Exposure discrepency in VRay Camera

[vlado]

if it is so, why is dynedeans images so different to yours ? is it scale related?

Like I said, it's all in the materials... Notice the extreme color bleeding in Dynedain's images, and its lack in the photos. This is not because V-Ray calculates color bleeding wrong or because there is something wrong with the physical camera, but because the actual materials in the real life are much less reflective (e.g. darker).

Best regards,
Vlado

[vance3d]

LWF would seem to be the key in this case and creating materials based on that.

V Miller

[Dynedain]

It does seem that LWF is important.

When I duplicated Vlado's LWF and color mapping settings, I was still getting a horrendously burned out image for the sunset settings.

Of course, my materials looked very washed out in the editor when using those settings (I had picked things in the middle of the spectrum, trying to stay close to neutral gray at 128,128,12.

Vlado's materials were set much much darker. They look almost black in the default Max color/lut settings, but fine when working with LWF.


Vlado's darker materials in a non-LWF scene render extremely saturated, and still a bit blown-out. So simply darker materials isn't sufficient.

Completely switching my scene to LWF (which I've been reluctant to do since we haven't gotten a color calibration device yet, and how it affects our non-3dsmax workflow...) with Vlado's darker materials got me to results similar to Vlado's. I think my rendering is still a bit too bright because there aren't enough objects in the scene to absorb the light, but it's much more in range of acceptable results than what I was seeing before.

[inf3rno]

Sorry, but i don't know LWF.... What is it exactly, related links prehaps ? Thanks

[aphex79]

http://www.chaosgroup.com/forum/phpB...ic.php?t=15303

[inf3rno]

Thankls aphex79

[inf3rno]

ok, i use a color correction software/hardware to setup my CRT monitors (Pantone Spyder2 ).
So it's fine but i have a prob with Sun/sky system. The sky seems dark and my sun very bright. i use default sun settings with a vray sky in vray envirronment map and reflection.

Is there a way to define exactly the position of sun for a specified location on earth (like maxwell do by define longitude/latitude/Day/hour). It would be so great if we can have this with vray.

[inf3rno]

ok i downloaded vlado scene and find my answer...

[studioDIM]

if it is so, why is dynedeans images so different to yours ? is it scale related?

Like I said, it's all in the materials... Notice the extreme color bleeding in Dynedain's images, and its lack in the photos. This is not because V-Ray calculates color bleeding wrong or because there is something wrong with the physical camera, but because the actual materials in the real life are much less reflective (e.g. darker).

Best regards,
Vlado

I can confirm this from plenty of actual experience.
Especially when working around phisicality, i tend to work with VERY DARK materials compared to standard renders.
It allows for a faster light decay, making long tracing somewhat faster, and a much nicer output generally.
How much darker depends, but my whites are generally at most 120 grey, my blacks and very dark greys go from 1 to 12 grey in the diffuse, and something within the reciprocity law for the speculars.
Then and only then i can start exposing.
No point in asking vray to mimick reality when the materials in the first place do not

Lele

[samuel_bubat]

hmm.. a stupid question.
If a photographer would have the opportunity to adjust his exposure
with gain, gamma, brightness, levels with just some interactive slider.
(wich is of course not possible because some dark scenes require
such long exposure times that you wouldn´t be able to do it interactive).
Do you think he would still mess around with with fstops.. etc ?
I guess not. And we 3D people who have exactly that ability with max log. exposure control (just one example) find it innovative to make our lives
hard by using a system that is not interactive, requires test renderings
and adjustments with parameters that were created for real world environments where such kind of handling is the only solution ?
Somehow I don´t get it. I mean if you need to match a rendering on photo. With interactive exposure it´s a thing of maybe one minute to integrate (exposure/colors).
So why should someone mess around with fstops when you have an interactive exposure control ? Also Cameras have very unique
color/intensity curves. So you´ll have to correct the image anyway.
This is nothing but a toy.. for scientists in my eyes (just like Maxwell).
I don´t remember one customer in the last five years who asked me for a "physically correct rendering".. what they want is a good looking
realistic image.And That can be a huge difference.
If I get photographs from customers that need to be integrated,
usually that guy has no clue anyway what settings he used and most of the times I need to correct the photo before i integrate it.

Absolutely no offence against Chaosgroup at this point.
1.5 is just phantastic. They did a great job.
With this feature they were just doing what the masses are screaming for. Especially after this rediculous Maxwell Hype.
So please tell me. In wich (non-scientific) case is this kind of
exposure control superior compared to other interactive solutions we allready have ?

cheers,

[vlado]

There are reasons why exposure should be done in the rendering, and not as a post-process:

(*) Since V-Ray is an adaptive engine, it needs to know how a certain part of the image will look for the observer, so that it can make its guesses of where to spend more efforts. The more it knows about this, the better it can guess. E.g. there is no point of spending horrible amounts of samples on burnt-out areas, when they are going to remain burnt-out regardless.

(*) Antialising is another reason. If you have your linear output with intention to adjust brightness (exposure) in post, you are likely to run into issues with antialiasing of bright objects. The renderer can do better antialiasing, but only if you give up the idea of adjusting the brightness in post too much (since the HDR information must be clamped).

In contrast with other renderers, in V-Ray the color mapping/exposure actually affects the rendering process to make it more efficient. Of course, minor modifications to the image are always required as a post-process and this can't be avoided, but in general it is a good idea to get as much of the desired result into the rendered image as possible.

On another note, I've always thought that Color mapping alone is enough for this purpose, but since people wanted all the f-stops etc... there you go.

Best regards,
Vlado

[Dynedain]

On another note, I've always thought that Color mapping alone is enough for this purpose, but since people wanted all the f-stops etc... there you go.

Physical Camera settings has a big advantage over Color Mapping. Either way, you need to spend time fiddling with it to get the right settings for the render, but with Physical Camera, at least you can get into the right ballpark faster when trying to match to a real photo.

[themaxxer]

well, I am very happy about the physical camera system. I know the functions of taking photos better than the 'interactiv' and theoratical way of any rendering system.

thanks to vlado and his team.

best regards
themaxxer

[Gijs]

@samuel_bubat: beside all what has been said, it has the potential advantage to exactly mimic a real life setup for testing materials. Again look at the earlier results of Dynedain, where he had used too bright materials.

[inf3rno]

Vlado, what for you a good real white material ? A 120 Grey like said StudioDIM ? I don't understand why we need to use so dark material, it's very hard to define good color in dark...