VRay Light Texture Resolution Issue

[Dave Buckley]

Long time since I've been on these forums, so hi again.

 

I'm wondering if anyone else has had this issue.

 

I've setup a scene in VRay and setup my lights.

 

First I created a VRay Dome and assigned a HDR to the texture slot as per the usual workflow. I increased the texture resolution to 2048 for that light and ticked 'Use Texture'.

 

I then created a number (hundreds) of VRay plane lights. By default the lights have all set themselves to 'Use Texture' ticked on and Texture Resolution at 2048 as per the Dome Light. However there is no texture in the slot. Obviously because I only want the HDR on the dome light.

 

What I noticed was that even though the plane lights aren't using a texture, the settings 'Use Texture' being ticked and the resolution of 2048 on each light is having a huge effect on rendertime. My light cache was saying 40 hours.

 

I've since unticked 'Use Texture' on each plane light and reduced the resolution to the default 512 and the light cache has gone down to 30 minutes.

 

So ... should these settings be having any effect if no there is no texture defined for the light?

 

Is this a known bug? And does that resolution setting affect anything such as noise or shadows if there is no texture being used? If so I reckon I could set that value to 0 and save even more time

 

Cheers

[Chris MacDonald]

I believe that the resolution setting has nothing to do with the "backplate" that gets rendered in your image, and is the actual resolution for the lighting.

 

A lot of companies offer "blurred", or low resolution HDRI's for lighting and high res ones for background/environments/reflections, but VRay downsamples the HDRI on the fly (using the resolution setting) so that you can use the high res HDRI instead of having to downsample it or use a blurred one.

 

Having it set to 512 should be fine. Lower than that and you may find your lighting becomes more diffuse.

Edited April 18, 2013 by Macker

[Dave Buckley]

I understand how it treats the HDRI, but that's not my issue. The issue is that the setting was causing my render times to increase massively on lights that aren't using a texture i.e. my normal ceiling plane lights.

 

I'm yet to test properly, but essentially if you create a simple scene, add a plane light, turn on 'Use Texture' but don't specify any texture. And set the resoultion up to 2058 or whatever. Press render. Now render the same scene with 'Use Texture' unticked and the res set to 512. Does it render quicker?

 

I would have though these 2 settings would make no difference on the render time unless you actually place a texture such as a HDR in there. But my point is it seems to affect rendertime regardless of whether there is anything in there or not.

[Chris MacDonald]

Good question. I have 5 mins spare so I'll run a test.

[Dave Buckley]

Bear in mind, I had a scene with around 200 lights in it all set at 2048 resolution but no texture map assigned. The light cache was estimated at 40 hours. I unticked 'Use Texture' on all those lights and set the res down to 512 and the light cache completed in 30 minutes. I just want to do a simple test to be sure

[Chris MacDonald]

Running a test now, admittedly it isn't with 200 lights and a full on render etc, but I presume the problem is scalable. I'm doing it brute force/universal settings to rule out any GI bias.

[Chris MacDonald]

Okay, so the results are the opposite of what you've got. The one with higher (2048) samples rendered quicker than the one with lower (256) samples!

[Dave Buckley]

Interesting, i'm in VRay 2.3 at the minute. Maybe it's one of those that has an adverse effect depending on the volume?

 

Still nice to know it does make a difference when no texture is being used. Just which way ...

[notamondayfan]

I guess It's hard to compare different scenes as things like refraction could affect render times.

 

I might do a quick test tomorrow. Dave, I presume this was some kind of interior scene? Was the Vray light behind any glass? Also do any of the lights intersect any geometry?

 

Dean

[Dave Buckley]

It's a number of scenes, I have a huge development (5 buildings) each building is XRef'd into the scene file, the scene files contain the camera and lights only. The light setup of each scene is essentially a dome with hdri, then a number of plane lights (depending on what can be seen) inside the building to simulate the illumination.

 

The lights don't intersect any geometry, they just float slightly below ceilings around the perimeter of each floor and are positioned behind glass (think typical office building at night)

 

The key is that I didn't change anything other than those settings previously mentioned. The only light which actually has a texture map assigned is the Dome which has an .EXR assigned. I've never altered the dome light settings either. None of the plane lights have a texture assigned and never have. The only thing I changed is going from 'Use Texture' ticked with a res of 2048 (40 hour light cache) to unticked and 512 (30 minute light cache) on each light.

 

The plane lights were originally ticked and set to 2048 because max remebers those settings from the previously created light, and the dome was the first light to be created.

[Francisco Penaloza]

I think you should post this at chaos group forum Vlado for sure will jump with the right answer for this.

Now in Theory even thou there is not texture there VRay may be still sampling that light until your value of 2048, that in case of having a texture there time hundreds of lights, yes it will take a heck of a time to compute.

[Dave Buckley]

Definately. If that is the case, then i'd like to know what else it affects, i.e shadows and noise etc. if it doesnt affect anything and is purely sampling for the sake of sampling (just in case there is a texture) then surely we've all wasted tonnes of time on past projects by leaving the defaults at 512 rather than 0 ... Right?

[Francisco Penaloza]

Well as you mentioned now yes, I'll keep it in mind for sure

[notamondayfan]

Perhaps it's something that has stemmed from you first creating a vray dome light with a HDR. Perhaps then when you've created the new lights, some setting has copied over, perhaps even something to do with the HDR file.

[sheldor]

Definately. If that is the case, then i'd like to know what else it affects, i.e shadows and noise etc. if it doesnt affect anything and is purely sampling for the sake of sampling (just in case there is a texture) then surely we've all wasted tonnes of time on past projects by leaving the defaults at 512 rather than 0 ... Right?

 

Hello, did you find the answer to this question? It's really interesting phenomenon.

[paneli]

30 minutes to calculate lc?

I never want beyond 5 minutes in a very complicated night scene..

[Dave Buckley]

How big are you rendering your images at panibor?

[paneli]

Depends. 2.5k most of the time.

[Dave Buckley]

Cool well we're rendering 6 to 8 k hence the massive lc times