Vray Sun too bright

[thomascoote]

Hi all,

 

I've recently adopted linear workflow, and I'm loving the control it gives me in post production. I'm making sure everything is physically accurate, including light sources having correct lm values and the physical cam having correct exposure settings for the scene.

 

Everything is fine lighting wise, except the sun/sky. It's ridiculously bright unless I bring the multiplier down to something crazy like 0.01. This doesn't seem right to me, and it would make sense to keep it closer to 1 surely?

 

I just don't really understand how everything else seems to be coming out perfect except for the brightness of the sun and sky. Anyone have any insight into this?

 

Thanks,

[Dave Buckley]

Would need to see the scene, the other light settings and the camera, but I'd probably expose to the sun first. Turn all other lights off, then expose for the sun, then go from there. But you could just turn the sun down, that's fine too. Use the frame buffer exposure controls to balance the highlights? just don't get too hung up on it being 'perfect' just set it to whatever looks right. if it looks right it is right

 

I've learnt over the years to just tweak my lights to whatever I like. Things vary so wildly, especially when using HDRI's. Sometimes I do reduce my sun. But who cares, as long as it looks the correct brightness in the final image right?

 

By trying to leave everything at 1, aren't you reducing the marvel of 3d by stopping yourself using the full power of it. This is where we have the advantage over photographers, we can just turn the sun down, they can't.

[thomascoote]

Would need to see the scene, the other light settings and the camera, but I'd probably expose to the sun first. Turn all other lights off, then expose for the sun, then go from there. But you could just turn the sun down, that's fine too. Use the frame buffer exposure controls to balance the highlights? just don't get too hung up on it being 'perfect' just set it to whatever looks right. if it looks right it is right

 

I've learnt over the years to just tweak my lights to whatever I like. Things vary so wildly, especially when using HDRI's. Sometimes I do reduce my sun. But who cares, as long as it looks the correct brightness in the final image right?

 

By trying to leave everything at 1, aren't you reducing the marvel of 3d by stopping yourself using the full power of it. This is where we have the advantage over photographers, we can just turn the sun down, they can't.

Thanks for that, in the end I did manage to get it looking right with lowering the intensity right down and having a good fiddle with some exposure settings.

 

With leaving everything at 1, I thought that using LWF you'd also keep the intensity of the sun to default too and adjust in post (I do the vast majority in post after learning how to composite and exposure correct 32bit EXRs), it was just the direct light from the sun was bleaching my lighting and gi pass so assumed I was correct to leave it at 1 but was mission some settings somewhere.

 

I had success in another scene I worked on earlier assigning the sun as a lightselect pass and blending that with my light layer as a difference blend at like 98% opacity.

 

Linear workflow is great, I'm loving this new way of working, guess I've just still got some teething problems

[Dave Buckley]

meh, lwf is overrated, i just do whatever looks good to me. Who cares as long as the person paying for it likes it.

 

Nobody truely uses LWF anyway, as soon as you download a texture from the internet you're not using a full LWF workflow anyway. Don't get me wrong it's good for rendering etc. But don't get too hung up on it. What's the difference between adjusting in post and adjusting in render? aren't you essentially doing the same thing? You render an overbright image and turn it down? Isn't that the same as turning the sun down? If you're rendering 32-bti you'd still get flexibility in the exposure anyway.

[thomascoote]

meh, lwf is overrated, i just do whatever looks good to me. Who cares as long as the person paying for it likes it.

 

Nobody truely uses LWF anyway, as soon as you download a texture from the internet you're not using a full LWF workflow anyway. Don't get me wrong it's good for rendering etc. But don't get too hung up on it. What's the difference between adjusting in post and adjusting in render? aren't you essentially doing the same thing? You render an overbright image and turn it down? Isn't that the same as turning the sun down? If you're rendering 32-bti you'd still get flexibility in the exposure anyway.

Very good point actually. I've just been getting hung up on sticking to real world values as much as possible I guess and wasn't sure if 1.0 was a real world sun value.

 

I've only been in the industry for a year and half and I'm trying my best to learn as much possible and adopt the best workflow practices. Still a long way to go but I'm getting there!

