Kalwall Material

[Macker]

I've been trying to create a Kalwall material within VRay and am having some minor success, but still not generally achieving the effect that I want.

Basically Kalwall is a translucent building material that creates really diffuse lighting within buildings Click for examples

I've been toying around with the translucency effect within the VRayMaterial and also the SSS2 shader, but I'm still not achieving the lighting I want - generally I've not had much experience with SSS shaders within architecture though, so this is probably why. I've attached a picture of the closest result I've got.

As you can see the actual material itself looks fairly close to what I want to achieve, however the shadows aren't anywhere nearly as diffuse as they need to be. The lighting setup is simply a Vray Sun & Sky system with a Vray Plane to stop light from underneath the building. the Kalwall itself is 50mm thick (around what it would be in real life, give or take 15mm, depending on the manufacturer you use).

Any ideas on how to achieve the soft shadows? I'm not looking to change the lighting setup to fake it - you wouldn't in reality, plus if I were using this on a shot where there were also normal windows where I wanted fairly hard shadows it would be very difficult to fake. The closest I've got so far to the soft shadows is turning off "affect shadows", but this doesn't look too real either - physically correct is what I'm after.

[Morne]

hmmm i would say your refraction colour is too white, Maybe make it a bit more grey (this will make the light penetrate less through your material), then lighten your diffuse to compensate for the darker colour you will now get from less refraction.
Then the 0.6 on refraction is about right

Then play with the fog colour and fog multiplier to get the look you're after
(and I would try these settings with translucensy set to default)

Post your results so we can see

[Macker]

The reason for the refraction being pure white is as illustrated on pages 48 & 49 of the Arch & Design manual; http://www.mentalimages.com/fileadmi...and_design.pdf

Yes, I'm aware that it's a different render engine but my understanding is that implementation is much the same and that the fog colour will attenuate light as it travels through the medium, thus the thickness of the medium comes into play - as it would in the real world.

The part i'm struggling with more than anything is getting the lighting to actually diffuse through the wall, rather than travel straight through it and cast harsh shadows.

[tricky]

Could it be your IoR being 1.05? Doesn't that mean the light travels through almost unaffected? Maybe up that to 3 or 4 and see what happens?

[Macker]

Will give that a go.

[darbo]

You're right that the shadows are all wrong. I suggest you think more about how Kalwall functions as a diffuse light shade and emulate that rather than trying to be physically precise. In an interior environment Kalwall does essentially the same thing a lampshade does; the main visual difference is that it's hard, smooth, and is somewhat reflective. If you need it, do a google search for how to create lampshades in Vray (using Vray two-sided material) make it somewhat glossy and you should easily be able to replicate Kalwall.

From the Vray manual: http://www.spot3d.com/vray/help/200R...vray2sided.htm

[flino2004]

on top of what darbo said, if you need more definition for the softshadows after using Vray2sided you always can use vraylight behind (no visible) with "Skylight portal" (excluding Kalwall panels).

Fernando

[Macker]

Could it be your IoR being 1.05? Doesn't that mean the light travels through almost unaffected? Maybe up that to 3 or 4 and see what happens?

Tried it, didn't change the result.

As for using the 2sidedmtl, it gives more/less the same results as the setup I have now (with affect shadows turned off). Plus if I gave the base material any refractivity it took me back to square 1, with sharp shadows. Surely a SSS material should scatter light upon exit of the material?

[Macker]

These are my results of playing around with the Vraymtl SSS effect. Ended up just leaving it with "affect shadows" off.