There is a little bit of info in the docs about this:
“Temporal Anti-Aliasing or Why the GBuffer Jitters”
Temporal anti-aliasing is a unique UE4 feature that greatly improves image quality with a very moderate performance cost.
By default, a post process material is inserted in the end of the post processing graph (after tone mapper). This means you get the final LDR color after tone mapping, color grading and after the temporal anti-aliasing was applied. This is the best spot for many simple post processing effects - for performance and ease of use.
Here you can see how we used the custom depth input to visualize a silhouette around specific objects:
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Notice that the former image has no anti-aliasing on the silhouette but in motion you also would see the silhouette jittering around 1 pixel. This is because temporal anti-aliasing moves the rendering of the whole scene by a sub pixel each frame. Multiple frames together are getting combined to produce the final anti-aliased image. We can however move the material to an earlier spot in the post processing graph to fix this issue.
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Try set this to an earlier moment?