[Dave Buckley]

Yes sticking to real world values isn't a bad idea at all, but you'll probably find not that many people use the vray sun anyway. Most people tend to be HDRI people these days, and even then they start doing all sorts of funky stuff with the gamma of the hdri, and that depends on which hdri you use, some i find need to have outputs of 1, some need outputs of 80, it just varies so wildly. Providing scene units are correct, and the model is the right sisze, you'll soon find what light settings are correct. FWIW when I do use the vray sun I tend to leave it on 1 however the other day, the client wanted more sunlight, so I just turned it up. Had I changed my exposure it would have affected all my other lights, and they were all fine. You could ask on here what workflow people use and the first ten would probably all be different.

[aaronrumple]

What's your camera settings?

Vray camera with exposure set at 1/100th second. ISO 100 and F8 to F11 have always worked well for me as a daylight model using Vray sun at the default exposure of 1. Typically, I'm using a reasonably low sun angle for either early morning or late afternoon. I always test with a material override of RGB128-128-128 on the building and a something a little darker for the ground plane (RGB64-64-64) I find that compensates well for parking lots and other dark planting material.

[Corey Beaulieu]

I think that there is much more to understand about what is at play...

 

In a Max scene anything is anything. It is why we cling to "real world" values. I have tried many times over the years to work with a reduced Sun multiplier, but have ultimately landed on leaving it at 1.0 barring an extreme scenario.

 

When you are lighting your scene, you have to make a decision about your exposure. You have to choose to expose to the Environment or to the artificial lighting. Once decided you should use a Neutral white balance and start to place lights throughout the scene or simply place your sun and sky. Using only the artificial lights or only the Sun/Sky you should then set your exposure.

 

For this I use a white override where the white color is 165,165,165 and continuously sample the render from the frame buffer until the brightness nears those values (sample the areas where this only direct light as light is additive.) If there is one channel or another that is significantly higher then I may proceed to white balance the image, but you can also take an average value from your sample and consider that your brightness.

 

Once you have established your exposure, then you can either turn on your Sun/Sky (assuming you were exposure to the artificial lights (Interiors mostly)) or you can then proceed to setting your artificial lights about the scene.

 

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The Sun has many other parameters than simply the multiplier that can come into play here. If you drop the turbidity to 2.0 you will get less horizon fog and the ozone (0.0-1.0) controls the coloration of the sun. 0.0 is more warm I believe and then 1.0 is more cool, though I could have that exactly backwards.

 

You can also use the Sky Model to help you out in controlling the sun. I find Clear to be the brightest and Overcast to be the softest. Preentham et al is a decent standard, but you may want to experiment. And the size multiplier will help you sharpen or soften your shadows.

 

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Even if you are going to be using an HDRI for our lighting, you should begin with a Vray Sun/Sky. I would suggest using a Daylight system to setup a Sun/Sky scenario similar to the HDRI you are going to be using in order to create a camera exposure that is within the bounds of reality. Once you have that the values used in the HDRI map won't matter, you will know your camera is largely correct and then you can continue to use more realistic values for your artificial lights.

 

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A Linear workflow has always been my go to for exterior imagery, but I find that Reinhardt works best on interiors. The best understanding for these two options comes from a Blender forum, but LWF seems to act most similar to a camera and Reinhardt works most similar to our eyes. This means that by introducing a lower burn value you are going to curve down your bright values for the sake of saturation and result in a slightly darker image, as well as more saturated and less burnt one. This can allow you to brighten your exposure and ultimately soften your shadows, which can be desirable, but is ultimately not a true LWF. This does not, however, effect your ability to composite in 32-bit and "add" all of the passes accordingly. It merely means that a small curves has been applied before saving your elements to create this lower brightness, more saturated image.

 

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In the end you are left with a lot of choices to make. But these are choices that every real world photographer are making and this is, in my opinion, what is going to set one artist aside from the other. The way that we all work when it comes to the marketing image is that the design is complete and the known is known (ideally). We are no longer left with guess work for where lights go and what lighting scenarios are accurate. We need to start thinking and acting like photographers and setting cameras up for hyper-accurate conditions and then adding maybe a few bounce cards here or there to get softer shadows or a couple of post production tricks as would any photographer, but the beauty of a physically accurate image comes from the delicate balance of the very real lighting conditions at play.

