Measure Surface Flatness

Description

This Step is used to measure the flatness of a specified surface region.

Workflow

The process of configuring this Step is shown below.

Configure the input. Connect the ports manually or select the input(s) under Input in the parameter configuration panel.
Determine whether to use feature region.
Set other parameters.
Select the desired output(s) under Output. For an expandable output item, click ▶ and configure the Min and Max values of the acceptable range.
Run the Step and view output.

Parameter Description

Parameter

Description

Use Feature Region

Feature region defines the processing area to facilitate fitting the optimal plane. Once this parameter is selected, only data within or outside the feature region will be processed.

Feature Region Mode

Once “Use Feature Region” is selected, this parameter is used to set the mode of the feature region, i.e., to choose whether to use the data within the feature region to fit the plane and calculate the flatness, or to use the data outside the feature region to fit the plane and calculate the flatness.

Feature Region

For more information on how to set and adjust the feature region, see Feature Region.

Global Flatness Mode

This parameter determines which points on the surface are used to calculate global flatness.

All points:
- When no feature region is set, all data points on the surface will be used to fit the global plane and calculate flatness.
- When a feature region is set, the global plane is fitted and flatness is calculated according to the feature region.
Single average point: Use the average of data points inside or outside the feature region(s) to fit the global plane and calculate the flatness.

This option is only available when at least three feature regions are set, or else the Step will fail.

Data Filtering Mode

This parameter is used to select the data filtering method. Filter the data points according to the actual Z values before fitting the plane and calculating flatness.

None: No data filtering is performed.
Local percentile and Global percentile: “Local percentile” filters data according to the feature region; “Global percentile” filters global data. In both cases, percentiles must be set to define the range of Z values of data points. Data points outside the range will be filtered out.
- High Percentile: the percentile corresponding to the upper limit of the Z value of the data point.
- Low Percentile: the percentile corresponding to the lower limit of the Z value of the data point.
  
  When no feature region is set, both Local percentile and Global percentile indicate that the global data will be filtered.

Output Description

Select the output item(s) to add the output port(s) to the Step, and the corresponding data will be output after the Step is run. You can select the output according to the actual measurement requirements.

If you select an expandable output item, you must expand it by clicking ▶, and then set the Min and Max values to determine the acceptable range. If the output value falls within the acceptable range, the measurement item is judged as passing (OK), or else it is judged as failing (NG).

Output Item	Description
Global Min	The minimum distance from the data points involved in global plane fitting to the fitted global plane. The distance is positive for points above the plane and negative for points below the plane.
Global Max	The maximum distance from the data points involved in global plane fitting to the fitted global plane. The distance is positive for points above the plane and negative for points below the plane.
Global Flatness	The flatness of the globally fitted plane, which is the difference between Global Max and Global Min.
Global Min Point	The point representing Global Min.
Global Max Point	The point representing Global Max.
Global Average Point	The average point of all data points involved in global plane fitting.
Global Median Point	The median point of all data points involved in global plane fitting.
Global Plane	The fitted global plane.
Local Min	The minimum distance from the data points involved in local plane fitting to the fitted local plane. The distance is positive for points above the plane and negative for points below the plane. The number of output Local Min matches that of fitted local planes.
Local Max	The maximum distance from the data points involved in local plane fitting to the locally fitted plane. The distance is positive for points above the plane and negative for points below the plane. The number of output Local Max matches that of fitted local planes.
Local Flatness	The flatness of each fitted local plane, which is the difference between Local Max and Local Min.
Local Min Points	The points representing Local Min.
Local Max Points	The points representing Local Max.
Local Average Points	The average point of data points involved in the fitting of each local plane.
Local Median Points	The median point of data points involved in the fitting of each local plane.
Local Planes	Fitted local planes.

Output Item

Description

Global Min

The minimum distance from the data points involved in global plane fitting to the fitted global plane.
The distance is positive for points above the plane and negative for points below the plane.

Global Max

The maximum distance from the data points involved in global plane fitting to the fitted global plane.
The distance is positive for points above the plane and negative for points below the plane.

Global Flatness

The flatness of the globally fitted plane, which is the difference between Global Max and Global Min.

Global Min Point

The point representing Global Min.

Global Max Point

The point representing Global Max.

Global Average Point

The average point of all data points involved in global plane fitting.

Global Median Point

The median point of all data points involved in global plane fitting.

Global Plane

The fitted global plane.

Local Min

The minimum distance from the data points involved in local plane fitting to the fitted local plane.
The distance is positive for points above the plane and negative for points below the plane. The number of output Local Min matches that of fitted local planes.

Local Max

The maximum distance from the data points involved in local plane fitting to the locally fitted plane.
The distance is positive for points above the plane and negative for points below the plane. The number of output Local Max matches that of fitted local planes.

Local Flatness

The flatness of each fitted local plane, which is the difference between Local Max and Local Min.

Local Min Points

The points representing Local Min.

Local Max Points

The points representing Local Max.

Local Average Points

The average point of data points involved in the fitting of each local plane.

Local Median Points

The median point of data points involved in the fitting of each local plane.

Local Planes

Fitted local planes.

Troubleshooting

For common errors, see Error Code List.
If the error code is inconsistent with the error message, please contact Technical Support for help.

CV-W3103

Error: The value of “Low Percentile” should not be greater than that of “High Percentile,” or either of them is not within [0, 1].

Possible cause: The value of Low Percentile is greater than that of High Percentile, or either of them is not within [0, 1].

Solution: Reset the percentile to ensure that the percentile is within [0, 1] and that the value of Low Percentile is lower than that of High Percentile.

CV-W3104

Error: The selected data filtering mode is invalid.

Solution: Select a valid data filtering mode from the drop-down list.

CV-W3105

Error: Failed to fit the global plane.

Possible causes:

The number of points in the feature region is less than 3 and Global Flatness Mode is set to Single average point.
The number of points in the feature region is less than 3 and Global Flatness Mode is set to All points.

Solution:

When “Global Flatness Mode” is set to “Single average point”, adjust or add feature regions to ensure that the number of points in the feature region is equal to or greater than 3.
When “Global Flatness Mode” is set to “All points”, adjust or add feature regions to ensure that the number of points in the feature region is equal to or greater than 3.

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