inquiry meaning about " label - 1" , thanks!!

[emilyemliyM]

Dear author,
I got confused about func "SemKITTI2train_single" about "label-1".
what does the function want to do?

def SemKITTI2train(label):
if isinstance(label, list):
return [SemKITTI2train_single(a) for a in label]
else:
return SemKITTI2train_single(label)

def SemKITTI2train_single(label):
return label - 1 # uint8 trick

[edwardzhou130]

SemanticKITTI uses label 0 as the 'unlabeled' class.

PolarSeg/semantic-kitti.yaml

Lines 144 to 164 in 3531f15

	learning_map_inv: # inverse of previous map
	0: 0 # "unlabeled", and others ignored
	1: 10 # "car"
	2: 11 # "bicycle"
	3: 15 # "motorcycle"
	4: 18 # "truck"
	5: 20 # "other-vehicle"
	6: 30 # "person"
	7: 31 # "bicyclist"
	8: 32 # "motorcyclist"
	9: 40 # "road"
	10: 44 # "parking"
	11: 48 # "sidewalk"
	12: 49 # "other-ground"
	13: 50 # "building"
	14: 51 # "fence"
	15: 70 # "vegetation"
	16: 71 # "trunk"
	17: 72 # "terrain"
	18: 80 # "pole"
	19: 81 # "traffic-sign"

Our model won't predict this class during training. So each gt label needs to be shifted down by 1 when calculating the loss.