Weird dark patch in the reflection

[soulburn3d]

Got a strange problem here.

In the attached scene is a cylinder being lit by a single vray light. The material (vray material) has a dark diffuse, a white reflectivity, fresnel is set on to 1.2, and there's an output map in the environment slot set to super white. And when I render the middle of the cylinder has a large dark patch on it. Any idea what's causing this and how to avoid it?



- Neil

[cheerioboy]

I can't open the max file (I'm on max 2012) - but is it possibly the Cutoff? In your VRayMtl, under Options try changing the cutoff to .001 and see if that solves it.

[soulburn3d]

Bingo, that was it. It's weird, I would assume this would be a common problem for anyone using low IOR values, the threshold seems kind of high. Anyways, I'll set it low in my materials from now on as long as it doesn't increase rendertimes too much. Thanks for the help!

- Neil

[kosso_olli]

Mr. Blevins, is this you? Oh my god, you switched to Vray!

Just wanted to say thank you for your great cg education site. I learned a lot from all the articles over there.

[soulburn3d]

Thanks Kosso, glad you've enjoyed my educational material.

I don't think switched is quite the right word, as I don't plan on using it exclusively, but I am certainly adding it to my arsenal. In fact, from a time perspective, I'd have to label prman as my primary renderer since it's what I use at work all day, and I doubt Pixar will be switching to vray anytime soon But I have to say I've been really pleased with the level of support I've gotten from Vlado and the vray community on this board, I'm happy to be a part of the group.

- Neil

[Alan Iglesias]

Nice to see you here, Neil.

-Alan

[vlado]

Bingo, that was it. It's weird, I would assume this would be a common problem for anyone using low IOR values, the threshold seems kind of high.

Well, it wasn't high before all the gamma stuff started happening But yes, we need to adjust the default value.

Best regards,
Vlado

[soulburn3d]

Nice to see you here, Neil.-Alan

Hey Alan! Nice to see some old timers like me here too

Well, it wasn't high before all the gamma stuff started happening But yes, we need to adjust the default value.

Ya, gamma messes with everything Glad to hear it'll get adjusted.

- Neil

[pierrelemaux]

Hello,
I have this problem regulary but this time I can not solve it withe the cutoff parameter. Can you tell me how to fix this?
Thank you very much,
Pierre

[tooves]

Thanks Kosso, glad you've enjoyed my educational material.
- Neil

I'd just like to chime in and say your scripts and CG Education articles have saved me countless hours over the years so its great to see you playing with V-Ray and getting involved with the community. Cheers!

[tooves]

Hello,
I have this problem regulary but this time I can not solve it withe the cutoff parameter. Can you tell me how to fix this?
Thank you very much,
Pierre

[ATTACH=CONFIG]16090[/ATTACH]

Is that a bump map on the glass and do you have the problem if you disable bump?

[Morne]

If the mullion wasn't there, I would think it's a T-1000 coming through...

[pierrelemaux]

Yes it is.
I try to disable it but it doesn't change the bug. If i increase the cutoff parameter it grows the dark shape.

[alexyork]

double-check you don't have some overlapping/coplanar faces going on there.

[tashko.zashev]

Yes it is.
I try to disable it but it doesn't change the bug. If i increase the cutoff parameter it grows the dark shape.

[ATTACH=CONFIG]16094[/ATTACH]

If the solution provided by Alex doesn't help. Please try to simplify the scene and post a link, in order to see the whole setup.