The the SDF or signed distance field effects filter adds inner and outer shadows, glow effects and outlines to any source or scene.

The filter can only be used with sources that contain transparent pixels (alpha channel) and do not fill the entire texture, as it operates on the boundary between opaque pixels and transparent ones, a common misunderstanding of this filter it seems. So if you use it on a fully opaque texture, there are no transparent pixels and it can't do anything. Once used on a transparent source, such as a chroma keyed webcam, or an image with a transparent background, the filter's effects become fairly obvious from tinkering with the controls however.

Note that the SDF filter can be quite GPU intensive so keep an eye on GPU usage in Task Manager or some other tool that can monitor usage, to ensure GPU usage of this effect is not overused as that can potentially interfere with games and/or OBS performance.