rtabmap_ros/rtabmap_util/doc/point_cloud_xyzrgb.md

point_cloud_xyzrgb

Projects an RGB-D frame, a stereo pair or a disparity image into a colored point cloud.

The colored counterpart of point_cloud_xyz: same filtering, same parameters, but every point carries the color of the pixel it came from. It accepts four different input sets, so it can sit at the end of an RGB-D, stereo or disparity pipeline without anything in between.

Contents

• Usage
• Subscribed Topics
• Published Topics
• Parameters
• Stereo matching
• Notes

Usage

ros2 run rtabmap_util point_cloud_xyzrgb --ros-args \
  -r rgb/image:=/camera/color/image_raw \
  -r depth/image:=/camera/aligned_depth_to_color/image_raw \
  -r rgb/camera_info:=/camera/color/camera_info \
  -p decimation:=4 -p voxel_size:=0.05

ComposableNode(
    package='rtabmap_util',
    plugin='rtabmap_util::PointCloudXYZRGB',
    name='point_cloud_xyzrgb',
    parameters=[{'decimation': 4, 'voxel_size': 0.05}],
    remappings=[('rgb/image', '/camera/color/image_raw'),
                ('depth/image', '/camera/aligned_depth_to_color/image_raw'),
                ('rgb/camera_info', '/camera/color/camera_info')])

Subscribed Topics

Four independent input sets; connect exactly one.

RGB-D

Topic	Type	Description
rgb/image	sensor_msgs/msg/Image	mono8, mono16, bgr8, rgb8, bgra8, rgba8 or bayer_grbg8.
depth/image	sensor_msgs/msg/Image	32FC1, 16UC1 or mono16, registered to the color camera.
rgb/camera_info	sensor_msgs/msg/CameraInfo

Stereo

Topic	Type	Description
left/image	sensor_msgs/msg/Image	Rectified.
right/image	sensor_msgs/msg/Image	Rectified.
left/camera_info	sensor_msgs/msg/CameraInfo
right/camera_info	sensor_msgs/msg/CameraInfo	Its P(0,3) carries the baseline.

Dense matching is done on the fly with OpenCV's block matcher; see Stereo matching.

Disparity

Topic	Type	Description
left/image	sensor_msgs/msg/Image	Supplies the color.
disparity	stereo_msgs/msg/DisparityImage	32FC1 or 16SC1.
left/camera_info	sensor_msgs/msg/CameraInfo

Bundled

Topic	Type	Description
rgbd_image	rtabmap_msgs/msg/RGBDImage	A whole frame in one message, RGB-D or stereo. No synchronization needed, so this is the most reliable input.

Published Topics

Topic	Type	Description
cloud	sensor_msgs/msg/PointCloud2	XYZRGB, or XYZRGBNormal when normals are enabled.

Nothing is computed unless cloud has a subscriber.

Parameters

Identical to point_cloud_xyz, with image_transport added and the Stereo* family below.

Synchronization

Parameter	Type	Default	Description
approx_sync	bool	true	Match the inputs by nearest stamp. Set false when they share exact stamps.
approx_sync_max_interval	double	0.0	Reject sets spanning more than this many seconds. 0 disables.
topic_queue_size	int	1	Queue depth of each input subscription.
sync_queue_size	int	10	Queue depth of the synchronizer.
qos	int	0	Reliability of the image and disparity subscriptions.
qos_camera_info	int	value of qos	Reliability of the camera info subscriptions.
image_transport	string	"raw"	image_transport plugin for the color, left and right images.
depth_transport	string	"raw"	image_transport plugin for depth/image.

Projection and filtering, applied in this order

Parameter	Type	Default	Description
decimation	int	1	Keep one pixel in decimation, in each direction.
roi_ratios	string	""	Crop before projecting, "left right top bottom". Ignored for stereo input, which warns if you set it.
min_depth	double	0.0	Discard points nearer than this, in meters. 0 disables.
max_depth	double	0.0	Discard points further than this, in meters. 0 disables.
voxel_size	double	0.0	Downsample to one point per voxel, in meters. 0 disables.
noise_filter_radius	double	0.0	Radius outlier removal, in meters. 0 disables.
noise_filter_min_neighbors	int	5	Neighbors needed within noise_filter_radius.
normal_k	int	0	Estimate normals from this many neighbors. 0 disables.
normal_radius	double	0.0	Estimate normals within this radius. 0 disables.
filter_nans	bool	false	Drop invalid points instead of leaving them NaN, giving an unorganized cloud. See point_cloud_xyz.

Stereo matching

The stereo and rgbd_image-with-stereo inputs run OpenCV's block matcher, configured through RTAB-Map's StereoBM/* parameters, which are exposed as ROS parameters of this node:

-p StereoBM/NumDisparities:=64 -p StereoBM/BlockSize:=15

The full list is in RTAB-Map's parameter reference. The two that matter most are StereoBM/NumDisparities (must exceed the largest disparity you expect, and must not exceed the image width) and StereoBM/BlockSize.

If you already have a disparity image, feed the disparity input instead — it skips the matching entirely.

Notes

For RGB-D input the depth must be registered to the color camera: the node pairs pixel (u,v) of the color image with pixel (u,v) of the depth image and uses one calibration for both. Unregistered depth gives a cloud whose colors are offset from its geometry. Most drivers offer an aligned depth stream for this reason.

An rgbd_image carrying only color and no depth is valid and yields an empty cloud rather than an error.