ProAut Pointcloud Filter

Introduction

This package was designed to remove simple geometric shapes from pointclouds. E.g. A cube or a sphere. Several of these filters can be applied to a pointcloud in one shot. For more details on the types of filters and their parameters see Filters.

This package includes a full node and a ros interface for one’s own node. For more details about the node, like topic names and parameters, see Node.

The package can handle three different input types of pointclouds:

• sensor_msgs/PointCloud2 (this is also the output type)
• sensor_msgs/PointCloud
• sensor_msgs/LaserScan

Additionaly the input data can be throttled to reduce the cpu load.

Node

rosrun pcdfilter_pa pcdfilter_pa_node
roslaunch pcdfilter_pa pcdfilter_pa.launch

Input and Output Topics

All topics can be remapped using parameters (see below).

Services

Parameters

Filter

Parameter Name | Type | Description ———————–|——————-|————————————- “~/filters” | vector of strings | All pointcloud filters as an array of strings.

general settings

Parameter Name | Type | Description ———————–|——————-|————————————- “~/skip_count” | integer | Input throttling. Number of skipped messages after each processed message. “~/skip_time” | double | Input throttling. Time intervall in seconds. After each processed message, this intervall starts and all input messages will be skipped. “~/tf_lookup_time” | double | Maximum time in seconds for waiting for a specific TF transform. “~/buffer_pointcloud” | bool | Flag for buffering the last received pointcloud. This can be used to test different filters without resending the some pointcloud. “~/debugging” | bool | Flag for enabling extented output. “~/enabled” | bool | Flag for setting start up behaviour. Indicates if node is filtering at startup, or not.

laser

Parameter Name | Type | Description ———————–|——————-|————————————- “~/laser_nan_replacement_value” | double | If a nan-value is represented within the laser scan, it might indicate “no obstacle within range”. Therefore this parameters will replace those values with a fixed number.

topics and services

Parameter Name | Type | Description ———————–|——————-|————————————- “~/topic_in_cloud” | string | Name of input topic for new pointclouds. “~/topic_in_cloud_old” | string | Name of input topic for old pointclouds. “~/topic_in_laser” | string | Name of input topic for laser scans. “~/topic_out_cloud” | string | Name of output topic for filtered pointcloud.

See also this config file. It contains all parameters and their default value.

Filter

Definition

This is the definition of every single filter as a string.

[<inversion>]<type> <separator> <dimensions> <tf> [<tf_offset>] [<tf2> [<tf2_offset>]] [# <comment>]

inversion (optional)

Inversion | Description ———-|————————————————————– “” (none) | normal behaviour; points within the volume will be filtered out; all points outside will be kept “!” | reversed behaviour; points within the volume will be kept; all points outside will be filtered out

type

Type | Description | Nr Parameters | Nr TF ids ———–|———————————–|—————|———- “cube” | specified by its sidelength | 1 parameter | 1 TF “sphere” | specified by its radius | 1 parameter | 1 TF “block” | cuboid specified by its three sidelengths in x,y and z direction | 3 parameters | 1 TF “cylinder” | specified by its radius and its height | 2 parameters | 1 TF “link” | cylinder centered around the two given tfs; specified by its radius and its overshoot | 2 parameters | 2 TF “cone” | cone headed at fist tf and pointing to second tf; specified by its height and its ratio (radius/height) | 2 parameters | 2 TF

separator

Seperator | Description ———-|————————————————————– “:” | current filter is required; if some tf is missing the whole filtering is aborted and no output pointcloud is generated “?” | current filter may be skipped; if some tf is missing then the current filter is not applied; but in any case the whole filtering and output process is continued

To control how long the filter should wait for the necessary tf there exists a parameter “~/tf_lookup_time” - see also Node.

dimensions

Number of dimensions depends on the type of the current filter(see above). At least one dimension is always needed, e.g. for a cube. Three dimensions must be set for a cuboid.
Each dimension is a single number seperated by spaces.

tf

ROS frame id for the filtered objects.

tf_offset (optional)

This allows for an additional offset relative to the given frame id. Order of parameters: x y z qx qy qz qw

Missing parameters will be set to “0”. If qw is not set then it will be set to sqrt(1 - qx^2 - qy^2 - qz^2)

tf2 and tf2_offset (optional)

Only valid for type “link” and “cone”.
For description see above (tf and tf_offset).

comment

Every character following ‘#’ is ignored. This can be used to give a short comment.

Examples

cube: 3 base_footprint

Filters every point within the following cube - the cube is removed from the pointcloud.
The sidelength is 3 [meters].
The center is aligned with TF frame “base_footprint”.
Corners will be at [+/-1.5 , +/- 1.5, +/- 1.5].

!sphere: 2.3 map

Only points within sphere will stay.
The center of sphere is aligned with TF frame “map”.
The radius is 2.3 [meters] and the diameter is 4.6 [meters].

block: 1 2 3 base_link 0.5 1 1.5

Removes every point within the cuboid.
One corner of the cuboid is at center of TF frame “base_link”.
This is due to the additional offset of [0.5, 1 1.5].
Two opposite corners are at [0, 0, 0] and [1, 2, 3].

link: 0.2 0 arm_link1 arm_link2

Removes every point within the cylinder, which is attached to both TF frames.
The center of the top and bottom surface is exactly at origin of one frame (zero overshoot).
The radius is 0.2 [meters].
The height depends only the relative position of the two frames.
Also the orientation of the cylinder is not fixed to any frame.

!cone: 10 1 laser pan_tilt_tilt_link

Removes every point outside the cone.
The top of cone will be at the origin of the TF frame “laser” and the centerline will go straight through the origin of the TF frame “pan_tilt_tilt_link”.
The height is 10 [meters].
The angle at the top is 90 degrees (ratio of radius to height is 1:1).

Links and packages

Source code at github

https://github.com/TUC-ProAut/ros_pcdfilter

Related packages

https://github.com/TUC-ProAut/ros_parameter

ROS packages

ros-kinetic-pcdfilter-pa

ROS Build-Status and Documentation

ROS-Distribution	Build-Status	Documentation
Indigo	EOL April 2019	docs.ros.org/indigo
Jade	EOL May 2017	docs.ros.org/jade
Kinetic		docs.ros.org/kinetic
Lunar	EOL May 2019	docs.ros.org/lunar
Melodic	upcoming	docs.ros.org/melodic