Color remnants on edges of Anti-Aliased renderings.

So this problem has been bugging me for a while and I’m not sure if there is any ways around it.

Many times when I render sprites for a 2D game I’m working on, I use anti-aliasing to make the otherwise pixelly edges look smoother. But every time, I find the around the edges of my sprite, there are remnants of the “Background” color I set in blender (usually black or white)… This really bugs me because I don’t want a little line of white color around my sprites when they walk on black background… Or black lines around them when they walk in front of white backgrounds.

Is there any ways around this?

I hope that isn’t confusing, if you guys don’t know what I am talking about I could render some examples.


Are you rendering them out as png or something that supports alpha? I kind of guess that your image is not calculating alpha or utilizing alpha, and usually this is with stuff rendered to 'premul’tiplied… if you could indicate the actual image or show one, we might be able to help you with pin pointing possible solutions. As an example, when I am using the compositor nodes, sometimes I get those edges until I tell the specific node to calculate the alpha. Not saying that is what is happening, but maybe similar.

Hey Craig, thanks for your suggestions. Yes, I am using PNG format with alpha enabled.

I’m pretty sure I figured it out, although I think it’s something they finally added to Blender 2.57. Under the alpha settings you can choose Sky, Premultiplied, and Straight Alpha. They added Straight Alpha to Blender 2.5 which is exactly what I need, it uses no color from your “Background” color and just uses pure alpha.

I attached an example of the difference between using ‘Sky’ and ‘Straight Alpha’.


Nah, 2.49b had it, as well as many other releases before that I 'm afraid - could be that it is because the panel is different that it seems like it is new. Good that you got it fixed though :slight_smile:

Actually 2.49b did not have it. The panel looks very different, but I just checked, you could select Sky, Premul, or Key, and Key did not does the same thing that Straight Alpha does. I have tried to do the same thing before and I don’t think it was possible unless there was some other way I had no clue about.

My apologies, I thought it was like all the other name changes from 2.49b to 2.5x, where they changed the name but kept the same functionality.