VRay Sun, Sky and Physical Camera video tut + Bonus Script!

[aaron-cds]

LELE,
I just wanted to thank you for the tutorials. I'm going to watch them one more time before I start asking questions.

I'm a moderator at www.vizdepot.com. I posted an announcement to let people know about this great thread.

Micha, please start your own thread to present your OWN theories. That would be more helpful.

[Micha]

Sorry, I thought we could discuss the tutorials and I see problems with the 0.255 method. But I'm the only one and stop to discuss this subject. If anybody is happy and get nice images, than it is fine.

[studioDIM]

Sorry, I thought we could discuss the tutorials and I see problems with the 0.255 method. But I'm the only one and stop to discuss this subject. If anybody is happy and get nice images, than it is fine.

I had this tutorial reviewed and approved, before releasing it.
I wouldn't DARE release an hour's worth of deductions without first asking for general correctness to those who made the tools in the first place.
The method was deemed correct at large by someone who knows vray better than me and you (hint ).
Second hint may be that either me and the lot of users around here are a bunch of blind fans or perhaps there is some ground in the things i expose, and in the cross-examination of a few dozens professional vray users.
Please, let's get back on track.

Lele

[Micha]

Lele, if you like, could you explain why and how the 0.255 method work? If not, we can stop the dicuss too. I don't want to be the bad guy. Only I try to bring together the ideas of your tutorial and my experience/tests. I don't understand:
(a) Why it is no problem, that indirect light get a strong attenuation (see my 50% vs. 2% example)? Or does GI work other? Is the default GI bounce of Vray to strong?
(b) Why is it necessary to change the relation between diffuse reflection and sky intensity? Maybe there is a bug in the Vray engine and your method help to work around. Is the sky as reflection environment to dark? If yes, which output gamma is used?
(c) What do you think about my interior test? Do you think the 0.255 image is ok, is better than my previous workflow image? Which result do you prefer? Or is your method not recommended for scenes with many GI bounces? Or does RC3 handel GI bounces other than my current lower Vray version?
(d) And I'm not a big friend of special workflows, I remember me on an user how says to me: the usage of AIR (my previous render engine and I suggest many tricks and workflows) is like a preview for Alzheimer. Now she use Maxwell. What she says is not so wrong or? Sometimes I run in render problems and I know, in the past I found a solution, but I can not remember me.
(e) Do I complete missunderstood the 0.255 method? Do you recommend to set each color and texture at 25% and to use an exposure correction?

And a new question:
(f) is the 0.25 method useful for HDRI environments too or do it stick on the physical sky?
I made some tests with an env map: I have no problem with a dark sky, so only I set white at 200 (~80% white) -> image looks a little bit flat. Next test: secondary GI at 0.5 -> images looks more contrastful, I like it more than the previous. So, 0.5*80%=40%. It's not so far from your 25%. So, my conclusion for me: lowering the GI bounce intensity is a way to get more contrast. If additional the sky is to dark, than it helps to use the 0.25method. But be careful at interiors.

I'm very interested to understand your method. But if you say, belive it or let it be, so is it ok and I stop here.

[studioDIM]

Micha, i show this in the tutorial, and can't honestly understand what's difficult about it.
The sun has an intensity of 385 float.
That is, in VfR set a vray light to white with a multiplier of 385 and no decay.
See what you can do with the vray materials alone to try and compensate for it.
The answer is "nothing".
That's what you seem to be missing on the whole issue.
I said it many times now, 0.255 is not scientifical a number. feel free to use what works for you.
The point is that with such strong intensities for lights there have to be a few steps to be taken to work comfortably and predictably.
I am only proposing to work with the physcam and the materials together.
It makes NO sense to use this method other than with sun and sky and physical camera.
See if you can put your hands on a max9 demo, and on the public beta of 1.5rc2, and try for yourself.
When in doubt, read the previous posts, don't keep asking over and over the same things, i'd REALLY like to move on from here to new, and better things.

Lele

[teabag]

Amazing tuts studioDIM....very useful i will try this once at a new exterior project

[studioDIM]

http://www.scriptspot.com/lele/VRay_...erter_v1.1b.ms

should now work with pretty much any type of map.
Note it will put any map type without an embedded "Output" pane within an "output" map.
Memory consumption may rise considerably for large scenes (while not being the script's inherent fault, i thought i'd warn you on this one...)

