than 0, the corresponding model becomes semi-transparent while differences display in distinct colors, each difference painted its own individual shade. Zoom in on a specific difference via the Mechanical Browser’s context menu.

Displaying Differences: Two-Viewport Method

1. Click the Left Viewport and/or Right Viewport tool button.
2. Double-click inside one of the viewports.
3. Use mouse and keyboard shortcuts to manipulate the display (zoom in or out, rotate, and so on); the other viewport syncs automatically, letting you compare the same part on both models in detail.

Displaying Differences: Single-Viewport Method

Click the Single Viewport tool button instead; the differences display directly in model space.

Frequently Asked Questions

What counts as a “difference” between two compared 3D models? A full face, or part of a face, that has no equal counterpart found on the other model, within the set tolerance.

Does moving the view in one viewport affect the other during comparison? Yes, with the two-viewport method, the other viewport syncs automatically so you can compare the same part on both models in detail.

Can I compare models that were imported into BricsCAD from a different file format? Yes, 3DCOMPARE works on any 3D model, including ones imported from other formats.

How do I quickly navigate to a specific detected difference? Select it in the Mechanical Browser panel and use its context menu to zoom in.