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.