Multiplied alpha

[LeSill]

Hello, folks.
I'm rendering some packages, and I need to render the packages and shadows separately before composing them in Photoshop. I had an issue with the alpha on the package's edge. The anti-aliased edge does not keep the few pixels with alpha, but instead multiplies them immediately with the the white background. It causes the problem with the white edge shown in the photographs. Is there a method to store the few pixels with alpha so that I may insert any background behind the package without a white border?

[BigAl3D]

The first thing I see is the package is not sitting on the plane below it. It is floating. Second, when dealing with pixels, there are some angles of edges that need more passes and anti-aliasing. First, drop that package down to actually sit on the plane and render that.

[LeSill]

Hi,
The edge of the model does not rest on the ground. The bottom is slightly bulging. I want to make it as realistic as possible. I had a similar issue with Octane, which is related to PREMULTIPLIED/STRAIGHT alpha. It is clear from the attached image. The white edge should not be there. It's not only at the bottom; it's everywhere.

[BigAl3D]

The only other thing that comes to mind, and it's a C4D thing, is if you're using a Sky Object and saving with alpha channel. Put a Corona Compositing Tag on the Sky and UNcheck Seen by Camera.

[burnin]

tho you don't need comp. tag for that, disabling object's direct visibility is fine // uncheck "Visible Directly"

[piotrus3333]

is the image you attached a crop from your render?
are you rendering on white background??

[LeSill]

The image is a Photoshop composition. The object was rendered with alpha and composed with the background in Photoshop. The object sits on a plane, and in addition to standard lighting, I used HDRI/SKY lighting to create ambient lighting. I will try to disable visibility of the sky. It might help.

[piotrus3333]

The image is a Photoshop composition. The object was rendered with alpha and composed with the background in Photoshop. The object sits on a plane, and in addition to standard lighting, I used HDRI/SKY lighting to create ambient lighting. I will try to disable visibility of the sky. It might help.

black background is a must.
also look at photoshop settings and make sure alpha you are using is saved correctly (for example by default corona for 3dsmax saves alpha to integer colour file formats with wrong gamma - attached)

[LeSill]

Thank you for the tips. It looks really promising. The EXR format, in particular, appears to provide a simple solution to the problem.

[LeSill]

I tried saving the image as 16-bit EXR (it's a shame we can't save CXR 16-bit from VFB) and opening it in Photoshop with the EXR IO plugin, but it always opens as 32-bit, so any conversion to 16 or 8-bit affects the colors. It is a little irritating. Is there a workaround?

[lollolo]

Linear 16-bit EXR will be treated as 32-bit in Photoshop or Affinity Photo. This is expected.

You could do everything in linear 32-bit mode (which I like the most) or convert it to 16-bit.
I can't give you advice for Photoshop, but you should find some tutorials on Youtube how to do it.