3D Matching and Classification (Multiple Models)

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Function

This Step can match the objects in the scene by using multiple point cloud models and output the poses and class labels of the objects.

Usage Scenario

This Step is usually used for the matching and classification of a single object in the scene. If there are multiple objects in the scene, point cloud clustering or deep learning can be utilized to segment objects first and then each object can be matched and classified by using this Step.

Input and Output

After inputting the point clouds of objects, this Step will output the object poses with the same amounts as point clouds.

The input and output of this Step are shown below with the example of inputting a point cloud of a single object.

Input

Input port	Data type	Description
Point Cloud (with normals)	PointCloud/XYZNormal[]	The list of point clouds input to this port will be matched with the point cloud models.

Input port

Data type

Description

Point Cloud (with normals)

PointCloud/XYZNormal[]

The list of point clouds input to this port will be matched with the point cloud models.

Output

Output port	Data type	Description
Object Pose	Pose[]	Matched target object poses.
Object Point Clouds (with normals)	PointCloud/XYZNormal[]	Point clouds of the objects.
Object Class Labels	String[]	Class labels of the objects.
Pose Confidence Values	Number[]	List of confidence values of the corresponding object poses.

Output port

Data type

Description

Object Pose

Pose[]

Matched target object poses.

Object Point Clouds (with normals)

PointCloud/XYZNormal[]

Point clouds of the objects.

Object Class Labels

String[]

Class labels of the objects.

Pose Confidence Values

Number[]

List of confidence values of the corresponding object poses.

Parameter Description

Parameter	Description
Parameter Tuning Level	Parameter description: This parameter is used to select the Parameter Tuning Level for the Step. Value list: Basic and Advanced. Default value: Basic

Parameter

Description

Parameter Tuning Level

Parameter description: This parameter is used to select the Parameter Tuning Level for the Step.
Value list: Basic and Advanced.
Default value: Basic

Basic Parameter Tuning Level

Model Settings

Parameter

Description

Select Target Object

Parameter description: This parameter is used to select the target object that is configured in the target object editor.

Tuning instruction: After making a point cloud model with the target object editor, click the button to the right of the parameter to expand the drop-down list to select or switch the point cloud model file.

The point cloud model type should be the same. You cannot select Surface point cloud model and Edge point cloud model at the same time.
The sizes of the point cloud models should not differ too much. It is recommended that the difference between the largest point cloud model and the smallest one should not exceed 1.5 times. Otherwise, the matching speed will be affected. If there is a large disparity in the sizes of the point cloud models, it is recommended to classify the input scene point cloud first by using the Classify Point Clouds by Dimensions Step.

Parameter

Description

Matching Mode

Parameter description: This parameter is used to select between Edge Matching and Surface Matching modes.

Value list: Surface matching, Edge matching.

Default value: Surface matching.

Tuning recommendation: When the surface of the object has obvious recognizable features (such as crankshafts, rotors, and steel rods), it is recommended to use surface matching. You should create a point cloud model that represents the surface features of the object. When the object is relatively flat and shows clear and regular edge features under the camera (such as panels, track pads, connecting rods, and brake discs), it is recommended to use edge matching. You should create a point cloud model that represents the edge features of the object.

If you select Edge matching, you should input the point clouds which are extracted the edges.

Coarse Matching Settings

Parameter

Description

Operation Mode

Parameter description: This parameter is used to select the operation mode for coarse matching.

Value list: High speed, Standard, High accuracy, Extra-high accuracy, and Custom.

Instruction: Under all kinds of operation modes, the matching accuracy and speed are different due to different number of points in the point cloud models. The following table provides a detailed description.

Expected Point Count of Model

Parameter description: This parameter is used to set the expected number of points in the point cloud model.

Default value: 200

Instruction: Set this parameter when Operation Mode is Custom.

Tuning recommendation: Please set the parameter according to the actual requirement.

