Basic question: Why is my .png-alpha channel black?

[justavisitor]

The alpha channel is transparent when I render .png's in Cycles.

But it seems to be black by default in Octane. How do I make it transparent?

On a related subject: The .png's I have rendered in Octane so far are slightly less sharp and have less contrast than images rendered in Cycles. Clean lines seem slightly dithered. Colors also seem a bit off; in Direct Light they're a bit too yellow, and a bit too red in Path Trace. But perhaps I'm missing some settings.

[Elonius]

I could be wrong but I believe black means transparency. It's like a float value where 0 = transparent(black) and white = opaque.

[justavisitor]

Thank you - do you know how to change the black into transparency?

I've tried every setting I can think of, including everything with the word 'alpha' in it...

[justavisitor]

I asked Octane's support and they solved the problem!

It's not automagical like Blender's Import Images As Planes which provides an instant Transparency function, but it definitely works.

Here's the correct node setup, in case anyone is interested (important: THe Gamma settings should be adjusted; particularly on the Octane Alpha Image Tex):

[mib2berlin]

Hey man was even to prepare a testfile for you.

Cheers, mib

[justavisitor]

Hey man was even to prepare a testfile for you.

Cheers, mib

Thank you so much! Don't worry, I always enjoy a nice alpha image.

The thing I didn't get is that it is necessary to have an ordinary image tex and an alpha image tex in order to render a realistic image, as opposed to a mask.