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feature_viewer is an application available in ccny_rgbd which lets users test out different sparse feature detectors on top of RGBD data produced by rgbd_image_proc (or a compatible program). It allows users to change setting via dynamic_reconfigure and visualize features and their associated covariances in rviz.

feature_viewer is an auxiliary tool; it is not part of the visual odometry and mapping pipeline.

ROS API

Subscribed Topics

/rgbd/rgb (sensor_msgs/Image)

• Input RGB image

/rgbd/depth (sensor_msgs/Image)

• Input Depth image (registered in the RGB frame)

/rgbd/info (sensor_msgs/CameraInfo)

• CameraInfo, applies to both images.

Published Topics

feature/cloud (sensor_msgs/PointCloud2)

• Point cloud of the detected features

feature/covariances (visualization_msgs/Marker)

• Covariance matrices of the detected features. The 3x3 cov. matrix is visualized by the 3 principal components, each with a length of +/- 3 sigmas.

Parameters

General parameters

~queue_size (int, default: 5)

• input and output queue sizes

Feature parameters

~feature/detector_type (string, default: "GFT")

• Type of feature detector. Available types: "GFT", "SURF", "STAR", "ORB"

~feature/show_keypoints (bool, default: false)

• Whether to show the detected keypoint image in an OpenCV window.

~feature/publish_cloud (bool, default: false)

• Whether to publish the point cloud of 3D features

~feature/publish_covariances (bool, default: false)

• Whether to calculate and publish the covariance matrix markers

~feature/smooth (int, default: 0)

• Half-size of the window for the Gaussian smoothing kernel. 0 = no smoothing

~feature/max_range (double, default: 5.5)

• Maximum z-range, in meters, allowed for valid features

~feature/GFT/n_features (int, default: 400)

• (GFT detector only) Number of desired features

~feature/GFT/min_distance (int, default: 1)

• (GFT detector only) Minimum distance, in pixels, between detected features

~feature/ORB/n_features (int, default: 400)

• (ORB detector only) Number of desired features

~feature/ORB/threshold (double, default: 31.0)

• (ORB detector only) Detection threshold

~feature/STAR/min_distance (int, default: 2)

• (STAR detector only) Minimum distance, in pixels, between detected features

~feature/STAR/threshold (double, default: 32.0)

• (STAR detector only) Detection threshold

~feature/SURF/threshold (double, default: 400.0)

• (SURF detector only) Detection threshold

Usage

First, launch the device and image processing via ccny_openni_launch.

Note: You can use any launcher, as long as it outputs a registered depth and rgb image, and the corresponding CameraInfo (see API above).

roslaunch ccny_openni_launch openni.launch 

Next, launch the feature_viewer.launch:

roslaunch ccny_rgbd feature_viewer.launch 

This will start feature_viewer, rviz, and dynamic_reconfigure. A config file is passed to rviz for convenience.

The video below shows an overview of the functionality. We recommend viewing in HD and big window to see text clearly.

Here's a breakdown of what we demonstrate in the video:

• go to rgbd_image_proc, set publish_cluod to true

• go to feature_viewer_node, enable visualizations

• in feature_viewer_node, change detector type to "SURF"

• go to feature_viewer_node/feature/SURF, change threshold parameter