Solved by moskomule in post #2 
              
              
                Hi, 
if I understand correctly, the shape of label should be (batch_size)x64x128x128, because in a 2D case, the label should be (batch_size)x(height)x(width). 

Yes, the highest score stands for voxel class.
There’s no problem if the output includes negative values because they aren’t applied softma…