Thin plastic chair - Ghost = How?

[cecofuli]

Hi,

as in the title, I'm finding difficult, near to impossible, to obtain the standard shader for a Starck - Ghost chair.
Especially contrast between the dark edge and the internal color.
In attachment the 3ds max model and the photo reference. Do you have some suggestion?

[Ondra]

I would try refraction + attenuation color ;)

[maru]

Just a quickie. I bet it could also be faked by AO or falloff map.

What comes to my mind in this situation is that a "bias" parameter for absorption would be nice so that you could change "thickness" of the dark areas. Then it would basically work like fog.

[cecofuli]

Thanks. This is my test ( I need it for exterior project)
Yes, bias, like in VRay, will be very useful!

But.. why is my shadows solid and not transparent?
The light comes from a daylight system with CoronaSun.

[Ondra]

You would have to switch to bidir here to get correct caustics from using solid glass

[cecofuli]

Mmm... I have strange result...  :/
Just change Progressive to Bidir/VCM
BTW, why can I have a transparent shadows with BF/IM and/or LC, and here we have to change Renderer?
Or do you have to solve this problem (transparent shadow)

[cecofuli]

And... how can be possible render glasses (Onesided) of water or tables in glass with this problem and without these unrealistic, solid shadows? 

Polymax: I see in your render a table in glass. Why don't you have a solid shadow near the objects in glass?
http://forum.corona-renderer.com/index.php/topic,745.0.html

Also in this famous render:

[Polymax]

And... how can be possible render glasses (Onesided) of water or tables in glass with this problem and without these unrealistic, solid shadows? 

Polymax: I see in your render a table in glass. Why don't you have a solid shadow near the objects in glass?

Because light with soft shadows(sky light, big size emitters or coronaLights  make a great caustic in PT+HD or PT+PT mode.

fast test yours chairs. Th scene have a 2 Coronalights + HDRI.

[cecofuli]

Thanks Polymax. Here there isn't solid shadows cause a lot of lights and softshadows ;-)


Keymaster wrote in this thread: ad 1) Solid is darker sometimes, because there is bias added to prevent any fireflies by default. You can set Max sample Intensity to 0, eliminating the bias, but at cost of fireflies (which will eventually converge to the correct solution). Since there is no efficient way to render sun behind solid glass with path tracing, you would have to use for example bidir to get correct and fast results.

This remember me the old maxwell version with the famous "Sun shadow+Glasses" problem :(

And Solid is darker not only with sun, but with also normal Corona lights :(

[Polymax]

bidir/vcm not support absorbtion.

[cecofuli]

Yes, I saw...
But, transparent shadows for glass are so important!
 Why there isn't a good, robust solution in Corona? Do we have to wait some new version?

[Polymax]

At this point the solution of this problem does not exist in the Corona! ONLY fake(
And Vray will give also not correct shadows. There will help only caustic.
I hope bidir will be completed in the future!

[cecofuli]

And, how can we fake a transparent shadows!!  XD Impossible!
Keymaster has to do something for this problem ;-)
I add a new thread in the request section, ok?

EDIT: yes, I know. But I can do a transparent shadow with every method (BF, IM, LC, PPT. VRay-RT) . And for the 99% of our works, this is enough ;-)

[patoaltaco]

some test

[Polymax]

And, how can we fake a transparent shadows!!  XD Impossible!

hard fake: image with ground and 2sided shadows + image with chairs only (with alpha) in photoshop ... like this ;)