Manufacturing & engineering
Deviation analysis
Definition
Deviation analysis measures and displays the distance between reference geometry and another curve, surface, or mesh. In scan-to-CAD work it is used to show where a rebuilt model sits above or below the measured scan and whether selected regions fall within declared bounds.
Also known as: deviation map, mesh deviation analysis, surface-to-mesh deviation
Updated
What can be compared#
SOLIDWORKS Design 2026 supports surface-to-mesh, curve-to-mesh, and mesh-to-mesh comparisons. A scan-to-CAD workflow can therefore check a fitted surface against the measured mesh, inspect a reconstructed section curve, or confirm that mesh cleanup has not moved the working data beyond a chosen limit.
The software samples distances and displays them as colours or spines. Upper and lower bounds control the displayed range, and a report can retain numerical results. The comparison still depends on the alignment between the two datasets and on which regions were selected.
Interpreting the colour map#
A deviation map needs a stated sign convention, bounds, units, coordinate system, and model revision. A mostly green plot means the sampled distances fall inside the configured central band. It does not prove that the band matches a product tolerance or that the underlying scan is accurate.
Review critical interfaces separately from cosmetic or freeform regions. A bearing seat, sealing face, or mounting pattern may need a tighter fit and an independent dimensional check. A styled outer surface may use wider bounds while still requiring surface continuity review.
What deviation cannot prove#
Deviation analysis compares two representations. It does not identify which one is nominal, recover design intent, validate scanner calibration, or account automatically for measurement uncertainty, wear, coatings, or deformation in the physical sample.
Use the result with the original point cloud, alignment record, fitted-feature assumptions, and applicable tolerance. The scan-to-CAD guide shows how that evidence supports an editable model without pretending one used part is a perfect master.
Sources
Related terms
Point cloud
A point cloud is a set of measured coordinates that sample the surface or surroundings of a physical object in three dimensions. The points may also carry colour or intensity, but they do not by themselves define connected faces, exact curves, material volume, or CAD feature history.
Mesh
A mesh represents a shape as a surface of small flat polygons, almost always triangles, joined at shared edges and vertices. Meshes work well for rendering, games, and 3D printing, but they have no true faces, edges, or exact curves, so they are hard to dimension or edit as engineering geometry.
Surface modeling
Surface modeling creates and edits zero-thickness faces that define the outer boundary of a shape without enclosing material or volume. It is used for complex curvature, product styling, face repair, and hybrid workflows where surfaces are later stitched, knit, or thickened into a solid.
Tolerance
A tolerance is the allowed variation from a nominal dimension, such as 10.00 ± 0.05 mm. Tolerances drive fit, cost, and inspection, and they have to be specified deliberately because a CAD model on its own stores only nominal sizes.