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ScanSingleEdge3D

Module:	Vision3DStandard

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

Name	Type	Range	Description
inSurface	Surface		Input surface
inScanPath	Path		Path along which the scan is performed
inScanPathAlignment	CoordinateSystem2D *		Adjusts the scan path to the position of the inspected object
inSamplingStep	Real *	0.0 -	Distance between consecutive sampling points on the scan path; if Nil, the bigger of surface X and Y scales is chosen
inScanWidth	Integer	1 -	Width of the scan field in pixels
inSurfaceInterpolation	InterpolationMethod		Interpolation method used for extraction of surface points
inEdgeScanParams	EdgeScanParams3D		Parameters controlling the surface edge extraction process
inEdgeSelection	Selection		If many edge points are possible, defines which one is selected
inLocalBlindness	LocalBlindness *		Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
inMaxProfileGapWidth	Integer *	0 -	Maximal number of consecutive not existing profile points
outEdge	SurfaceEdge1D ?		Found surface edge
outAlignedScanPath	Path		Path along which the scan is performed; in the image coordinate system
outHeightProfile	Profile		Extracted surface height profile
outResponseProfile	Profile		Profile of the edge (derivative) operator response
diagSamplingPoints	Path Array		Array of paths each one containing the sampling points that contributed to a single value of the extracted profile; in the image coordinate system
diagSamplingStep	Real		Used distance between consecutive sampling points on the scan path

Description

The operation scans the surface along inScanPath 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 optional parameter inScanPathAlignment defines a transform to be performed on the inScanPath so that the actual scan path (outAlignedScanPath) is adjusted to the position of the object.

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

Connect an input surface to the inSurface input.
Create inScanPath which is more or less perpendicular to the edge you want to detect. It should be long enough to anticipate all possible edge locations.
Define inEdgeScanParams.EdgeTransition to detect a particular edge type, and only that type.
Use a local coordinate system connected to inScanPathAlignment to automatically adjust the measurement to variable object position (optional).
If the noise level is high, try increasing inScanWidth and/or inEdgeScanParams.SmoothingStdDev.
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.

Complexity Level

This filter is available on Basic Complexity Level.

Filter Group

This filter is member of ScanEdges3D filter group.