 

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To post script this long message (I'm sorry), I would copy this from the Vray Help menu:

 

By default, the VRaySun and VRaySky are very bright. In the real world, the average solar irradiance is about 1000 W/m^2 (see the references below). Since the image output in V-Ray is in W/m^2/sr, you will typically find that the average RGB values produces by the sun and the sky are about 200.0-300.0 units. This is quite correct from a physical point of view, but is not enough for a nice image. You can either use Color mapping to bring these values to a smaller range (which is the preferred way) or you can use the Sun intensity multiplier to make the sun and sky less bright. Using the VRayPhysicalCamera with suitable values also produces a correct result without changing the sun and sky parameters.

 

It seems like they may be suggesting that the Sun/Sky is overly bright, but I believe what they are saying is that you should either Color Map it by reducing the Burn value or at the very least you can reduce while keeping in mind that the 1.0 should work and a lower value is more in the range of 0.8 than 0.01. You may as well turn it off at that point.

Edited August 10, 2015 by CoreyMBeaulieu
added where to sample light

[martinhoura]

your approach is way to difficult - do you still end up with an image after all this or just a bunch of pixels with correct values?

[Chris MacDonald]

your approach is way to difficult - do you still end up with an image after all this or just a bunch of pixels with correct values?

 

Just because there is a lot of text doesn't mean it's difficult. What exactly are you struggling with?

 

I more/less do the same as Corey. I know how a camera works in real life, so I simply apply this knowledge to the renderer and it always works as you'd expect it to.

 

Out in the real world, if I take a photo that is overexposed do I turn down the sun? No, I simply adjust the camera settings until the exposure is correct. It's really, really simple.

[martinhoura]

yes, but that's not exactly what Corey said, is it? even with real life cameras you can do push/pull/cross processing - I mean fair enough, that has only limited application in regards to digital cameras but even that shows that with such a simple technique you could take your final work very very far. I am just tired of the fanaticism in the cgi world, what is right/wrong workflow and what sort of standards we all should be using - I agree as to that you should set your exposure to be somewhat correct but constantly sampling your pixels to be exactly 165,165,165 is a pure OCD. As Dave said we are not limited by any of the real life constraints (although we can benefit from them) so why is everyone suddenly taking this scientific approach to imagery? I even struggle with LWF to be honest - the only real life scenario I can think of where it makes sense is when you need to have all your input/output consistent across a few departments - but if not then why not take it further and see what happens? we have all this options and possibilities available at our disposal to use, misuse and even exploit but barely anyone seems to be doing that. photographers are using correct exposure and a few bounce cards because they have to, we can and should be doing whatever we want. if I feel like I need 25 spot lights to light one chair in the middle of the living room, I will.

 

tl;dr experiment goddamnit

[Chris MacDonald]

The whole point of LWF is that you will rarely need 25 spots to light one chair; your light goes a lot further with LWF. I honestly don't know how/why people struggle with it?

[Corey Beaulieu]

Martin.... settle down.

 

The process I outlined was more explanation of Vray parameters as there are different artistic choices to make. The times when I got more specific to my own process (If you felt like I was saying that you MUST do it my way, then you misread) such as the sampling of the 165, the point I was attempting make and apparently missed, was that you can consider camera properly exposed when you can sample the color of your material and they match. I chose 165 because that is the color white I use.

 

Above all.... camera exposure should not be a game of roulette. Lighting needs a scale and how you capture it is your best controller. If you are off in your light settings because your camera is setup wrong then you start to become off in your materials and your render setting can get haywire. LWF is dependent on your lighting being rational so that the colors of your materials stay rational.

 

You may see this as technical and to some degree it is, but to make such a case for incorrect exposure is silliness. Experiment on conceptual stuff. Experiment with DOF and with designs. Tryout different lighting scenarios and have fun with color, but don't call someone a fanatic because they suggest you set a solid groundwork for your image.

 

To get a good exposure might take 15-20 minutes if you have a goal in mind. How long does guessing take? are you factoring in all of the time you spend fixing it in post when you think of your response?

