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# ScanSingleEdge3D

Header: AVL.h avl Vision3DStandard

Locates the strongest change of surface height along a given path.

### Syntax

C++
C#

void avl::ScanSingleEdge3D
(
const avl::Surface& inSurface,
const avl::ScanMap& inScanMap,
const avl::EdgeScanParams3D& inEdgeScanParams,
avl::Selection::Type inEdgeSelection,
atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
atl::Optional<int> inMaxProfileGapWidth,
atl::Conditional<avl::SurfaceEdge1D>& outEdge,
atl::Optional<avl::Profile&> outHeightProfile = atl::NIL,
atl::Optional<avl::Profile&> outResponseProfile = atl::NIL
)


### Parameters

Name Type Range Default Description
inSurface const Surface& Input surface
inScanMap const ScanMap& Data precomputed with CreateSurfaceScanMap
inEdgeScanParams const EdgeScanParams3D& Parameters controlling the surface edge extraction process
inEdgeSelection Selection::Type Selection::​Best Selection mode of the resulting edge
inLocalBlindness Optional<const LocalBlindness&> NIL Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
inMaxProfileGapWidth Optional<int> 0 - 1 Maximal number of consecutive not existing profile points
outEdge Conditional<SurfaceEdge1D>& Found surface edge
outHeightProfile Optional<Profile&> NIL Extracted surface height profile
outResponseProfile Optional<Profile&> NIL Profile of the edge (derivative) operator response

### Optional Outputs

The computation of following outputs can be switched off by passing value atl::NIL to these parameters: outHeightProfile, outResponseProfile.

### Description

The operation scans the surface using inScanMap previously generated from a scan path and locates the strongest edge perpendicular to the path. If the strongest edge is weaker than inEdgeScanParams.minMagnitude then the outputs are set to NIL.

The operation is very similar to ScanSingleEdge from 1D Edge Detection category, but there are some substantial differences. One of these is the possibility of absence of information, because some surface points may not exist at all. To detect such edges, where solely change of existence matters, Valid/Invalid options of inEdgeScanParams.EdgeTransition can be used. Outside the surface domain (i.e. rectangle defined by input surface width, height, offsets and scales) there are no valid or invalid points, so no edge can be found in the direct vicinity of the domain border.

Because in the Valid/Invalid mode all edges have equal strength, if inEdgeSelection is set to Best, it will be implicitly substituted with First selection option.

Please note that when the input surface has unequal scales along X and Y axes and the scan path is not parallel to any of the axes, the results may be slightly less accurate because of uneven sampling along axes.

### Hints

• Define inEdgeScanParams.EdgeTransition to detect a particular edge type, and only that type.
• If no edge is found, try decreasing inEdgeScanParams.MinMagnitude. Verify this with the values on the outResponseProfile output.
• If consecutive edges are closer than 6 pixels apart, change inEdgeScanParams.ProfileInterpolation to Quadratic3.

### Remarks

Read more about Local Coordinate Systems in Machine Vision Guide: Local Coordinate Systems.