Using -1 to represent background causes error

[LambdaGuard]

td3d/mmdet3d/datasets/pipelines/transforms_3d.py

Lines 524 to 535 in 33d8073

	num_pts_per_inst_src = pts_instance_mask_one_hot.sum(axis=0)
	pts_instance_mask = torch.cat((torch.tensor(input_dict['pts_instance_mask'][new_idxs]), inst_idxs))
	idxs_sum = (pts_instance_mask == -1).sum()
	pts_instance_mask[pts_instance_mask == -1] = torch.max(pts_instance_mask) + 1
	pts_instance_mask_one_hot = torch.nn.functional.one_hot(pts_instance_mask)
	if idxs_sum > 0:
	pts_instance_mask_one_hot = pts_instance_mask_one_hot[:, :-1]
	pts_instance_mask_one_hot = pts_instance_mask_one_hot[:-len(inst_idxs), :]
	num_pts_per_inst = pts_instance_mask_one_hot.sum(axis=0)
	good_insts = num_pts_per_inst / num_pts_per_inst_src > self.remaining_points_thr

Here, if one uses -1 to represent background, the calculation of good_insts will raises error for the shapes of these two tensors does not fit. This is because pts_instance_mask_one_hot is cut in line 531 and 'num_pts_per_inst' will have an extra element.

The solution is to move line 524 to 532, after 'if'.