When the matching or classification results are not satisfactory, it is recommended to prioritize the adjustment of this parameter to increase the “Expected Point Count of Model.”

Operation Mode	Number of Points in the Point Cloud Models	Matching Characteristics
High speed	200	High speed, low accuracy
Standard	300	Relatively stable
High accuracy	400	High accuracy, low speed
Extra-high accuracy	500	Highest accuracy
Custom	Custom	Determined by customized number of points

Operation Mode

Number of Points in the Point Cloud Models

Matching Characteristics

High speed

200

High speed, low accuracy

Standard

300

Relatively stable

High accuracy

400

High accuracy, low speed

Extra-high accuracy

500

Highest accuracy

Custom

Determined by customized number of points

Fine Matching Settings

Parameter	Description
Operation Mode	Parameter description: This parameter is used to select the operation mode for fine matching. Value list: High speed, Standard, High accuracy, and Extra-High accuracy. Instruction: Please refer to the operation modes of the “Coarse Matching Settings.”

Parameter

Description

Operation Mode

Parameter description: This parameter is used to select the operation mode for fine matching.
Value list: High speed, Standard, High accuracy, and Extra-High accuracy.
Instruction: Please refer to the operation modes of the “Coarse Matching Settings.”

Validation Settings

Parameter	Description
Confidence Threshold	Parameter description: If the confidence of the matching result is above the threshold, the matching result is valid. The higher the confidence value is, the more accurate the matching result is. Default value: 0.300

Parameter

Description

Confidence Threshold

Parameter description: If the confidence of the matching result is above the threshold, the matching result is valid. The higher the confidence value is, the more accurate the matching result is.
Default value: 0.300

Advanced Parameter Tuning Level

Model Settings

Parameter

Description

Select Target Object

Parameter description: This parameter is used to select the target object that is configured in the target object editor.

The point cloud model type should be the same. You cannot select Surface point cloud model and Edge point cloud model at the same time.
The sizes of the point cloud models should not differ too much. It is recommended that the difference between the largest point cloud model and the smallest one should not exceed 1.5 times. Otherwise, the matching speed will be affected. If there is a large disparity in the sizes of the point cloud models, it is recommended to classify the input scene point cloud first by using the Classify Point Clouds by Dimensions Step.

Coarse Matching Settings

Parameter	Description
Operation Mode	Parameter description: This parameter is used to select the operation mode for coarse matching. Value list: High speed, Standard, High accuracy, Extra-high accuracy, and Custom. Instruction: Under all kinds of operation modes, the matching accuracy and speed are different due to different number of points in the point cloud models. The following table provides a detailed description.
Expected Point Count of Model	Parameter description: This parameter is used to set the expected number of points in the point cloud model. Default value: 200 Instruction: Set this parameter when Operation Mode is Custom. Tuning recommendation: Please set the parameter according to the actual requirement. [TIP] ==== When the matching or classification results are not satisfactory, it is recommended to prioritize the adjustment of this parameter to increase the “Expected Point Count of Model”. ===
Upper Limit of Point Pair Count per Feature	Parameter description: This parameter is used to specify the maximum number of point pairs contained in each feature during the model analysis. The smaller this value is, the faster the processing speed, but the lower the accuracy of the matching results. Default value: 50

Parameter

Description

Operation Mode

Parameter description: This parameter is used to select the operation mode for coarse matching.

Value list: High speed, Standard, High accuracy, Extra-high accuracy, and Custom.

