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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 the MOVI datasets #331

Open andrewsonga opened 2 months ago

andrewsonga commented 2 months ago

Hello,

I've been playing around with the Movi dataset, and I found something odd about the intrinsics matrix:

K = [[1.09375, 0.0, -0.5],
        [0.0, -1.09375, -0.5],
        [0.0, 0.0, -1.0]]

AFAIK the intrinsics matrix should have the form of 

K = [[fx, 0.0, -cx],
        [0.0, fy, -cy],
        [0.0, 0.0, 1.0]]

where fx, fy, cx, cy > 0. What does it mean when the intrinsics matrix has negative values i.e. entries K_11 = -1.09375 and K_22 = -1.0?

Thank you in advance!

zhangzjjjjjj commented 1 month ago

@andrewsonga Hi, I encountered the same issue when projecting the world coordinate system into the camera coordinate system. Have you found a solution yet?