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google-research / kubric

A data generation pipeline for creating semi-realistic synthetic multi-object videos with rich annotations such as instance segmentation masks, depth maps, and optical flow.
Apache License 2.0
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Negative values in the intrinsics matrix generated in MOVi? #273

Open ToughStoneX opened 1 year ago

ToughStoneX commented 1 year ago

I am trying to use the code provided in MOVi challenge to generate synthetic datasets by myself. But I am kind of confused about the format of intrinsic matrix of the generated data, because of the unexpected negative values. For example, the intrinsic matrix of the generated data is:

[[  1.09375, 0,           -0.5],
 [  0,       -1.09375,    -0.5],
 [  0,       0,           -1]]

Usually, the format of intrinsic matrix is defined as follows:

[[fx, 0,  cx],
 [0,  fy, cy],
 [0,  0,  1]]

It seems that the negative values in the third column ([-0.5, -0.5, -1]^T) conflict with the well-used one ([cx, cy, 1]^T) as far as I know. Could you please explain the setting of these negative values in the intrinsic matrix?

zhangzjjjjjj commented 2 weeks ago

@ToughStoneX Hi, I encountered the same issue when projecting the world coordinate system into the camera coordinate system. Have you been able to find a solution yet?