Noisy reflections from IES Lights

[isoparmesan]

I've been running into an issue with VrayLightIES paired with an IES profile from Kino-Flo. Basically, when the lights show up in a glossy reflection, they're very grainy unless I up the samples very high. If I use a vray rectangle light or dome light/exr map it works fine. I've messed around with the sampler settings quite a bit. The resolution on the lights themselves don't seem to have much of an effect (upped them from 8 to 64). My DMC is 1 and 12, with adaptive threshold 0.010. Is this an expected result? or am I doing something wrong?

Lowering the threshold/upping the max samples does get around the problem, but at a huge render time cost.

[isoparmesan]

Nevermind. It seems that the issue actually WAS the subdivs on the lights themselves. Set them to 100 and eased up on the DMC settings to account for render time. Problem solved I believe.

[isoparmesan]

Ok, so problem not really solved. For my last project (when I posted this) I had to switch to regular Vray Rect Lights because of issues with the Photometric lights. Now that I have some free time I'm trying to troubleshoot it again.

It seems that the only way I can get the VrayLightIES to show up nicely in reflections is to pump the subdivs way way up, and this is not necessary with the regular rectangle light. Right now I have a test scene open with a sphere and an IES light with subdivs set at 600 and it takes a 12-core Mac Pro and 4-core Macbook Pro 11 minutes to render just one glossy highlight on a sphere.

The other strange part is that the issue isn't present in the soft shadows cast by the IES light. I can get those to smooth out with the subdiv setting somewhere between 15 and 30.

So, is this just how the IES light works? In which case, does anyone use it in animation (my case). Or am I completely missing something?

I'm using V-Ray 2.40.02 and Maya 2015 Extension 1 + SP5 on Mac OS X Yosemite. I've attached comparison images and an example scene. Any hints would be greatly appreciated.

IESLightComparison.zip

[georgi.zhekov]

Hello,

There seems to be an issue regarding your case.

If you set the reflection glossiness for the sphere to something like 0.92 and then you lower the IES Light's subdivs to 64 - it should render a lot faster. I logged this case in our bug tracking system and our developers will looks into it.

Thank you,

[isoparmesan]

Thanks, at least I know I'm not crazy.

So, currently if I want to have near mirror reflections, I should stick to rect lights?

[isoparmesan]

I actually have another related issue/question.

Seems like IES lights are never actually visible to the camera. Is this also a bug, or is that normal?

[tashko.zashev]

I actually have another related issue/question.

Seems like IES lights are never actually visible to the camera. Is this also a bug, or is that normal?

They are just point lights with special light distribution and can't be viewed directly even with different shape modes.

[isoparmesan]

So, is this confirmed as a bug then? If I want to actually have an object that has mirror, or near mirror glossiness, I've been using a workaround where I apply a VrayLightMaterial to a cube that is the same size as the IES light that way it shows up as a highlight. It's not completely accurate, but it's a functional cheat.

Is this an issue in 3.0, and/or is the issue going to be fixed in 2.0?

[vlado]

It's not exactly a bug; the code works as it is meant to, but there is definitely room for improvement. The way IES lights are implemented right now, they don't have a physical geometry representation in the scene. Which is the reason why they are not visible to the camera, and why reflection rays do not hit them (they only produce specular highlights and these need really a lot of samples for nearly perfect mirror surfaces). This is the same in V-Ray 2.x and V-Ray 3.x; hopefully we'll get to rework this in one of the next service packs.

Best regards,
Vlado