Sun and Detail Enhancement

[merlik585]

Re: Sun and Detail Enhancement

Thanks Damien,it is clearer,and I will give it another try

@Micha
Yes I already found that ''bug''

To tell you the truth,what I prefer since I have a long background in photography,is use the physical camera,and play with the f-stop(that brings my wisk back,please attach the dof with the physical camera via the f-stop,like a real camera.),the speed and the iso,changing the sun and sky intensity to me is not very fair,so far I have not touch the intensity in production.I have done it just to play with.

Renee

[dalomar_cg]

Re: Sun and Detail Enhancement

Renee

I think that using an HDR or another image in the background is fine. I'm not sure if I mentioned this in my previous posts, but I recommend that you set the proper camera exposure with the Sky setup. Once you have the proper exposure and multiplier for matierals (.255 if you like), then go back and set the HDR and increase its intensity until it is properly exposed. If you have HDRshop (or render in in vray real quick), then you can measure the intensity of the brightest part of the image, then divide 385 by the brightest part of the hdr and that should get you in the ballpark for the correct intensity.

I also would like dof back on the physical camera, but I'm not sure our timeframe on that. I don't blame you for not wanting to use this method in production right now. Its alot to switch over, and not all of the kinks are figured out with it yet. I do think that it will be a good method once all of the nooks and crannies are investigated.

[Micha_cg]

Re: Sun and Detail Enhancement

Phys Cam F-stop without DOF and shutter speed and ISO - this the same like standard cam and color mapping multiplier or?

I have a long photography background too and would like to get a full working phys cam too. At the moment I stick at the standard cam, because I like to use the DOF and the other features are not needed now.

Here a quick test: texture intensity (sky) at intensity 8, so that the sun is less intensiv (a day with much water in the air). First I render the scene with GI multiplier 0.25 and the brighter buckets are rendered with sec GI multiplier 0.6. I think, 0.6 give a better white material look and the sky is ok. So, I can choose what I want: more or less sun, more or less correct white material and indirect light bounces.
Interesting for me: the GI at 0.25 ala Lele method create dark grey object on a white ground. It looks like I used different materials, but anything is the same white (value 230). I think, the human brain feel how much light should be indirect reflected by white materials. A 25% indirect reflection is not typical for white colors.


I wonder me that I never have seen posts about problems with the sun intensity at the Maxwell side. I suppose so, Maxwell use a less ideal clear air model and the sun is less intensiv.

[Gijs]

Re: Sun and Detail Enhancement

I am bit late to pop into this thread. Yesterday evening, I was reading the Lele thread roughly and felt ashamed about the way you (Micha) was treated. Anyhow, I just wanted to mention that I don't see any reason to use a 0.25 multiplier for materials since this gives unrealistic attenuation. On the other hand I also don't see any clue to lower the GI multiplier(s). Of course this is from my own perspective, a perspective that is leaning towards making physically accurate renderings.

If physically accurate behavior is not an issue, then there is no point of discussion left, because it is all reduced to a matter of taste. In my opinion, since Vray uses physically accurate light calculation, we should only try to adjust materials and the right tone mapping to make correct renderings. If one decides to use a 0.25 multiplier for all materials it is similar to saying that there is no material that has a higher reflectance than 25%. We have all seen in the exact same thread from Wouters tests, that this leads to undesirable attenuation and reminds of the dark gamma 1 days.

I agree with you Micha that if this would be the only way to output visually pleasing renderings with Vray sun and Vray physical camera, it's time to write a bug report.

[Micha_cg]

Re: Sun and Detail Enhancement

Thanks.

Gijs, I wrote at the bug section post some minutes befor. Maybe you could share some thoughts about the sun&sky system. I'm not happy with the strong intensity of the sun and know only, that Maxwell dosn't show this effects. Maybe you have some ideas, what could be done. I'm curious to talk about the sun. Interesting for me is, that in the past, I have rendered Maxwell environments per mirror ball method (for lighting of Vray renderings) and the reflection of the Maxwell sky and sun show no high intensity, - no HDRI was needed. Maybe Maxwell is not physical correct and use a sun fake. ... but it works well.

[merlik585]

Re: Sun and Detail Enhancement

I spent the major part of the day yesterday,watching the videos again and again and doing test after test.
And my conclusion is the same as Gijs,and his opinion is exactly the same as mine.I don't see the point on using a .25 multiplier.I have much more realistic rendering leaving the sun,sky and materials intensity where they belongs,and play with physical camera settings.And that is what I want.So after all the test at least I have a clear mind on this,and I will stick to it.But as Gijs said it is matter of taste,and taste I have learn...is not open for discussion.

@ Micha

I don't think the sun is too bright,using the physical camera and right settings I get exactly what I want.

And as a good start point use the sunny f/16 rule

speed and iso at about 100

for an overcast day go with f/8 and paly with it


Renee

[Micha_cg]

Re: Sun and Detail Enhancement

Renee, I don't understand how the camera change the high clear air sun:shadow ratio to a lower sun:shadow ratio of a day with much dust and vapor.

