iray specular transmission can not work with back gorund color(image) .

kitakoredaz

I made new light shader by MDL  with specular  transimission.

(that means the emission obj   perfectly transmit the surface color , then the emission obj is not visible  in camera angle , and cast no shadow, but can emit light. )

it work without problem , when I use Render settings>enviroment>dome with HDRI image,, or Sun sky,.  and it can work when I set backgorund "none" too.

(then the emission light obj not rendered , no cast shadow even though I locate the emission obj in camera angle. )

but when I set "bakcgorund" color or image, then I use the emission shader with obj, the emission obj cast black (color 0.0)  shadow.  and ignore the backgorund color.

is it problem of Nvidia iray? or daz studio backgorund?

 

pic1 the yellow line square = emission obj,  with specular transmission  white,  no backgorund color.

pic2 render  image of Pic1 . , the emssion obj cast no shadow. then the outer area of scene items, keep transparent.

pic3   I set backgorund color as grey, then the corner of emission obj cast black colro shadow. (it seems transparent, but not show the backgorund  grey color)

pic4 render image of Pic3,  now the black shadow are (or transmitted area) is visible as black, and not fit with back ground color.

test and render  with newest  beta ds  4.9.0.36

Tobor

kitakoredaz said:

I made new light shader by MDL  with specular  transimission.

(that means the emission obj   perfectly transmit the surface color , then the emission obj is not visible  in camera angle , and cast no shadow, but can emit light. )

You can do this already just with the Iray Uber shader. You don't need a custom MDL, and unless you've integrated terms not used in Uber, it doesn't buy you much.

1. Apply the Emissive shader.

2. Set the color temperature to 0. This allows the color of the light to be controlled only by its Emission Color.

3. Do one or more of the following, depending on the shadow effects you want (or don't want): Set Refraction Weight and Index to 1.0; set Cutout Opacity to 0.0001.

 

 

kitakoredaz

Hi Tobor, at first I said you thank you much, because I learn many from your topic.

But about this topic, it is not problem about how to use Iray Uber shader, and how cut-out opacity work, and How I can achieve you already mentioned

in another topics, (to hide emission obj ).

It is about reflect transmission shader, which  need to work  as expected .  then at least about daz backgorund , it not work. it is not correct.

then I ask here. it is problem of daz background color , or it is problem about iray-shader.

at least,  reflect transimission bsdf need to work as transparent in iray, it should be designed not  cast any shadow, with backgorund color too. (I know I can use cut-out opacity too, but it is no reference about this topic)

Iray is PBR, I believe so, then the reflect transmission means perfect transmission.

I believe, even though I do not emit obj, the reflect transmission may not work with DAZ back gorund color.

then it is problem, or we can not use it as it should be.  I may wait daz correct their back gorund, or nvidia correct

the reflect transmission.

kitakoredaz

 I use diffuse_edf for emission,  and use  simple_glossy_bsdf for scattering surface,

 about this pic. with  , no glossy (roughness u and V - 0.0), with scatter_transmit mode.

Then,  I set the simple_glossy bsdf ,  tint : 1.00 (white) ,  that means all light color  should be transmitted and can not cast shadow.

Then I think, it may happen when I use specular_bsdf shader in MDL..

 

 

 

 

kitakoredaz

Ok now I seems it is problem about DAZ backdrop backgorund with iray.

I make  simple specular (transmission) shader by shader mixer, then check with iray dome (HDRI back ground), and DAZ back drop.

then just use camera head ramp, then check  it with intaractive mode. (may not need render any more)

pic 1 = with iray default Dome  , pic2 = with DAZ back drop (back ground color , I tested with back ground image too)

 

Tobor

The problem is if you don't share the full MDL and/or shader DUF, there's no telling if it's a problem with your shader or with Iray. Using the Iray Uber shader allows other people to try it in both 4.8 and 4.9. Otherwise people have to guess.

As I pointed out, you can make a shadowless and transparent (invisible) emissive object using the standard Iray Uber Emissive shader. In your tests does that also not work? You didn't mention.

kitakoredaz

>The problem is if you don't share the full MDL and/or shader DUF, there's no telling if it's a problem with your shader or with Iray.

So now you get my pic.  with shader mixer nodes.  but  when I said "specular  transmission" in title, I believe, 

we can easy test it in DAZ offer iray uber shader too.

 

"specular transmission" is not "cut-out opacity".  even though same effect we get with case.

It is actually simple problem.  in daz studio, iray transmission can work with bg color or not..

 

>As I pointed out, you can make a shadowless and transparent (invisible) emissive object using the standard Iray Uber Emissive shader.

 

 I know cut out opacity,  should work.  because I had used many times emissive object (without sutom MDL code, or shacer mixer MDL blicks)

 with set cut out opacity. with 0.000001 etc.  but when I ask about specular transmission, why I need to talk about "cut out opacity"?

it simply change my topic meaning.

 

 I made the shader, to easy use emissive,  specular reflect, (mirroer)  glossy reflect, and transmission shader with

 clear user parameter.   not made for emissive use only.   .

 

 "shadowless and transparent (invisible) emissive object" is not  problem. Actually I could it by cut-out  opacity, and

specular  transmission too. But  if transmission can not work with BG,  all transmission effect will  cause same problem, with back ground color.

we do not  use iray transmission ,for hide emitted object only.   if specular, glossy ,diffuse, transmission can not work with DS enviroment BG, I prefer to

not use Back drop with iray anymore.

kitakoredaz

In DAZ iray uber shader, to see glossy or specular transmission, Need to set transmission= refraction parameters.

(it just daz set  name so I think. not same iray MDL manner)

And cut out opacity can never show us color transmission with Reflaction index and glossy transmission.

if you apply material about  sun-glass,  you may not use Cut out opacity. if you apply shader for room wiindow,

you may not use Cut out opacity. then these transmission or reflact can not work with Back ground image.

 

that means we can not use enviromentpane > back drop, with PBR transmission for iray.

kitakoredaz

 I asked about it, in MDL forum before,, then got reply new iray version would  remove this problem.

But  In ds 4.9 1.25  bg color or map,, still seems not transmitted (reflact) color , without we set " thin wall" ?

it is still Iray Nvidia problem, or DAZ need a kind of bug report? (or future request?)