Filter Surface Points by Normals
Description
This Step is used to exclude unwanted surface points by their normals so that a better surface can be obtained.
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Before filtering |
After filtering |
Workflow
The process of configuring this Step is shown below.
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Configure the input. Connect the Step ports in the graphical programming workspace or select the input under Input in the parameter configuration panel.
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Determine whether to use a feature region. For more information, see Use Feature Region.
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Set the angle parameters.
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Set other parameters.
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Select the output item Depth Map (selected by default).
Parameter Description
- Use Feature Region
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Feature region defines the surface region to be filtered. When this option is selected, this Step will only process data within or outside the feature region.
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Feature Region Mode
This parameter is used to set the mode of the feature region, that is, to select whether to filter the surface data within the feature region or to filter the data outside the feature region.
Options: Include data in Region, Exclude data in Region
Instruction: To filter surface data within the feature region, select Include data in Region; otherwise, select Exclude data in Region.
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Feature Region
For more information on how to set the feature region, see Set the Feature Region.
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Keep Unfiltered Data
Once this parameter is selected, the unfiltered data will be retained in the output. Unselected by default.
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- Angle-Based Filtering
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The relevant parameters are explained as follows:
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Min Polar Angle: The minimum acceptable angle of the normals with respect to the Z-axis.
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Max Polar Angle: The maximum acceptable angle of the normals with respect to the Z-axis.
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Min Z Angle: The minimum acceptable angle of the XOY projection of normals clockwise around the Z-axis and relative to the positive X direction.
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Max Z Angle: The maximum acceptable angle of the XOY projection of normals clockwise around the Z-axis and relative to the positive X direction.
As shown in the figure above, OA is the normal, and OB is the XOY projection of OA; ∠a is the polar angle of OA while ∠b is the Z angle of OA.
The parameters Min/Max Polar Angle and Min/Max Z Angle specify the angle filtering range for normals. Data points with normal’s polar angle or Z angle outside the specified range will be excluded.
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- Remove Noise
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As noise can be introduced by normal calculation, select the noise removal level according to the tolerance to noise.
Options: None, Small, Medium, Large
- Smooth Size
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The size of the filter window.
Apply a mean filter to the surface data before calculating the normals to avoid abrupt normal changes due to noise. The default value is 1.
Normal Vector Calculation
- Normal Search Radius
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Points within a circle with the set search radius will be used to calculate normals. The unit is millimeters (mm). The default value is 1.000.
- Half Kernel Size
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Points within a square with a side length twice the set half kernel size will be used to calculate the normals. The unit is pixels. The default value is 1.
Output Description
The output of this Step is a processed depth map that can be used as input to other Steps.
Troubleshooting
Invalid Parameter
| No. | Error | Possible Causes | Solution |
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1 |
Inappropriate smooth size |
The set smooth size is less than 1. |
Reset Smooth Size and ensure that the value exceeds 1. |
2 |
Inappropriate polar angle |
The set polar angle is not within the range of 0–90°. |
Reset Min / Max Polar Angle to ensure that the polar angle is within the range of 0–90°. |
3 |
Inappropriate Z angle |
The set Z angle is not within the range of 0–360°. |
Reset Min / Max Z Angle to ensure that the Z angle is within the range of 0–360°. |
4 |
Inappropriate normal search radius |
The set normal search radius is not greater than 0. |
Reset Normal Search Radius and ensure that the value exceeds 0. |
5 |
Inappropriate half kernel size |
The set half kernel size is not greater than 0. |
Reset Half Kernel Size and ensure that the value exceeds 0. |