But, yes, the sun light is not much to bright and if I like to catch high contrast, than I use an analog film curve at the framebuffer (something like manual exponetial with more control than the burn option).
At the moment my biggest problem is the high intensity of the reflected sun (like at the scene here tested)

... or here an other setup - sun artefacts

[dalomar_cg]

Re: Sun and Detail Enhancement

First off I agree with Gijs that this whole thing is about being as physically accurate as we can be, and that if that is not your goal, then this whole discussion is a non issue. That doesn't mean that physically acurrate images are any better or worse then ones that aren't, and ultimately it comes down to how comfortable the artist feels and the results they can get from the system they choose to use. I think as long as you're using the sun/sky at their correct intensities and a physical camera then things are well along their way to being physically correct. Some will see the materials as a next step, and some won't, again its at the hands of the artist.

I personally don't think that the sun is to bright for several reasons. First off if you try and stare at it, it will blind you, and we are how many hundreds of thousands of miles (or km) away. If it weren't that bright, then I think things would be a bit different than they are. Also, the sun/sky model is based on research, and I've read through the main paper that Vlado built the model on, and all seems inline from what I've seen.

Their are a typically a number of antialiasing artifacts that come from using the sun, and I definitely see this as an issue. It would be nice if there were a better way to calculate the antialiasing in those areas, to avoid these artifacts. I know that the aa is actually very accurate, but the rendered result is not very desirable. I'm not sure how effective Sub-pixel Mapping+Clamping Output is on dealing with these areas, but I don't want to clamp the output just to get a decent result.

Lastly, I agree that Micha was not treated very nicely in that thread. However, he was making comments about a method that he could not even test via vfr (we didn't have the sun/sky/cam at that time). I feel that because of this Lele felt that Micha was criticising the work that Lele had put into the tutorial, and that his observations could not truly evaluate the method with vfr.

And I end on with this last quick comment...to each his own ;D

[merlik585]

Re: Sun and Detail Enhancement

@ Damien

Bingo !

@ Micha

The camera won't change that,if I want more humidity in the air I play with turbidity and ozone and set the size of the sun to a huge number to get very very very soft shadows.

Renee

[Gijs]

Re: Sun and Detail Enhancement

here some tests of the sunny f/16 rule.

based on this I guess my materials are a tad to dark, but with some exposure correction (second image) all looks pretty well.

[merlik585]

Re: Sun and Detail Enhancement

This is also what I get.so I went and read this on spot 3d.
That is why now I go with f/11 or f/10
most of the time

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 other parameters.

I am reading this again,and I find a contradiction here(may be my english is not good enough)Damien could you please tell me if I understand correctly.

It says that the sun and sky have between 200 300 units for the light.It also says that it is correct from a physical point of view,but NOT ENOUGH for a nice image.If it is not enough why would it suggest lo lower the sun intensity to make it less bright,or use the proper camera settings...in my opinion it would be the other way around,if it is not enough,it should be brighter,than using a lower f/stop (bigger aperture)exactly what I have found in my rendering and as Gijs example above shows.



Renee

[Gijs]

Re: Sun and Detail Enhancement

not enough: this refers to the fact that although the intensity is physically correct, that alone will not give you a good rendering, you need the right colormapping and/or physical camera settings to get a good image.

[merlik585]

Re: Sun and Detail Enhancement

Ah thank you,I thought it means that there was not enough light with that equation.

Renee

[joe_b]

Re: Sun and Detail Enhancement

If you guys have any feelings on what the default settings should be / what parts should be automated I'd be interested to hear your suggestions. Perhaps a thread in the wish list forum could be started? That goes for VfR Sun/Sky implementation (mainly UI stuff), as well as the core V-Ray SDK Sun/Sky functionality.

[tangelder]

Re: Sun and Detail Enhancement

Hi people,

First of all. I am new to this all and studying hard. I dont know if what i am going to say will make any sence. So dont shoot me. But i wanted to pose the following question:

Does anybody know more about Albedo? I had a quick look at the following article:
http://www.jgsee.kmutt.ac.th/exell/Solar/Intensity.html
in this article the albedo is mentioned as follows:
"The reflection of solar radiation depends on the nature of the reflecting surface. The fraction of the solar irradiation that is reflected from the surface of the Earth is called the albedo of the surface."

In this article they writer gives a short list for the albedo of materials in real life.
vegetation: 0.2
pale soil: 0.3
dark soil:0.1
water:0.1
clouds:0.5-0.9.

Is this albedo value comparable to the multiplier of the rgb. If we take lele's remark in account for a multiplier of 0.255. Would this be comparable to a albedo of 0.25?
This is just a guess.... But if so, each material will have its specific albedo. So if we want to give the material the correct reflectance level of light, it would need its specific albedo. Please correct me if i am blattering nonsense...!

Cheers,

Joost