Black spot error with Specular?

[ASyme1]

Hi guys-
I'm wondering if any have seen this before. I've got a simple wood table top with a little spec. It's a glossy material. Basically, a wood map and some spec. Super simple. However at certain angles (Low) it renders with a solid black crescent shape at the rear. See attached. Notice that a render using a diffuse material renders fine. Of course I don't want it totally diffuse. I need the spec.

Thoughts?
Thanks
Alec

[profbetis]

Could be a smoothing issue or ray_epsilon, check to see if those are the culprits

[kavorka]

looks like smoothing, I like to extrude my top face and scale in. Rinse and repeat till you have a couple edge loops on the top "flat" plane.

This is a problem with Octane when rendering objects that don't have a lot of polys.
If you want to quickly test if its the culprit, turn off smoothing on your glossy mat. If the black goes away, you need more polys on the top.


Edit: On second thought, if that was the problem, it would be on both the glossy and diffuse mats. Unless you turned off smoothing on the diffuse.

So, it might be the scale of your scene is too large (sometimes caused when exporting). try scaling down by a factor of .1 and see if that fixes it.