How do I get rid of the green background?

I am playing around with a tree file I found online. It was actually pretty easy considering I just downloaded it, imported it, and threw the material together and it is almost complete already.

One thing left though, is that green background surrounding the tree. How do I remove it from the final material render?

Changed it to masked. Using the third material just makes everything black instead, including the tree.

I tried using alpha offset but I don’t think I know how to use it. I plugged the green into the alpha input and then tried a constant in the offset but it didn’t work. I tried a few other random things as well.

You may just change your material blend mode to Masked (look in material details, don’t forget to hit Apply) and feed your third texture directly into opacity mask, as it appears sufficiently bright. If it comes out with fringes or holes, you can tweak only the green channel with AlphaOffset. There are a number of alternative ways, however this one seems to be the fastest.

I put the diffuse.tga file into GIMP and it showed the correct alpha background but got exported into the editor without bringing the proper alpha information. I exported it as a png but that just smeared into the alpha.

How do I import the diffuse file with the proper information attached?

I dont know what options GIMP gives while saving an image as .TGA but make it 32 bit with alpha channel if you have that option.
TGA is more reliable for images with an alpha channel, btw.

The file is originally TGA so I was trying some other options. When I export the image to a .BMP it shows 32bit and A8/R8/G8/B8 both selected so I am assuming it does it for TGA and PNG automatically.

Since the original TGA file seems to have the correct alpha in GIMP, what could cause it to be green instead? Is there a way to import it properly? Texture/material settings inside the editor?

Are there TGA files that unreal editor can’t read? Maybe a TGA from an older version of the format or something? Gimp shows the proper background-removed image, but it gets into the editor either with a green or black background.

You don’t have any mask applied to this texture, nor is it a masked material. Also having texture the same colour as the background you want to remove afterwards is a terrible idea.