I’m exploring the new render elements functions of v1.5 
Its looking really exciting with the ability to render using vRayMtlSelect. I’m just not sure of the best way to use this facility in my workflow. I tried rendering this out as a TGA with alpha, but the tga didn’t have any alpha data. Do I need to manually key the VRayMtlSelect channel in post using a VRayMtlMaterialID as the matt?
I ve tried vraymtlselect too. It’s great! Have u tried to composite it using the ADD blending mode (or linear dodge in photoshop, i think). This way u dont need any alpha at all…
But do all the channels composite correctly if using ADD ?
I tried compositing something as per the thread on compositing vray g-buffers, but certain things didnt look right. I was getting a halo around certain elements from the alpha channel becoming pre-multiplied (?), and one material for some reason came out alot brighter. I’ll maybe post a thread on this once I get a chance to check I’m not doing anything wrong.
It would be extremely useful, cos i guess lots of users will be revisiting render elements very soon. As far as it goes i havent had issues compositing layers but i must tell i havent explored all the possibilites render elements offer. Usually i dont have the need for so many layers, but we’ll see, maybe in the future i will!