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Technical discussions => General discussion => Topic started by: rfollett on October 30, 2020, 10:27:42 am

Title: how stop edge white lines
Post by: rfollett on October 30, 2020, 10:27:42 am
so i have a simple plave for roads on.. This has alpha .. I have used defringe but still get issue round edges.. any ideas?

thanks you
Title: Re: how stop edge white lines
Post by: andy.engelkemier on November 02, 2020, 07:31:34 am
not enough information, so it'd just be a guess.
My first guess is that there is a fairly bright color in the environment behind there. So turn that on to see. Antialiasing is done based on an average of the values that make up a pixel. In the pixel it might be divided up into 16 parts to give you the edge that runs through the pixel. But the background makes up say 8 of the pixels? So you have your value of 35,35,35 (.13 float) averaged for the 8 from your part. But then you have a value of 3.5,3.5,3.5 float for the background. If that's 50/50 that averages out to be....2.275...which will show as just white.

You also may have that in the image if the alpha isn't quite right. Use the alpha in something like AE to see if it does the same thing there.
BTW, AE will let you control the alpha Separately for an image, allowing you to clamp that on it's own. I really with Photoshop had some of those tools for layer adjustments. But I get it, photographers might be confused why they would need to edit alpha channels of a layer separately. (That's Adobe's argument for most everything).

Also don't forget you can defringe more pixels. It works in a pinch, but doesn't work for images saved with soft alpha from things like a ground shadow. It'll really F that up.
Title: Re: how stop edge white lines
Post by: rfollett on November 03, 2020, 01:04:32 am
thanks Andy, I dont have AE.
I did use defringe but just 1 px.. maybe more..

basically it is a road cutout into a png... see attached