Query about center offset

facebookresearch / 3detr

Code & Models for 3DETR - an End-to-end transformer model for 3D object detection

Apache License 2.0

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Closed gopi-erabati closed 3 years ago

gopi-erabati commented 3 years ago

Thank you for your work, it seems interesting!

Is 0.5 subtracted from center head to make offset in range [-0.5, 0.5] ?
As center offset is added to query points to get unnormalized center, is this based on assumption that center of object lies within +/- 0.5 m from the query point ? Can you please shed some light on this!

imisra commented 3 years ago

Thanks!

Yes, since the center output is used after a sigmoid [0, 1], it cannot directly predict negative offsets. So we convert it to [-0.5, 0.5].
You are right, this assumes that the object is within +/- 0.5m. We had tried variants where we used output = scale * (center_output_after_sigmoid - 0.5) where scale > 1 and found that it did not improve performance. So, we stuck with the simpler scale = 1 setting.