Arnold specular flickering

#1

Hi!

Im doing some animations with Arnold, ( im new to it ) but i keep getting a weird specular flicker that seems to happen only on the bevels, it also happened on some cilinders that where simulating wires. ive tried upping the specular in render globals but doesnt seem to do much, also tried with the arnols standard shader and with a blinn. cant get the flicker to go, could it be the geometry?

Here are some examples of what im talking about:

https://www.dropbox.com/s/z2mudifv4u8i1o7/eyecatchingSPECULAR.mp4?dl=0
https://www.dropbox.com/s/moicmftn3yqmjyv/onourway.mp4?dl=0

Thanks in advance!

Dave.

#2

only thing that occurs to me ( I only have a little experience with arnold ) is that your renders look too sharp for animation, fixing that might help. I’d use gaussian reconstruction filter and never mitchell of lanczos - they’re ok for stills but they create edge artifacts.

Are your models faceted? If they don’t have rounded edges, that could cause this

#3

Hi Dave,

Did you manage to resolve this? I have spec flicker and not sure on best approach to fix either.

#4

Hey DIngodunk, actually i didnt, so if you get a solution please share it here haha good luck man!

#5

Turn on the Clamp AA samples option in the Clamping section of Arnold and adjust the AA clamp value and Indirect Clamp value to get rid of highlights or spec flickering. Maybe turn it down to 2. And also if you AOVs in your scene then do not forget to turn the Affect AOVs option On as well.

#6

I started using Arnold a lot since this was posted and had lots of problems, incl. lots of specular flickering. Ridiculous amounts of minimum AA ( 1000 ) would not stop it.

One thing I found is that if you use the Metalness feature in the shaders, your specular highlight values go way higher than if you use straight specular ( increasing IOR to 8+ gives you a similar result to Metalness )

That gets even worse if you have guys applying both metalness and specular. That’s so wrong that the Arnold guys should be ashamed of themselves for not taking care of it. It literally doubles the amount of light reflected, which is about as anti-physically-based as you can get.

If you have flickering or noise problems, definitely look at how high above 1.0 your highlight values are going. Render engines & AA can only deal with so much.

EVentually I had to drop the Spec contribution in all the lights, because there were too many shaders to fix, all of which had 100% spec intensity. Try to keep those as low as possible too.