It also works in relative and absolute mode.
Ie. it will multiply by the selected value, or set the output to the selected value itself.
Nice to use it in relative mode with a mutliplier of 1.1 / 0.9 to change slowly the contrast of the rendered image (brightening materials and lowering exposure loses contrast, the opposite gains some)

Let me know if you encounter any more issues.

Lele

[aaron-cds]

Thanks for the update. Any word on when you'll have the interior tutorial ready?

[studioDIM]

I don't think anytime soon...
Am pretty busy at the moment, and will need to find some large-ish amount of consecutive time to prepare it.
We'll see what i'll be able to squeeze in...

Lele

[flipside]

Hi,

Interesting workflow

A few questions:
Why do you leave the max gamma correction for color swatches turned off? Wouldn't that maybe solve the problem of the big difference between material slot preview and rendered color (for example with the brown-yellowish color)?

Once you decided on using 0.255, do you keep that number for all your material colors in that scene, and simply work with the color selector?

Do you also apply the 0.255 multiplier to reflection, refraction and whatever other color swatches?

Thanks,

wouter

[flipside]

Does anyone have an interior image rendered with exactly this technique?

I tried it first with an exterior, as in the tutorial, which works very well. But with an interior, I'm facing the old problem again of light not traveling far enough into the interior (like when not using gamma correction in the old days).

Even with interiors with large windows, you get very high contrast in lighting, probably because light has lost all of its energy already after a few bounces.

[studioDIM]

Why do you leave the max gamma correction for color swatches turned off? Wouldn't that maybe solve the problem of the big difference between material slot preview and rendered color (for example with the brown-yellowish color)?

Maybe it would, but when i colorpick i personally refer a lot to numbers, rather than hues. I'd like those to behave linearly, with a gamma applied they wouldn't anymore.
[quote]
Once you decided on using 0.255, do you keep that number for all your material colors in that scene, and simply work with the color selector?
[/unquote]
Well, yes and no.
Yes i do suggest to prepare a scene with an ideal number for (de) multiplier, but that 0.255 is as such because of two reasons: A) it's similar to 255, so it's a number we all know and remember well; B) it does work fairly well with the camera and sun and sky in outdoors.
And No because i suggest to make use of the script i prepared to change the material/maps multipliers and see what changes counter-balancing with the camera.
You'll notice that brighter colours (> 0.255 multiplier) will wash the image out a bit, while darker ones will contrast it more, if we always keep a bright pixel at the same float intensity through camera exposure.

Do you also apply the 0.255 multiplier to reflection, refraction and whatever other color swatches?

Again, yes and no.
Yes i normally dim reflections a lot (if diffuse was one fourth of the old value, this can be the same, or slightly higher if it needs to be a dominant reflection) , but do not change bump, for instance. That's an "unshaded" channels, in that it only depends from light /camera incidence, not so much the intensity of it.
Refraction doesn't actually need to be dimmed, but we can finally make use of fog properly, with reasonable multipliers, as the passing through light is so strong, the fog will behave in what i personally think a more consistent way compared to old lighting methods.

Hope i answered properly, if not, fire away!

Lele

[studioDIM]

Does anyone have an interior image rendered with exactly this technique?

I tried it first with an exterior, as in the tutorial, which works very well. But with an interior, I'm facing the old problem again of light not traveling far enough into the interior (like when not using gamma correction in the old days).

Even with interiors with large windows, you get very high contrast in lighting, probably because light has lost all of its energy already after a few bounces.

I gamma corrected this twice, without realising it: 2.2 colormapping + srgb.
Bear in mind that when exposing for an interior shot, the outdoor seen through the openings will glow brightly.
With that in mind, exposing the camera will cure ALL the issues with the interior shot, overexposing the openings.
When in doubt, check the "kitchen.hdr" image. see what happens to the windows and doors when you get a decent enough interior exposure.

Lele

[flipside]

Yeah that looks like a proper answer

So my other post about the interior scene (probably posted while you were typing your answer), you will probably say I have to find the right multiplier value for that scene?

[flipside]

ok let's post simultaneously

will try some more on a decent scene, and I will also check your script.

thanks,

wouter