Pointclouds from outdoor stereo cameras

source: http://www.pointclouds.org

We tested an algorithm, developed by Alex Trevor in the previous HRI code sprint. This algorithm segments points using their normal distribution, this makes it very sensitive to noise.

Basically, this algorithm computes a disparity for a stereo pair using its own dense matching method, implemented by Federico Tombari. But I additionally tested it using disparity maps precomputed by HRI. Here are the typical results (left – disparity is computed with Federico Tombari’s method, right – precomputed by HRI):

castro_results_hrcs1

You can see that Federico Tombari’s method is friendlier to the normal-based algorithm. But it is not good enough for describing a scene, there are a lot of false positives.

Some noise is presented at the HRI’s disparity maps, even a lot of pixels have no valid disparity, sometimes there are no segments that are similar to road and there are a lot frames in which road was not found.

This algorithm has thresholds for disparity and doesn’t mark as “road” any point which doesn’t satisfy these thresholds. I didn’t take it to account because it would make these results not completely correct. Therefore, 50% recall would be a very good result.

The goal is find all pixels, that belong to the road. Total results are on the image below (precision is a ratio of right detected road’s points to all detected pixels, recall is a percent of detected road’s points):

castro_results_hrcs1_total

 

HRCS Stereo Segmentation

The Honda Research Code Sprint for ground segmentation from stereo has been completed. PCL now includes tools for generating disparity images and point clouds from stereo data courtesy of Federico Tombari, as well as tools for segmenting a ground surface from such point clouds from myself. Attached is a report detailing the additions to PCL and the results, as well as a video overview of the project. There is a demo available in trunk apps, as pcl_stereo_ground_segmentation.


 

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