Expected Point Count of Model

Parameter description: This parameter is used to set the expected number of points in the point cloud model.
Default value: 200
Instruction: Set this parameter when Operation Mode is Custom.
Tuning recommendation: Please set the parameter according to the actual requirement.
[TIP] ==== When the matching or classification results are not satisfactory, it is recommended to prioritize the adjustment of this parameter to increase the “Expected Point Count of Model”. ===

Upper Limit of Point Pair Count per Feature

Parameter description: This parameter is used to specify the maximum number of point pairs contained in each feature during the model analysis. The smaller this value is, the faster the processing speed, but the lower the accuracy of the matching results.
Default value: 50

Operation Mode	Number of Points in the Point Cloud Models	Matching Characteristics
High speed	200	High speed, low accuracy
Standard	300	Relatively stable
High accuracy	400	High accuracy, low speed
Extra-high accuracy	500	Highest accuracy
Custom	Custom	Determined by customized number of points

Operation Mode

Number of Points in the Point Cloud Models

Matching Characteristics

High speed

200

High speed, low accuracy

Standard

300

Relatively stable

High accuracy

400

High accuracy, low speed

Extra-high accuracy

500

Highest accuracy

Custom

Determined by customized number of points

Voting Settings

Parameter	Description
Distance Quantification	Parameter description: The parameter for the quantification of the distance between points (Distance between Two Points=Distance Quantification*Sampling Interval). The larger the value is, the less accurate the matching results. Default value: 1.00
Angle Quantification	Parameter description: The parameter for the quantification of the angle between the normals of the points in the point pair (Angle between Two Vectors = 360°/Angle Quantification). The larger this value is, the more accurate the matching results, but it also requires higher point cloud quality. Default value: 60
Vote Ratio Lower Threshold	Parameter description: In the matching process, each object pose will earn a score. When the pose score is higher than the “product of Highest Score in the Vote and Vote Ratio Lower Threshold,” the corresponding pose will be involved in the pose verification. The lower this value is, the more likely an exact match will be found, but the execution time will also be longer. Default value: 0.80
Referring Point Sampling Step	Parameter description: This parameter is used to adjust the step size to downsample the scene point cloud and obtain referring points that form point pairs with the referred points. When the value is larger, the interval sampling points are fewer, and the execution speed is faster, but the matching accuracy is reduced. Default value: 5
Referred Point Sampling Step	Parameter description: This parameter is used to adjust the step size to downsample the scene point cloud and obtain referred points that form point pairs with the referring points. When the value is larger, the interval sampling points are fewer, and the execution speed is faster, but the matching accuracy is reduced. Default value: 1

Parameter

Description

Distance Quantification

Parameter description: The parameter for the quantification of the distance between points (Distance between Two Points=Distance Quantification*Sampling Interval). The larger the value is, the less accurate the matching results.
Default value: 1.00

Angle Quantification

Parameter description: The parameter for the quantification of the angle between the normals of the points in the point pair (Angle between Two Vectors = 360°/Angle Quantification). The larger this value is, the more accurate the matching results, but it also requires higher point cloud quality.
Default value: 60

Vote Ratio Lower Threshold

Parameter description: In the matching process, each object pose will earn a score. When the pose score is higher than the “product of Highest Score in the Vote and Vote Ratio Lower Threshold,” the corresponding pose will be involved in the pose verification. The lower this value is, the more likely an exact match will be found, but the execution time will also be longer.
Default value: 0.80

Referring Point Sampling Step

Parameter description: This parameter is used to adjust the step size to downsample the scene point cloud and obtain referring points that form point pairs with the referred points. When the value is larger, the interval sampling points are fewer, and the execution speed is faster, but the matching accuracy is reduced.
Default value: 5

Referred Point Sampling Step

Parameter description: This parameter is used to adjust the step size to downsample the scene point cloud and obtain referred points that form point pairs with the referring points. When the value is larger, the interval sampling points are fewer, and the execution speed is faster, but the matching accuracy is reduced.
Default value: 1

