Large scene flicker

[stevesideas]

I have a large scene that I'm rendering. There seems to be a lot of flicker when rendering using BF/LC. Do I need to scale the scene down in order to stop this ? The unit I have flying in is: 204900.2344 meters from the origin. Is there an easy way to scale down the whole scene if I need to do this ?

Basically, a helicopter is flying over a landscape and coming in to land. There is lots of flicker...bright reds (looks like from the exterior helicopter paint) that is GI reflecting into the cockpit. Not sure how this is happening other than a GI issue. The helicopter is moving quite fast too.

[stevesideas]

Okay. I've merged everything into a new scene where the scale was adjusted. Now the helicopter is only 1500m from the origin.

Still I have flickering.

I've overridden all materials with a basic 128RGB material. Still I have flickering. Not sure what is going on here but I'm running out of ideas and need this sorted for a render.

[Morbid Angel]

Can you show what sort of flickering?

[stevesideas]

I'll upload a short sequence when I'm back in the office tomorrow.

I'm going to test the geometry and also re-create the sun and dome light tomorrow. I did a previous scene with pretty much the same set-up (a few months ago) and everything was fine.

[jacksc02]

try adjusting the secondary ray bias to something like 0.01
Also are you using adaptive lights? or full evaluation?

[stevesideas]

Full evaluation as far as I'm aware. I only have a vray dome light and a vray sun in the scene.

[stevesideas]

I'm trying without probalistic lights. I've altered the secondary ray bias but the only reason for doing this normally is because of overlapping faces which I have none of in this scene.

[Zdravko.Keremidchiev]

can you send us a stripped version of the scene or at least the animation so we could have a look?

[stevesideas]

Here is a short render of the issue. I'm doing a new render now but really ramped up the lightcache. It was on about 2500 for the flickering preview. It's now on 3500. Maybe I should go even higher, what do you think ?

I've also noticed another issue. The camera and the helicopter is linked to a control point yet the camera in relation to the nearby helicopter seat still wobbles slightly. I'm thinking this is something to do with scene scale as I don't think I've experienced this wobble before on smaller scenes. Probably the reason why the flickering is occurring.

I'll see if I can send over a version of the scene shortly. Cheers

https://youtu.be/w89ANlwMqWE

[stevesideas]

I've put the LC to 5000. Seems high to me but if it stops the flickering then great.

[anthonyh]

hi,
the flashing looks like light cache problems to me, have you tried bf/bf just to make sure ? do you have any standard materials that might cause an issue ? standard self illuminated materials can cause issues.
since you don`t seem to have any animated objects and the camera looks static maybe you could prerender the lightcache on flythrough ?
possibly animate the scene around the helicopter instead maybe ?

i`ve had issues with helicopters and scene scale too (in particular with motion blur) if the scene scale is too large then it can cause problems ie if the helicopter is `technically` moving at warp speed across the scene. even if the camera movement is relatively small in relation to the visible animation vray (or max?) seems to interpret this movement in total with the movement within the scene. i was told about motion blur that it is working as intended(although it looked darn weird to me). likewise an impossibly small scale scene in max can also start to `judder` as the scale can`t cope with being that small. max has always had issues with scene scale extremes. eg the viewport is still terrible with large/small scenes, faces showing incorrectly by depth etc.
cheers
anthonyh

[stevesideas]

Yes, it was lightcache after all. I had to raise it to 5000. I think it must be because of the fairly large distance the helicopter is travelling.

The previous scene had the helicopter start much closer to the end destination so I guess that was why LC could be lower.

Vlado, do you think this might be the reason why ? Would LC need to be higher if the camera travels over a larger distance ?

I've not had issues with motion blur although to be honest I'm actually only blurring the rotors. Nothing else needs to be for this scene. Ideally I would have the exterior motion blurred but the extra time doesn't warrant it for me.

Cheers

[Zdravko.Keremidchiev]

Most probably the reason is the distance that the helicopter travels and the large windows through which the LC rays escape out in the environment. We could confirm this if you send us the scene so we could test it further.
Does the large LC value affects your render time much? You can try BF/BF instead.

[stevesideas]

The LC does take more time but I think it's not too extreme. I'll send a stripped down version when I get the chance. Cheers