Compare a 3D scan with a CAD model
Last updated: 21 October 2026
DIMview can lay a reference model over a scanned part, align the two automatically and colour the part by how far it is from the reference. It is a fast visual check of a scan against its CAD model, in your browser and without uploading either file.
How to compare two models
- Open DIMview with the button below and open the model you want to colour, usually the scan as a mesh in STL, OBJ or PLY format.
- Press the Compare button in the 3D toolbar (the two arrows) and choose the reference model, usually the CAD model exported as STL, OBJ, PLY, GLB or glTF.
- DIMview aligns the reference to the model and colours the model. Green means the surface is within the tolerance. Beyond the tolerance the colour turns through yellow to red.
- Change the tolerance in the comparison panel. The colours update at once, without a new alignment.
What the panel shows
- the scale that was used to align the reference, for example 1.000x;
- the smallest, the largest and the average distance between the model and the reference;
- the percentage of the model's vertices that are within the tolerance;
- the tolerance in millimetres, which you can edit, and a legend of the colours.
The reference is drawn as a translucent blue ghost over the model, so you can see where it is thicker or thinner, shifted or missing.
How the alignment works, and what to check
The alignment is automatic. DIMview runs an iterative closest point routine on a sample of the reference points and solves position, rotation and a uniform scale. Then it measures, for every vertex of the model, the distance to the surface of the aligned reference.
Look at the scale in the panel. It should be close to 1.000. A value far from 1 means that the two files use different units, or that the models are not the same object. Because the scale is part of the fit, use this tool to find differences in shape, and measure key dimensions separately when the overall size matters.
When this is useful
- checking a scanned casting, bracket or tool against its CAD model before machining;
- seeing where a 3D printed part has warped or shrunk;
- finding out whether a reverse engineered CAD model really follows the scan it was built from;
- looking at wear on a part that has been in use.
Privacy
Both files are read and compared in your browser and are not uploaded. Scans and CAD models of customer parts stay on your device. Our visitor statistics count page views without cookies and never see the files (privacy policy).
What DIMview does not do
This is a visual check, not a certified inspection report. The scan has to be a triangle mesh, so a point cloud needs to be meshed in your scanner software first. The distances belong to the vertices of the coloured mesh, so a very coarse mesh gives few measuring points. For an inspection report with form and position tolerances, use metrology software.
Questions
Is the comparison free?
Yes. There are no ads, no account and no time limit.
Which files can I use as the reference?
STL, OBJ, PLY, GLB and glTF. If your CAD model is a STEP file, export an STL or OBJ from your CAD program for the comparison.
Can you scan the part for me?
Yes. MB PRECIZIUM scans parts, mechanisms, interiors and building exteriors across Lithuania and the Baltics, and the scan data supports measurement, quality control and reverse engineering. Contact us with a description of the part.