Noise changes every frame =(

[cecofuli]

Hello,
as in the title, I'm rendering a short test (1080p). Outdoor, with grass and DOF.
After 50 passes (40 min) the rendering is good enough, but in the background, where the DOF is strong, there is a flickering cause the noise pattern changes every frame.
In VRay we have the option called "Time independent",

Time independent - when this option is On, the sampling pattern will be the same from frame to frame in an animation. Since this may be undesirable in some cases, you can turn this option Off to make the samping pattern change with time. Note that re-rendering the same frame will produce the same result in both cases.

I think Corona need the same option!

[Ondra]

are you using PT+PT? If so, this should be enabled by default

[cecofuli]

MM... no, I use PT+HD!
Is it possible add also for PT+HD? Obviously. cause PT+HD is faster!

[cecofuli]

--- DOWNLOAD ---
This is a video where I show how Time independent works.

[Ondra]

it would be possible only when reusing a single HD cache

[cecofuli]

So, because my sun changes position, I cannot use a single HD cache =/

[racoonart]

it would be possible only when reusing a single HD cache

Worth a try if it's easy to implement :)

[cecofuli]

But, if I remember correctly, in VRay, if I use BF+LC I don't have this kind of problem, even if I had a new LC each frame

[cecofuli]

Same problem with PT+PT  =( ...  Here two frames.

[cecofuli]

Same problem with PT+PT, without DOF, with crop area (top left, near the rocks. Flickering with 100 pass!!!

In this video (with VRay) with multiscatter I hadn't any problem with grass and flickering =(  (DOF in post)
Maybe some problem with AA?

But, in this video, only camera moved. In this Corona test, both camera and sun are moving.

[Ondra]

what random sampler are you using? Or better yet, just upload me the scene ;)

[cecofuli]

5D High-D +PRNG

I tried with CROP with 200 passes, and it looks, obviously, better. But the rendering time will be x4. So, from 40 min, I'll go to 160 min per frame at 1080p! Maybe this is the only solution: wait! =)
About the scene ok, I clean up it and I'll send you.

[cecofuli]

Ok, after some frame at 1280 with high settings (PTS 8 ans 150 passes) flickering still here. Look at the sequence. I don't know what can I do =(
I think it's AA problem, but I'm not 100% sure.

[maru]

You are referring to that noise on grass in the background?

Are these grass clumps the same models as grass in the foreground? I think the problem is there is so much geometry and shadows. Maybe try rendering it with pt+pt, pts 4. There isn't much visible GI here, you mainly need smooth edges.

[Ludvik Koutny]

i really do not think it is a bug. In foreground, you can see that shadows move across grass blades and it causes some rapid brightness changes on many spots. In background, same thing happens but on a lot smaller scale.

I would try following, just for sake of experimenting:

Make sure you do not use PT+HD. In this scene use PT+PT. There is really no reason to use PT+HD in this scene.

Set PT samples to 3

Set light samples multiplier to 1

Change AA filter from tent to Gauss.

[cecofuli]

Rawalanche, same problem with your setting.
I think this is a limit for Corona =( small objects with hight detail isn't able to render without flickering.
I'll make a sample scene fro everyone as soon as I can.

[cecofuli]

Here a simplified scene (with CoronaScatter) and clay material. Same problem. I don't know ho render this scene without flickering :/

[maru]

Are you sure it would be possible to render it without noise in vray? There is an animated sun in this scene so there are lots of subtle changes in that distant area. It's hard to imagine for me not to get animated noise in this case. You would even get noise if you recorded it with a camera in real life. :)

[maru]

Ok, I removed animation of sun and camera and now there is completely no noise in each new frame. You have to do the same or make the movement of sun/camera much much slower.

[Ludvik Koutny]

Ok, I removed animation of sun and camera and now there is completely no noise in each new frame. You have to do the same or make the movement of sun/camera much much slower.

Unfortunately that is not really a solution :) If he wants camera and sun moving, then he should have it. It is something that needs to be fixed from corona's side, not by restricting what artists can do.

[maru]

Yes, I know. But it looks like it's more of a feature than a bug. You can also see it in the grass in the foreground - shadows moving between individual grass blades. Same happens in the background but it's much more dense. I can't imagine how this could be overcome in vray or any other renderer.

[Ludvik Koutny]

Yes, I know. But it looks like it's more of a feature than a bug. You can also see it in the grass in the foreground - shadows moving between individual grass blades. Same happens in the background but it's much more dense. I can't imagine how this could be overcome in vray or any other renderer.

Yes, i wrote exactly the same thing earlier. Yet, i believe for example Vray would handle this case without any significant problems ;) So we need to make sure corona can too :)

[Ludvik Koutny]

BTW, do you use buckets or progressive?

[Ondra]

i would really like to see vray in this scenario. It is impossible to keep the same noise and do the optimal light sampling when lights change. This is not a bug and I cannot fix it...

[cecofuli]

This is some frames with VRay. I think I made a very hard scene ;-)

[Ludvik Koutny]

try to make a region of same size and render it for same time with same materials using both corona and Vray. I am very curious which one will win :)

[cecofuli]

From my fast test, VRay is better. The noise is more "stable".
In my old message you have the Corona version.
If you want to play, here the VRay version :)
Sorry for the file quality/organization. It was just a fast test!
PS: You need  VRay and multiscatter.

[Captain Obvious]

Random noise is supposed to change for each frame. Noise generated by screen coordinates only will look like it's sliding over geometry as the camera or the geometry moves, and generally looks shit. It's also impossible to properly filter out in post using motion vectors or optical flow techniques. If you're using Fusion or Nuke, I can probably point you in the right direction. For After Effects, your options are more limited.

Corona looks like it's doing things right.



The problem with the noisy DOF is something that will need to be solved with either noise reduction in post or better adaptive sampling in Corona.

[Ondra]

the idea is that locking the noise pattern is an OPTIONAL feature. Sometimes, it really looks much better than temporaly uncorrelated noise. Just set random seed to 0 and you have uncorrelated noise every time ;)

[Captain Obvious]

the idea is that locking the noise pattern is an OPTIONAL feature. Sometimes, it really looks much better than temporaly uncorrelated noise. Just set random seed to 0 and you have uncorrelated noise every time ;)

Yeah, I'm all for having it as an option. Just make sure it defaults to off. :) In modo, it defaults to on and sometimes I forget to turn it off. Mumble, grumble.

[Ludvik Koutny]

the idea is that locking the noise pattern is an OPTIONAL feature. Sometimes, it really looks much better than temporaly uncorrelated noise. Just set random seed to 0 and you have uncorrelated noise every time ;)

Yeah, I'm all for having it as an option. Just make sure it defaults to off. :) In modo, it defaults to on and sometimes I forget to turn it off. Mumble, grumble.

Actually, i hope it remains on by default. Static noise is a lot less distracting than a moving one, especially on very thin lines, where it can make hell once you have your sequence rendered and realize you wanted to turn it on. In production, a lot more people will want to get pictures as clean as possible, rather than rely on postprocessing denoising.

[Captain Obvious]

Fine, let's agree to disagree. :-)

Methods like this¹ basically only work if your noise changes from frame to frame.

1:  http://www.juvano.com/Deflickering-with-Velocity-Pass

[racoonart]

Methods like this only work on a fraction of real production scenes anyways ;)
My opinion: ON by default.