[Pixel layer (alpha) used as mask]

aaah, ok. 

Thank you Anon!

Telemax, the mask below command  was what I was doing, It works except... there is no transparency, the mask seems to be applied just like in your exemple but I can't see the layer beneath through the mask.

 

[Pixel layer (alpha) used as mask]

Hello

Former photoshop user, I'm just starting with Affinity Photo.

I do Archiviz images from multi passes layers rendered from a 3d  program, mixing / comping them onto a picture of the real location. One think I'm used to do is rendering B/W images of the objects also named Alphas. As those are pixel layers, I need to use them as masks to hide parts of a layer and reveal what's beneath. I tried with the mask to below fonction but there is no transparency in my pixel layer even thought the mask seems to be applied correctly, I can't see the other layers below.

I'm sure It must be something simple...

 

Thank you!