Pose Verification Settings

Parameter	Description
Use Distance NMS	Parameter description: After this parameter is selected, candidate poses whose distances to the selected poses are less than 0.1 times the diameter of the object will be filtered out. Default value: selected.
Voxel Length Generation Strategy	Parameter description: This parameter is used to select the method to generate the voxel length. Default value: Auto. Tuning recommendation: “Auto” is recommended to be used for new users.
Voxel Length	Parameter description: This parameter is used to set the length (mm) of the voxel. The larger the value, the less accurate the matching results. Default value: 3.000 mm
Voxel Length Lower Limit	Parameter description: This parameter is used to set the minimum voxel length (mm). Default value: 1.000 mm
Voxel Length Upper Limit	Parameter description: This parameter is used to set the maximum voxel length (mm). Default value: 15.000 mm

Parameter

Description

Use Distance NMS

Parameter description: After this parameter is selected, candidate poses whose distances to the selected poses are less than 0.1 times the diameter of the object will be filtered out.
Default value: selected.

Voxel Length Generation Strategy

Parameter description: This parameter is used to select the method to generate the voxel length.
Default value: Auto.
Tuning recommendation: “Auto” is recommended to be used for new users.

Voxel Length

Parameter description: This parameter is used to set the length (mm) of the voxel. The larger the value, the less accurate the matching results.
Default value: 3.000 mm

Voxel Length Lower Limit

Parameter description: This parameter is used to set the minimum voxel length (mm).
Default value: 1.000 mm

Voxel Length Upper Limit

Parameter description: This parameter is used to set the maximum voxel length (mm).
Default value: 15.000 mm

Pose Filtering Settings

This parameter group needs to be adjusted in the edge matching mode.

Parameter	Description
Filter Poses by Model Rotation Angle	Parameter description: In the edge matching mode, the point cloud model may need to be rotated by a certain angle to match with the scene point cloud, and the poses will be filtered by the point cloud model’s rotation angle. When the model’s rotation angle exceeds the “Angle Difference Upper Threshold,” the pose will be filtered out. Default value: selected.
Angle Difference Upper Threshold	Parameter description: Please refer to the parameter “Filter Poses by Model Rotation Angle” for details.

Parameter

Description

Filter Poses by Model Rotation Angle

Parameter description: In the edge matching mode, the point cloud model may need to be rotated by a certain angle to match with the scene point cloud, and the poses will be filtered by the point cloud model’s rotation angle. When the model’s rotation angle exceeds the “Angle Difference Upper Threshold,” the pose will be filtered out.
Default value: selected.

Angle Difference Upper Threshold

Parameter description: Please refer to the parameter “Filter Poses by Model Rotation Angle” for details.

Fine Matching Settings

Parameter	Description
Deviation Correction Capacity	Parameter description: This parameter is used to set the intensity of the deviation correction to the matching result from 3D Coarse Matching. The greater the deviation correction capacity is, the more likely the coarsely matched poses can be corrected to the accurately matched poses. Please note that an excessive deviation correction capability may lead to a loss of matching accuracy. Value list: Small, Medium, and Large. Default value: Small.
Operation Mode	Parameter description: You can refer to the Basic Parameter Tuning Level.

Parameter

Description

Deviation Correction Capacity

Parameter description: This parameter is used to set the intensity of the deviation correction to the matching result from 3D Coarse Matching. The greater the deviation correction capacity is, the more likely the coarsely matched poses can be corrected to the accurately matched poses. Please note that an excessive deviation correction capability may lead to a loss of matching accuracy.
Value list: Small, Medium, and Large.
Default value: Small.

Operation Mode

Parameter description: You can refer to the Basic Parameter Tuning Level.

Symmetry settings

Parameter	Description
Symmetry Axis	Parameter description: This parameter is used to select the axis of rotational symmetry to rotate the initial pose of the object. Value list: ROTATE_BY_X, ROTATE_BY_Y, and ROTATE_BY_Z Default value: ROTATE_BY_Z
Symmetry Angle Step (0–360)	Parameter description: This parameter is used to set the step to change the initial orientation from “Min Rotation Angle” to “Max Rotation Angle.” The unit is degree (°). Default value: 360.0° Tuning instructions: The value of “Symmetry Angle Step” parameter should be greater than 0.
Min Rotation Angle	Parameter description: This parameter specifies the minimum rotation angle for the pose rotation according to the “Symmetry Angle Step.” The unit is degree (°). Default value: -180.0°
Max Rotation Angle	Parameter description: This parameter specifies the maximum rotation angle for the pose rotation according to the “Symmetry Angle Step.” The unit is degree (°). Default value: 180.0°

