Unit of flow values - Githubissues

MarianoJT88 / Joint-VO-SF

Fast Odometry and Scene Flow from RGB-D Cameras based on Geometric Clustering

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Unit of flow values #4

Open jthsieh opened 6 years ago

jthsieh commented 6 years ago

I ran VO-SF-ImagePair and successfully got the ClusterFlow.xml file. However, I am having trouble interpreting the values. The values are all ~ 10^-2 or smaller. In contrast, the raw values of the example depth images are ~ 10^4.

Shouldn't the x, y flow values be in pixels, and z flow values be in some distance metric (e.g. mm)?

MarianoJT88 commented 6 years ago

All the scene flow components are expressed in meters, I have just added a comment about that in the README.md

jthsieh commented 6 years ago

Thank you! Sorry I am fairly new to depth images and 3D optical flow, so a few more questions:

Why are the x, y flow values also in meters (instead of pixels)? How are you able to calculate the real distance between two pixels?
I briefly read the code, and when you read the depth images, you scale it by a factor of 1.0/5000 with this line of code, depth.convertTo(depth_float, CV_32FC1, 1.0 / 5000.0); I guess the question is what's the format of the depth image?

MarianoJT88 commented 6 years ago

You can calculate the real displacement because you know the geometry of the scene (from depth images and the pinhole camera model).

The expected format of the depth images is described in the README.MD. It is the same as in the famous TUM RGB-D Dataset (https://vision.in.tum.de/data/datasets/rgbd-dataset)