[FEATURE] - Motion blur effect possible?

[ASchneiderBR]

Is your feature request related to a problem? Please describe.

No problem at all, just wondering if there is a possibility to have motion effect blur happening somehow in real-time? This would be great but very resource intensive, specially because we don't have access spatial motion vectors from a game, for example. I use this NLE plugin for years now, just love it - https://revisionfx.com/products/rsmb/. Not sure if this would be possible in real-time. Thanks!

[couleurm]

we discussed something close to that in #100, but it blends frames, but it does not do rsmb/flowblur style motion vectors

If I recall correctly some ReShade shader does this, look for "blur" shader, definitely possible to capture that in OBS, though you won't be able to use game capture

you might wanna try hacking by capturing whatever you're trying to record with mpv, and apply a vapoursynth filter or through ffmpeg's vapoursynth demuxer, use core.mv.Flowblur from mvtools and then record/output that some way to OBS

[FiniteSingularity]

I definitely want to improve this first go at a motion blur. I think the effect deployed in 1.5.0 is a fun effect, but doesn't really do the more useful effects that both of you want to see. I'll dig into some of these other shaders, and see what we might be able to accomplish in OBS.

[FiniteSingularity]

Just to explain how the currently implemented blur works. Many temporal blurs use a buffer of the past N frames, and average them in some way- either evenly weighted, or more likely some sort of exponential/gaussian decay. Unfortunately, for OBS this is not realistic, as the current filter is one of many other shaders that are being called to draw on the screen, and we very quickly would start to run into video memory and dropped frame issues.

The algorithm I implemented only uses 2 frames (the current frame, and the prior drawn frame) to estimate an exponential decay. Here is how it works:

The user sets the influence of the current frame- a value between zero and 1.0. Lets start with a very simple to calculate influence of 0.5. This means that the current frame consists of 50% of the color values, and the previous frame consists of 50%. So how does that give us an exponential decay? Lets walk through the first few steps.

When we render frame 1, 50% of the color comes from frame 1, and 50% comes from frame 0. So it would look like this:
F1_out = 0.5 * F1_in + 0.5 * F0 where F1_in is the un-changed input from the source, and F0 is whatever was output at frame 0.

Now we render frame 2, we take 50% of F2_in + 50% of F1_out. But remember what F1_out was? This ends up looking like:
F2_out = 0.5 * F2_in + 0.5 * F1_out
which is also: F2_out = 0.5 * F2_in + 0.5 * (0.5 * F1_in + 0.5 * F0)
which is: F2_out = 0.5 * F2_in + 0.25 * F1_in + 0.25 * F0

Following this logic, F3_out is:
F3_out = 0.5 * F3_in + 0.25 * F2_in + 0.125 * F1_in + 0.125 * F0

So as we move over time, the influence of the oldest frame keeps getting cut in half. If the user sets the current frame influence to 75%, the past frames will drop off much faster, and if the user sets the current frame influence to 25%, the old frames will stay much longer giving much more motion blur. (in the case of the plugin interface, the user is actually setting an amount which is 1.0-influence, so that larger values cause more motion blur).

The biggest problem with this method- because we are constantly using float multiplication at each step, error builds up. You can see this if you set the "Amount" to 1.0 and the clear threshold to 0.00%. You'll start to see errors in the color around where movement occurs. The clear threshold states that if a pixels value is within some percentage of the current frame pixel, set the pixel to the current frame and start the whole blending process over.

This is a really naive though efficient approach, and I'm very open to alternative ideas.

[couleurm]

yup the temporal blur filter doesn't fall under the category of frame blending (smoothie/premiere pro term) aka resampling in vegas pro terms or tmix in ffmpeg terms

I've seen a similar approach being used in minecraft motion blur mods

I suggest you look at how upgradeQ did it in their lua script: couleurm/smooth-mode#2

[ASchneiderBR]

Amazing news! I'm glad Finite liked the idea, really excited about it 😊 (I am the Brazilian guy who shows up now and then on your Twitch live streams haha)

Sadly, I don't have the necessary skills for coding but please let me know if you need any help or testing.

I believe this effect would be awesome to have, I can see so many ways of using it.

Thanks a lot, guys!