Parameter

Description

Symmetry Axis

Parameter description: This parameter is used to select the axis of rotational symmetry to rotate the initial pose of the object.
Value list: ROTATE_BY_X, ROTATE_BY_Y, and ROTATE_BY_Z
Default value: ROTATE_BY_Z

Symmetry Angle Step (0–360)

Parameter description: This parameter is used to set the step to change the initial orientation from “Min Rotation Angle” to “Max Rotation Angle.” The unit is degree (°).
Default value: 360.0°
Tuning instructions: The value of “Symmetry Angle Step” parameter should be greater than 0.

Min Rotation Angle

Parameter description: This parameter specifies the minimum rotation angle for the pose rotation according to the “Symmetry Angle Step.” The unit is degree (°).
Default value: -180.0°

Max Rotation Angle

Parameter description: This parameter specifies the maximum rotation angle for the pose rotation according to the “Symmetry Angle Step.” The unit is degree (°).
Default value: 180.0°

Validation Settings

This parameter group needs to be adjusted in the surface matching mode.

Parameter	Description
Only Consider Visible Surface of Model	Parameter description: Once this parameter is selected, only the visible part of the surface point cloud model will be involved in the matching, which facilitates the calculation and produces a more reasonable matching confidence. Default value: Unselected. Tuning recommendation: It is recommended to select this parameter for object models that have parts not visible to the camera under a viewing angle, such as the complete model of a cylindrical object. For object models that are completely visible from the same viewing angle, such as the surface matching model of the upper side of a brake disc, this parameter can be ignored.

Parameter

Description

Only Consider Visible Surface of Model

Parameter description: Once this parameter is selected, only the visible part of the surface point cloud model will be involved in the matching, which facilitates the calculation and produces a more reasonable matching confidence.
Default value: Unselected.
Tuning recommendation: It is recommended to select this parameter for object models that have parts not visible to the camera under a viewing angle, such as the complete model of a cylindrical object. For object models that are completely visible from the same viewing angle, such as the surface matching model of the upper side of a brake disc, this parameter can be ignored.

Result Visualization

Parameter	Description
Visualization Options	Parameter description: After “Debug Output” is enabled, the selected option will be generated and displayed. Value list: Coarse matching result, Fine matching result, Downsampled model for coarse matching, Downsampled model for fine matching, Downsampled scene point cloud for coarse matching, Downsampled scene point cloud for fine matching. Default value: Fine matching result.
Only Visualize Current Matching Result	Parameter description: Once this parameter is selected, only the matching result corresponding to the current model will be visualized. Default value: Unselected. Instruction: Select the model for visualization if this parameter is unselected.
Select Model for Visualization	Parameter description: This parameter is used to select the point cloud model that you want to visualize. Tuning recommendation: Set this parameter after unselect Only Visualize Current Matching Result.

Parameter

Description

Visualization Options

Parameter description: After “Debug Output” is enabled, the selected option will be generated and displayed.
Value list: Coarse matching result, Fine matching result, Downsampled model for coarse matching, Downsampled model for fine matching, Downsampled scene point cloud for coarse matching, Downsampled scene point cloud for fine matching.
Default value: Fine matching result.

Only Visualize Current Matching Result

Parameter description: Once this parameter is selected, only the matching result corresponding to the current model will be visualized.
Default value: Unselected.
Instruction: Select the model for visualization if this parameter is unselected.

Select Model for Visualization

Parameter description: This parameter is used to select the point cloud model that you want to visualize.
Tuning recommendation: Set this parameter after unselect Only Visualize Current Matching Result.

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