Unity + Photoshop : alpha cutoff

I'm trying to follow what this guy achieves with Gimp

while using photoshop

As far as I understood, you need to create another channel in photoshop and place in there the desired alpha cutoff gradient, I did it this way :



As you see in the pic the first visible layer is just an azure rectangle with the rest of the square just transparent, but in unity, placing this object on a plane gives a white background, even though the alpha cutoff works just fine. Am I missing something in Photoshop ? neither .tga or .png works this way

 

"Transparent background" doesn't exist in real-time rendering. In the end, in the file format (TGA/PNG), the RGB value of each pixel still exist. What appear transparent in Photoshop will be black or white depending on how Photoshop handles it.

If you want that "transparent" zone to be fully transparent, it needs to be fully black in the alpha channel on that desired spot.

 

Works. Thanks a lot