specular samples PBR - specular flickering

[teapot]

Hello,

How to control specular samples?

My actual workflow to control diffuse/specular samples:

create area light

position it

then turn off specular contribution and set "sampling quality" as is it in most cases

then copy the same area light and turn off diffuse contribution and turn on specular contribution

set sampling quality to minimum 2

without those steps I get specular flickering with displacement materials [specular noise?] and to completley remove it I would have to set global samples to 2-128 and pixel samples to 14x14. With 2 area light instead of 1 [diff and spec contributions: sampling quality increased] I have pretty clean renders with 8x8 and 1-18 global samples = quicker render.

The only bothering thing is that I have 2x more lights and it takes some time to set and organize those.

example:

[from 0:20 to 0:22, you can see random white dots in the background].

Arnold renderer [which is pathtracer as mantra is] gives you ability to set every type of sampling.

Edited June 24, 2013 by teapot

[symek]

If you could prepare very basic scene, someone will help you to get rid of a flickering. The thing that comes first is Minimum Reflection Ratio on Mantra ROP. From the help:

Enables a minimum amount of secondary ray tracing even when the surface bsdf reflects only a small amount of light. Normally, when mantra encounters a surface that reflects only 10% of the incoming light, ray tracing will be optimized by sending 10x fewer secondary rays - potentially leading to unwanted noise in the image. Increasing the minimum reflection ratio will ensure that the specified proportion of rays are traced as a minimum even for surfaces that have a low reflectivity.