Render Mask

Hello Everyone,

After a render, if I press the a key, I get a pure black and white, the sky or background being black. How do I save this image? All of my attempts so far (F3) have saved the image as rendered, not the pure black and white.

I would like to use this as a mask for some post pro.

Thanks for your time!

the “a” key shows you the alpha mask of the render. The easiest way to save the alpha mask is to use composite nodes. Just open a node window and connect the renderlayer node alpha output to the composite node image input. toggle Do composite and hit render and you can then save it


The first time I tried it, I got a completely black render…then I found a loose nut behind the keyboard, re-read the instructions, tried again and it worked perfectly.


Actually, if you use a format (such as .tga) which saves the alpha channel, too, then you can easily save the image as rendered. You automatically carry the alpha channel with that image into your favorite image editor. No need to save masks seperately.

Even if you would like to have the B&W output, I’d recommend using the rendered output, simply add a black Background and make the rendered image plain white while keeping the transparency. That makes like 3 or 4 clicks in photoshop.

Edit: Heh, it seems to be too late already…

You always have to use an image-format that includes the alpha-channel; some formats don’t! And then, you have to request that it be generated.