 

and here is the best explanation of LWF that I have read if it helps:

 

http://renderman.pixar.com/view/LinearWorkflow

[Francisco Penaloza]

To answer the original question, if your image look to bright with default V Ray sun is because you are not using the right exposure or because your colors are too bright. as Corey explained early, white in LWF is not 255. You can try 200 or 180 or less and you'll see a big difference, the same with your Bitmaps.

As rule of thumb for be for a typical "day" render ISO 100, F-16 Shutter 90 or 100 should give you decent exposure. Actually the default from V Ray, ISO 100 F-8 and shutter 200 should works fine too. in reality everything V Ray default should work fine. from there each artist should put his/her style on it. I know is not your case but new users of V Ray start to clicking buttons left and right and then they complain that the software is wrong. If with default values you don't get it right, there is something strange in your setup.

 

 

Regarding, Physically correct HDRI. I am not sure of that. there is so many sources on the internet and some of them are really bad, you should not take them as a bench mark. even some IES values are not 100% correct. I can't remember where I read that there is some discrepancy of how they write the IES data, some 3D software read it wrong. Having said all this, trying to follow one workflow it is OK as a starting point or rule of thumb. But it is not a sin if you have to adjust here and there to make the image "look" good. We are in a fake environment already, making fake places to look fakelly good, so saying I work physically correct, it does not make seance IMO, if so you should be doing lighting studies and not renderings right

[Chris MacDonald]

Quite right, regarding HDRI. It depends where the white point/exposure is set within the file - which can be anything on a floating point file.

 

The only "real world" benchmark we all have in our lives on a daily basis is a lightbulb. Use a 100w bulb (circa 1800 lumens) as a point of reference if you need to.

[Nic H]

post some images imo.

 

arch vis is so unnecessarily preoccupied with numbers and maths, as an industry its certainly 'on the spectrum'

that's why there aren't many good images, dudes are just checking their pixel values

 

(that said your sun should work fine at 1.0 with 'standard LWF')

[Chris MacDonald]

I don't get too hung up on it provided I can use "real world" camera values. Whatever the HDRI multiplier ends up being is entirely irrelevant as long as the exposure is correct on the camera.

[thomascoote]

I've taken the advice offered up in the replies of not being so stringent when it comes to sticking to certain values and workflows - for example I ditched LWF and went back to my old Reinhard setup, and my interiors are looking much better already.

 

However, I'm still having the issue with the sun and sky being ridiculously bright at values greater than around 0.001. Very strange, anything over 0.003 becomes absolutely nuclear, even with clamp at 0.9. Strange. However, it's looking right now, so that's all that matters I guess.

 

Oh, and I'm pretty sure my exposure is set right for interior scenes. I'm lighting my scene with strip lighting at around 1400 lm, with exposure settings of roughly:

 

F: 4

S:25

ISO:100

 

This is the result - by no means perfect but it's all that's required for the client. This is with the sun and sky set to 0.003. Anything higher it bleaches the scene. I took the advice earlier in the thread of turning off the sun and sky, and setting the exposure to the interior lighting before playing with anything else, so I'm pretty sure my exposure values are all fine?

 

[thomascoote]

Render Settings

 

 

It also strikes me as quite odd that to get any sort of anti-aliasing I'm having reduce my colour threshold to absurdly low values aswell.... (Sample rate pass is entirely blue above 0.003)

 

I'm starting to think that this may be an issue with the scene? All software I'm using is 100% legit by the way, so no dodgy "cracks" or anything. Anyone seen anything similar before? Or am I missing something extremely obvious I'm going to slap myself about when I see it?

Edited August 11, 2015 by thomascoote

[Corey Beaulieu]

Would you want to share your file?

 

It seems that something is off and there are just too many questions to ask.

 

Image does look good though, so in a sense, who cares, but 0.003 is basically off.

[thomascoote]

Would you want to share your file?

 

It seems that something is off and there are just too many questions to ask.

 

Image does look good though, so in a sense, who cares, but 0.003 is basically off.

 

Sure I don't mind sharing it. It will have to be tomorrow though, I'm mid way through an all nighter to get this in for the morning so a little busy right now

[Corey Beaulieu]

Sounds good. Just post it however, when ever. If you want to PM me and email, etc....

[simonm]

hey Thomas - how did you go with this? Im always experiencing this problem too.