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

[siliconbauhaus]

cheers for the tute and info Lele.....go have some beer and enjoy chrimbo mate

[studioDIM]

Hey Micha!

The tutorial has no pretense to be "physically correct" (read the post above.)
We have no brdf/bsdf implemented in vray (yet? ), so mine is an empirical method to get the exterior shot in range ( i implicitly consider sun and sky at a value of 1 o be "correct" and expose the camera and materials to it).
I am not sure about the reflectance values you state (namely white being 80% reflective).
Reading here , for instance, seems to be closer to what the empirical method and the proposed workflow suggested:



These spheres have an albedo (in other words, "The proportion of incoming light reflected") of 0.1-0.3-0.1 in RGB for a "dark" green colour.
Under these circumstances, a much whiter material may be around 0.3-0.5 in all of them.
Of course, it's scaled down to 8bit, so there may be three ways to produce a white rendered pixel: brighten the material, brighten the lighting (like in the case of the picture above from the top to the bottom row), raise exposure.
Perception matters here, as we end up displaying on 8 bit devices.

As for gamma, LWF et al, i think a lot has been written, and i'd rather not get back into it ( i still smell smoke from past flames, lol).
I use gamma in my tutorial to brighten darker ares, as that's what a gamma curve does to pixels.
I could have saved an HDR image and have done that in post.
A sidekick of darkening materials is that you gain contrast, brighten them, and you lose it.

Hope i clarified bits, and i know i skimped on others.
We'll talk again about this after the holidays, anyways

Lele

[studioDIM]

cheers for the tute and info Lele.....go have some beer and enjoy chrimbo mate

Eheh, just had one wild nite yesterday.
It'll last me until at least new year
I'm getting definitely older by the day (duh!)

Lele

[_jaro]

I would love to see the video, but I'm having troubles to run it. I can hear the voice, but I am not able to see anything. What king of codes are you using?

[apexmotion]

Same problem here. Audio but no video.

[Olli96]

get vlc, plays everything
http://www.videolan.org/vlc/
btw, thanks for the videos studioDIM.

Olli

[studioDIM]

The one needed is the TechSmith codec, and you can find it @ http://download.techsmith.com/tscc/tscc.exe
Audio is in mp3.

I'm humbled hearing you liked the tutorial

Lele

[DaForce]

Still to this day im suprised just how many people dont know about that codec.

p.s. writing this on my 30" dell LCD hehehe

[studioDIM]

Still to this day im suprised just how many people dont know about that codec.

p.s. writing this on my 30" dell LCD hehehe

I'm SO glad you stopped calling it my '30" beast', mate...
Father Christmas is as well, his honour saved

Merry Chrimbo!

Lele

[themaxxer]

I read this post and for me the only problem is the VraySky. It seems to dark in comparsion with the whole image, when a VrayCam is used and everything else appears correct.

I have my own workaround.
I setup the scene and use the power of the VrayCam and its options. when everything is lit well, excepting the Sky, then I put an outputmap to the Sky. now the problem is the Sky. It puts some more light to the scene and the image has a blueish tint. to correct this I tint the "white balance" in the VrayCam rollout with a blue color out of the rendered image to compensate the blueish tint. and volià!

I am not a fan of correcting all the colors, when the only problem is the Sky. If I could make a wish, it would be nice to have an option to multiply the brightness of the sky but not its GI. I think the problem is the VraySky, it's "only" a map and it's also acting like that.

here is a rendered image.


...and here is the scene. you must have max8 and vray 1.5 rc3
http://www.pixelschmiede.ch/chaos/se...ht_vraysun.zip

I don't know if it's physical correct, but for me it's good enough.
I ask me how maxwell handles this?

best regards
themaxxer

[DaForce]

Still to this day im suprised just how many people dont know about that codec.

p.s. writing this on my 30" dell LCD hehehe

I'm SO glad you stopped calling it my '30" beast', mate...
Father Christmas is as well, his honour saved

Merry Chrimbo!

Lele

Yeah also my GF is not sure WHAT to think now

[studioDIM]

Hey maxxer, surely enough, it's one of the options i covered in the tut (darkening the sun multiplier darkens the sun as well; using an output map in the background slot does the trick too, even though i cover that when we have a white BG, rather than the sky), but we part from phisical-like behaviour from the materials, as well as bending what the Sky and Sun are supposed to do.
What i propose is to stop thinking in 8 bits: that is the heritage of old CG, not the new sun, sky and camera .
Maxwell is a closed system (it doesn't work with anything else than its own materials and cameras), hence it's a lot easier for them to automatically bring things into range.
Try the same render of yours as is, and with darkened colours plus gamma, and see what happens to rendertimes, and white dots

Lele

[ene.xis]

Try the same render of yours as is, and with darkened colours plus gamma, and see what happens to rendertimes, and white dots

Lele

yeah!
i double that! it seems a smarter way of exposing rather than mess up within the relations (physically correct) between the sun+sky+camera!

[helpdesk]

How is all this affected if I don't use the VRAY frame buffer and just use the MAX buffer? I modified my MAX gamma and lut settings to 2.2 with affect color and material editor set to on. I also have my bitmap input gamma set to 2.2. I am not getting the same kind of results Lele?

Best regards,
Dave Vaughn

[studioDIM]

In that case, using the colormapping settings will apply the 2.2 gamma twice.
You can leave the VRay colormapping gamma at 1 if you use the max VFB and the max gamma is set to 2.2 (or the other way around )

Regards,

Lele