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ScanMultipleEdges3D

Header:	AVL.h
Namespace:	avl
Module:	Vision3DStandard

Locates multiple changes of surface height along a given path.

Syntax

void avl::ScanMultipleEdges3D
(
	const avl::Surface& inSurface,
	const avl::ScanMap& inScanMap,
	const avl::EdgeScanParams3D& inEdgeScanParams,
	float inMinDistance,
	atl::Optional<float> inMaxDistance,
	atl::Optional<const avl::LocalBlindness&> inLocalBlindness,
	atl::Optional<int> inMaxProfileGapWidth,
	atl::Array<avl::SurfaceEdge1D>& outEdges,
	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
inMinDistance	float	0.0 -		Minimal distance between consecutive edges
inMaxDistance	Optional<float>	0.0 -	NIL	Maximal distance between consecutive edges
inLocalBlindness	Optional<const LocalBlindness&>		NIL	Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
inMaxProfileGapWidth	Optional<int>	0 -	NIL	Maximal number of consecutive not existing profile points
outEdges	Array<SurfaceEdge1D>&			Found surface edges
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 detects surface edges perpendicular to the path. Depending on the inEdgeScanParams.edgeTransition parameter, edges representing increase or decrease (or both) of surface height along the path will be taken into account.

When the number of edges to be found is known, one can use the ScanExactlyNEdges3D.

Note that in case of a scan path which is closed, the parameters controlling the distances between consecutive found objects do not control the distance between the first and the last of the found objects (counting from the beginning of the scan path).

The operation is very similar to ScanMultipleEdges 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.

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 too few edges are 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.
Adjust inMinDistance (in surface coordinates) to filter out false edges that appear in proximity to other edges.

Remarks

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