I need to solve the following problem: do some anti-aliasing onto an image that contains rasterized "lines".

I have some post-processing effects that output super-thin (~1px) features such as silhouette-edges and outlines as shown here:

enter image description here

I tried with an FXAA shader I found online, which works fine if the line is at least 2px wide, doesn't work with 1px lines. I guess the edge detection method completely breaks with such thin features (also the common optimization to sample at the boundary of the edge won't work with lines).

How should I address this issue?

Is there a technique out there specifically designed to solve this problem?


1 Answer 1


A gaussian blur with a small kernel size, like 3, would blur the line into adjacent pixels and may be all that is needed.

There is a technique called jump flooding that will turn an image like this, even with very thin lines into a signed distance field. The signed distance field can then be used to recreate the lines at any thickness, with anti-aliasing. There was a paper written "Jump Flooding in GPU with Applications to Voronoi Diagram and Distance Transform" and there is an interesting blog post at https://bgolus.medium.com/the-quest-for-very-wide-outlines-ba82ed442cd9. The blog post is about generating wide outlines but it applies to thin lines and anti-aliasing lines as well.

One interesting thing about jump flooding is it allows for fractional pixel widths like 1.5px wide lines.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.