SEUS PTGI E10 Dev News (Patreon)

Hey, everyone! Here's what's going on with the development of SEUS PTGI E10!

So, what you see above is a preview of some tech that I've been working on, regarding the GI denoising filter. 

In order to get more effective samples per pixel, I have designed a filter that, like most other denoising filters, utilizes information from previous frames. This temporal filtering is quite effective and common in games nowadays for various different rendering techniques and effects. However, it has an obvious downside: if you re-use information from previous frames, you introduce "lag". This can be seen in SEUS PTGI when, for example, destroying a light block, where a "ghost" image of the lighting is left on-screen, then slowly fades away.

I have been working on a big technical overhaul of the ray tracing and filtering in order to try to overcome this issue. In fact, this has been one of the most difficult problems I've ever worked on, especially considering how fully SEUS PTGI is already utilizing the resources that OptiFine provides! Whatever the solution, it had to be really lean.

The goal of this new feature is to detect when lighting changes on-screen, and force the temporal filter to discard information from old frames, so that lighting instantly updates.  This not only promises improved lighting responsiveness (like when blocks are placed or removed, or when mobs walk by, casting screen-space traced shadows), but also better lighting stability and filter quality when no lighting changes are occurring (since if no changes are happening, the temporal filter can allow itself to more aggressively use previous frame data). 

It's a simple enough concept, but it's been quite difficult in practice. Just as I was about to give up on it, I had a breakthrough that brought it to the point where it may be good enough to actually put in the next update! As you can see above, so far it's working fairly well! Though, do keep in mind that due to how OptiFine operates there will always be one frame of latency in the lighting data (you can see that happen when the door opens). But, lighting "ghosting" is significantly reduced!

Just like the existing filter design needed time to grow and improve, this one will as well, and the first release with this feature may be more of a step sideways rather than forward overall, but the potential is strong enough to explore and see what becomes of it! 

So, this will probably be the main new feature of SEUS PTGI E10, but as usual, there are lots of other smaller improvements coming as well. There are still a handful of things to fix with this new filter, so I can't predict for certain what kind of performance impact it will have, or when it'll be ready. Whatever the case, I'll keep you guys updated!