View Full Version : LW 2018 is this a bug?

01-07-2018, 02:56 PM
OK I set up a basic ball head with fiber fx hair which is black so diffuse is turned down low, background lights. With gi on and off everything looks fine. Now add an hdri background environment and the hair is rendered but covered in pixel dots like dandruff. It only does this when using an hdri environment. What is causing this?

01-07-2018, 03:02 PM
Here is what I mean.

01-07-2018, 03:09 PM
This is not a bug, this is a sampling/aliasing issue, and one of the most difficult situation in CGI: small features (Hairs), HDR lighting and high surface specular response.

You'll have no choice but to lower the specular response of your material, gather enough (a lot of) samples (proper antialiasing settings, min/max/threshold/filter/filter radius) and perhaps/ultimately go for HDR limiting and/or filtering.

-- update --

I just saw your image, don't tell me you use Gaussian 0.5 ? ^^

-- update --

To support the fact that this is not a bug, you should be able to get this kind of results:

But this is not free, this one took 30m21s on a i7 980 3.33GHz 6 Cores

01-07-2018, 03:11 PM
I've now found out the cause. I had glossy reflections ticked in shading model. Renders OK now. Been searching my settings for hours to track it down.