compute_hausdorff_distance returns units

[LReion]

compute_hausdorff_distance calculates the unit returned by the Euclidean distance. If the spacing is not set, is the default spacing=(1.,1.,1.)? Is the unit of the final result in mm?

[KumoLiu]

Hi @LReion, thanks for your interest.
Yes, you are right, if spacing is None, spacing of unity is used for all images in the batch. And the actual distance measurements can vary based on your data.

MONAI/monai/metrics/hausdorff_distance.py

Lines 165 to 171 in faf6f74

	spacing: spacing of pixel (or voxel). This parameter is relevant only if ``distance_metric`` is set to ``"euclidean"``.
	If a single number, isotropic spacing with that value is used for all images in the batch. If a sequence of numbers,
	the length of the sequence must be equal to the image dimensions. This spacing will be used for all images in the batch.
	If a sequence of sequences, the length of the outer sequence must be equal to the batch size.
	If inner sequence has length 1, isotropic spacing with that value is used for all images in the batch,
	else the inner sequence length must be equal to the image dimensions. If ``None``, spacing of unity is used
	for all images in batch. Defaults to ``None``.

Hope it helps, thanks!