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

Posted: Mon Feb 23, 2015 7:44 am
by 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.

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

Posted: Tue Feb 24, 2015 2:51 am
by Elonius
I could be wrong but I believe black means transparency. It's like a float value where 0 = transparent(black) and white = opaque.

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

Posted: Tue Feb 24, 2015 10:36 am
by 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...

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

Posted: Tue Feb 24, 2015 10:44 pm
by 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):

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

Posted: Wed Feb 25, 2015 9:47 am
by mib2berlin
Hey man was even to prepare a testfile for you. :mrgreen:

Cheers, mib

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

Posted: Wed Feb 25, 2015 11:52 am
by justavisitor
mib2berlin wrote:Hey man was even to prepare a testfile for you. :mrgreen:

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.