Question about the channels of patch tensors

[jinyummiao]

Hi, thanks for your remarkable work!
How, i am trying to understand the code of DPVO, but some problems confuse me.
In the transform function of projective_ops.py, we can get X0 based on patches and intrinsics, and X0 is constructed as [X Y 1 d]. However, after transforming using Gij, i saw that transformed results X1 donot have any channel equals to 1, which seems confusing, and its construction is like [X Y Z H] in the following code. What's the meaning of H?
Thanks at advances.