[EADC]

Have a test scene with a transparent material and some emitters. Now the shadow of the pillar shows on the inside of the half sphere, but does not show (when i think it should) when looking from the other side. Anyone had this before, and how to solve this? Tried various materials but the shadow never shows up.

[JDHill]

Hi EADC,

I'll venture a guess that this material's transparency comes from the addition of a Nd=1.00 BSDF. If this is the case, then the pictures you show are correct, as the material consists of 2 basic components:

- the visible, opaque layer(s), which are showing a shadow when observed from the front, and blocking all light when seen from behind
- the invisible Nd=1.00 (i.e. 'vacuum') layer, which is in no case reflecting/refracting any light

Is this a good guess?

JD

[EADC]

Hi JD,

Good guess about the nd1.0 , so now i used a single dielectric layer nd 1.51 roughness 35, but the result is exactly the same. Dropshadow on one side, invisible from the other side. No clue what´s wrong.

Eric.

[JDHill]

Hi Eric,

Well, with that out of the way...now I had to think this over some, and I'm not sure that there should be a shadow on the other side. I can't think of any way in which light could bounce in order for there to be, other than the fact that real glass is not perfectly pure, or clean. It is certain that a portion of the light transmitted through real glass is coming from ambient reflections off of other media in and on the pane - when these are shadowed, they no longer have any source of light to reflect, and we can perceive the the shadow of the object which is obscuring them.

Your inclination to give the glass roughness also suggests that, at least sub-consciously, you had a similar thought on this, and tried to model a dirty surface using roughness - this won't work, as roughness just controls the diffusion of light's reflection from the surface.

So, there's my working theory...maybe some brighter minds will chime in and offer a correction.

JD

[Bubbaloo]

No brighter mind here, but have you tried using SSS? I think that will get you a shadow on the back. But... I don't think there would be a shadow on the back, either.

[EADC]

got it to work now, indeed with some sss.


skydome

backlight

backlight leftside

lights with skydome

lights only

The objective was to get a nylon like tent fabric that shows shadows when lit from the inside, and with some slight transparancy. Made a combination of the glossy paper from Rickyx and the curtain from kurt.

Need to tweek the transparancy and gloss, but finally getting there.

[Mattia Sullini]

A case where maxwell could be less physical and more tricky...SSS through single-poly surfaces would be great!

[cornetjr]

Could you post your material, I am trying to do the exact same thing with no success,

thanks in advance!

[EADC]

material is uploaded to the mxm gallery. Good luck with it!