I'm having some alpha problems when loading my B3D level.

As you can see the transparent part is just black.
Is this my fault?, do I have to enable alpha on the model or something?
I've tried to save the PNG in Photoshop and GIMP, both have the same result.

As you can see the transparent part is just black.
Is this my fault?, do I have to enable alpha on the model or something?
I've tried to save the PNG in Photoshop and GIMP, both have the same result.