Physical material

[Dark_Arkon]

It will be coll that in a next release there will be a physical material or something else to use with Physical sun and sky to avoid overbight problems.

I know that can be corrected with Lele's script, but it will be better for users in a native way.

Thanks.

[ene.xis]

what do u mean physical material?
isn it allready?

[Dark_Arkon]

If you use the Vray sun and sky. when you get a correct exposure for the sky, the shaders are overbrighted.

Lele has develloped a script to tweak the shaders to avoid the problem, but it's "just a tweak" and the shader appears dark in the material editor.

Not cool to tweak it.

So a correct native shader to use with physical sun and sky will be a good stuff.

[ene.xis]

u mean u want vray s diffuse chanel to be multiplied by a value?

[Dark_Arkon]

That is what the script make. but whem You multiply by .255

What you see in the material editor is a dark shader. Not really easy to use.

A material that appears normally in material editor, but have correct properties to avoid overbright with sun and sky will be helpfull.

[Dynedain]

Umm... you don't need physical materials.

If you are going to use the Physical VRay Sun + Sky and not change the multipliers away from the default settings, then you need to use the VRay Physical Camera so that everything is exposed properly.

The .255 method is a workaround in case you don't want to do camera exposure and don't want to touch the settings of the vray sun and sky.

The sun and sky are much much brighter than default lights. So to compensate you have to either:

• do exposure in the camera (vray physical camera)

• change the values on the sun and sky

• or change the values on all your materials to be extremely dark (the .255 approach)

[Codi]

As I understand:

1- If you expose the scene with the physical camera either you have a dark sky with "correct" materials or you have the sky properly lit but overbright materials.
50% grey material with diferent physical cam exposures:


2- If you change sun and sky values you dont have physical correct illumination.

3- The .255 method, wich is great but I agree with Dark_Arkon: is anoying having to work with such dark materials in material editor.
Same scene with grey multiplied by 0.255:


Altrough I'd prefer a global way to have correct material behaviour without having to change all materials in a scene ... wouldn't be possible to have a global diffuse and reflection multiplier? Would it be correct or this multiplier is dependant on the physical properties of the objects (metals, plastics, fabrics ...)?

Don't know if things have changed in version 1.5.00 with the new Sky values (I haven't tested it yet )

[^Lele^]

Let me clear this up a bit:
The script was named that way out of a (wrong, with hindsight) whim.
It was meant to tie in with the physical camera and sun and sky, hence the name.

The default vale of .255 demonstrably worked in versions up to and including RC4.
That will have to be changed for later versions (those with the new sky model) to something like .5, or even higher.

It's also quite demonstrable that the albedo of what is perceived as white under sunlight is WAY lower than what we used to set as 255 white in 8bit workflows, with lights shining at 255 white (1 float).
That was a hack, and a big one at that, due to the integer, limited elbow room the 8bits allowed.

What you see in the material editor -by default- is just that: your material lit under a 255 white light.
You can, and are most welcome to, multiply the light intensities of the mat editor by the reciprocal of the diffuse multiplier: 2 if the multiplier is .5, 4 if it's .255
You'll find the options under the mat editor options panel.
I didn't include it in the script as i didn't want to mess the material editor for everyone (and also because the multipliers may vary from material to material).
You will notice, however, that a 128 gray material with a 2.0 multiplied light will just look white, if more rapidly decaying.
Which is also what happens when you use the method outlined in the tutorial to which the script belongs to: a raise in contrast, due to a faster light decay.

Let me know if i ought to be more clear on something, and sorry for the confusion.

EDIT: it seems VRay doesn't take into account the light multiplier changes in the mat editor options. a bug, or a feature? Vlado?

[Neilg]

If you dont want to get lost in lele's post: You are overthinking things.
Do more test renders. Colour correct your textures more.

I dont see what the need for everything to be 'correct' is, we are all in an industry where we are supposed to make things look good. Sometimes, thats not realistic.

[Codi]

Lele, thanks for help me learn how light works in VRay with your informative posts

But still the .255 method looks a temporary solution to me, and I think some VRay native control, be it global or material specific, would be more useful.

Vlado already done what most people asked in the development poll, maybe there is something in the works for the second most wanted feature?

[mosetti]

Yes, physical materials or spectral shaders or anything close are a very important thing at this point, any news from chaos about it?