OTOY Forums

Hi everyone.

Let’s discuss how to create a clear alpha map. Now I am working on a project where I am rendering separate parts of the interior and after I am stacking them in Photoshop. The SilverwingVFX video explains that the best way to get a clear alpha map is to use None mode for setting Premultiplied alpha. But I have faced a bug or maybe it is a feature. If I render an image in Live Viewer and Save it with the setting Premultiplied alpha: None then I get a clear result. There is an alpha map without a grey border.
If I use Picture Viewer of Render Queue for batch rendering it works differently. With Premultiplied alpha: None I get an image with a black border. I attached some examples below. I want to find out how I can get an image with a clear alpha map from Picture Viewer or Render Queue as the image from Live Viewer.

Updade: Link to .psd file included layers.

Live Viewer save settings:


Good render with a clear alpha map saved from Live Viewer:


Good final image stacked from the layers saved from Live Viewer:


Picture Viewer save settings:


Bad render with a black border saved from Picture Viewer:


Bad final image stacked from the layers saved from Picture Viewer:

Save it from the Render AOV Groups tab in Octane Renderer settings, instead of the Picture Viewer.

Hi Jayroth2020!

That's exactly how I do it, below are my save settings.

Disable the Save option in the left panel

It didn't help:((

Then submit a ticket to [email protected] so we can take a look at your scene. Be sure to do a File > Save Project with Assets... archive the result and send it in.

As I reported in the support ticket, you need to enable Save Beauty in the Render AOV Group tab, and disable the C4D Save control.

I noticed, the problem can be with the way your compositing software interprets the alpha, rather than how Octane rendered it out.
For example, After Effects by default interprets EXRs with straight Alpha as having a premultiplied one, resulting in grey borders.
You always have to tell AE manually to interpret them as straight.

henningricke wrote:I noticed, the problem can be with the way your compositing software interprets the alpha, rather than how Octane rendered it out.
For example, After Effects by default interprets EXRs with straight Alpha as having a premultiplied one, resulting in grey borders.
You always have to tell AE manually to interpret them as straight.

Isn't there a flag in the exr format which should be getting set so other apps know how to interpret the alpha?

Hi,
the Premultiplied alpha option was part of the Camera Imager node in the past, now it has been moved to Render settings/OctaneRender/Main tab: ciao,
Beppe