grainy reflection/ flickering glossy

[king_max]

I'm having trouble with the attached scene. It's kind of a night scene with an illuminated christmas tree. Since there will be an animated camera in this particular scene, I need to optimize the render times as much as possible thus avoiding flickering. First I thought the reflection "dots" were caused by the preview render settings, but last night I rendered the scene with insane parameters (glossy at 40+, light subdiv at 48, IRR very high, LC 2000) and the problem was still present (see attachment). I'm thinking that perhaps the tree lights (it's a vray mesh light) that intersects with some of the geometry might cause the problem. Btw. this is the fastest method I found since using vray light material or vray standard lights greatly increases the render times. Any suggestions?

I forgot to mention that the scene is mainly illuminated with a dome light (low res diffuse HDR), a spherical vraylight and vray plane lights at the window openings (skylight portal)

[king_max]

Well, since none replied to this post I'll assume I ether posted it in the wrong section, or I wasn't so clear about what's bothering me.
I'll share with you what I've discovered to be the source of my problem.
Small very bright lights or light emitting objects that are visible to reflections tend to create small grainy dots on any fairly glossy surface (i.e. glossiness 0.8 ). The situation doesn't change at all even if I put 100 glossy subdivisions in the particular material, nor does it change if I use extremely high GI settings. The only way is to turn off the reflection visibility of the lights/light objects. But then I lose all the "highlights" on the tree decorations.

I'd really appreciate if someone gave me an advice since I have a deadline in app. one week.

Thanks in advance.

[Morne]

maybe try ticking "interpolate" under your reflection in the material
under reflection option see that the settings there corrospond with the settings in your GI

nice image by the way

[king_max]

Glossy interpolation is not an option since this is not a still image. Initially I even considered animating the intensity of the light source coming from the right to achieve a fireplace lighting effect. Obviously it's out of the question.
I'm just trying to figure out if there's a "magic button" that solves the issue or It's just this particular scene case that requires sky high settings and glossy interpolation to get a clean result.

thanks for the positive comment.

[Dariusz Makowski (Dadal)]

Break it on layers maybe.

Do manual comp guide, see which layer exactly is causing the flickering. Then u can either smart blur it or see if u can find the way around it.

[gimiky]

are you rendering with sub-pixel mapping enabled? if not, enabling this might dull some highlights slightly but it tends to resolve bright highlight grain.

[king_max]

Clamp output and sub-pixel mapping were on from the beginning to avoid flickering in the first place. From the day I wrote this thread I've tried different GI combinations and settings. Using an adaptive dmc sampler of 1-10 and quadratic image filter dulled some of the reflection. Anyhow, I've broke the render in 2 main passes, one without the tree lights, and one with the tree ornaments only (light reflections on). I plan to blur the reflection pass of the leather chair in post.

Thanks for the support.

[simmsimaging]

Just curious if you tried it with GI caustics turned off?

[king_max]

Reflective GI caustics are turned off by default. I won't turn off the refractive GI caustics since I have a glass material on the windows. Anyhow, refractive GI caustics shouldn't be the cause of the problem.

[joconnell]

Might be worth excluding the windows from casting shadows and GI entirely? If the light outside has a clear run in through the window it might make your sampling a tiny bit easier?

[Dariusz Makowski (Dadal)]

Have you try maybe to find the problem on layers?

[king_max]

As I said earlier, I've already found what's causing the problem. If I turn off "reflection" in the lights, the artifacts disappear, obviously loosing the real highlights in the scene. Excluding the windows from the GI would probably smooth the GI a bit, but wouldn't solve my problem. The GI solution is pretty clean in the scene. Anyway, I've already sent out the animation as it is.