very slow glossy reflections

[Hos]

I am working on a animation project which takes place in a dark parking garage. The garage has a multiple of lamps that are reflecting in the floor.
These lights are basically cylinders with a shader with the self illumination on a value of 500.
Rendering 1 frame of the garage will take about an hour on 720p and I still have a very grainy render.
After a lot of testing I found out that the problem in this scene, is mainly the glossy reflections.
I made a test scene to demonstrate the problem. After trying a lot of different settings I got the best results by using the adaptive dmc sampler on 1-4 and ramping up the glossy samples on the floor shader to 1000.
But it still takes about 33 min to render and the result is still grainy.
Can someone maybe give me some advice to get better results? I tried a lot different settings, but maybe I still lack the knowledge of the renderer to get good results.
I am rendering on a i7 4930K with 6 cores @ 3.4Ghz and with 32gig ram.
And I am rendering with vray 3.0 beta, I also tried with vray 2.4, but I get worst results with that.
Maybe an unfair comparison, but I exported the test scene to the octane renderer and with similar settings it took 6 seconds to get the same result as the render below.

this is the test scene (maya 2014) I have being using.
vray_glossy_refl_test.zip

[joconnell]

Your test scene is a tonne of area lights and not cylinders, correct? The attached file has only a flat lambert material on a plane, a load of lights and a camera looking down over them - could you re-check your scene? Also if you upload a raw light, sample rate, specular and reflection pass we can have a better look.

In terms of huge amounts of lights, there's a new feature in vray 3 being worked on to deal with large amounts of area lights that should give you big benefits.

[Hos]

I am sorry, I attached the wrong file for some reason. I edited my post with the right file.

[joconnell]

There's a few things in your scene causing issues. One is that you've got some incredibly blurry reflections there which I presume is an attempt to get a certain look / spread in the reflections. I think the light objects that you're trying to reflect are incredibly small though so the blurry reflection samples keep missing them every time. Sampling wise your scene had the dmc noise threshold set to 0.05 which is going to be quite noisy.

I'd say you'll struggle to get a result doing a garage this way, you're better off using lights for the light sources rather than making mesh objects - they'll only cast reflections and not any actual light, unless you turn on global illumination, and that's a bit of a round about way of getting light into your scene. Here's the test scene with a few changes. Lights in instead of the geo objects, your blurry reflection made slightly sharper (gives the floor reflection samples a better chance of hitting the very thin light objects) and some sampling tweaks.

vray_glossy_refl_test_edited.zip

[Hos]

Thanks Joconnell, for taking the time to look at my scene.
I didn't thought speculars could be such a good replacement for reflections.
After changing my scene to use only the speculars of the lights and not the shaders, I still have a few problems with the scene.
The lights also cast a reflection but a very dim one and in my scene the lights are a lot stronger then the lights in your test scene.
If I set the light multiplier in the test scene to 1000, then the rendering is a lot more slower and then you'll see the grainy reflection of the light.
Do you know why lights cast both reflection and specular? And how can you turn of the reflection of the light? Turning off the reflection in the light settings doesn't work.

[svetlozar.draganov]

Could you please clarify with what versions of Maya and Vray the scene is created.
I've just run a quick test with Vray 3.x official beta and Maya 2014 and I got the scene rendered in 13.8 seconds.

[Hos]

Hi Svetlozar,
The edited version of my test scene from Joconnell, also renders in a few seconds for me, but the original test scene takes about 33 min on my pc.
I used maya 2014 extention servicepack1 and vray 3.05.01 to create the scene.

[svetlozar.draganov]

I have actually used the scene from the first post, which is the original scene I think.
However I have used Maya 2014 only , no extension service pack.

[Hos]

That is interesting. But are you sure? Because the name of the render you posted, has the name of the edited scene in it.
Are there area lights in the scene you rendered or only objects?

[ivaylo.ivanov]

As joconnell said... If you need to put 1000 subdivs (this is 1000000 samples), you are doing it wrong

[svetlozar.draganov]

Please excuse me, I have downloaded the modified file not the original one.
The issue like joconnell mentioned is related mainly to the very tiny light-objects in the scene and the fact that the floor is very glossy.
I couldn't propose anything different than joconnell's workaround so far.