Holl polycarb material help

[jjduncs]

Any suggestions for creating a material like Stevens favourite polycarb?

Im planning on a scene lit mostly through this kind of translucent wall plastic so would have to find a relatively quick to render shader.

Josh

Ref images below

[Ludvik Koutny]

If it's translucent material, then you could maybe use....  translucency.... ?

[jjduncs]

The panels are an extrusion with thickness.

They have a scattering type effect that diffuses the light that passes through.

Would translucency suffice for that?

I'll do some material tests tonight, just thought someone might have already tried their hand at creating this material.

[jjduncs]

Here is an example of the panels

[maru]

Why don't you try with translucency? In the reference pictures you posted, the effect looks like it could be achieved with translucency or with glossy refraction if you really need to be able to see what's behind the panels.

[Ludvik Koutny]

If you want best speed/quality ratio, then still... use translucency, and map it with texture of stripes, so it looks like those panel divisions are inside.

[jjduncs]

Alright I'll give translucency a try, thanks.

Should I still give the panel a thickness? or just single planes with mapped translucency..?

[jjduncs]

tried using two planes about 40mm apart, both with translucency and 0.1 refraction.

Seems to work fairly well.

It is a fairly crude test with the textures used from quick google search to see how well they would work.

With only 1 plane for the panels the light isn't diffused enough, while 2 does the trick.

Seems to render in a reasonable timeframe.

[maru]

Here are my tries. Ugly scene, one-sided translucent planes with bump map (gradient ramp). I think it works pretty well. There is also a second version with glossy refraction but it renders slightly slower (see file names).

[jjduncs]

Thanks Maru,

Those look good.

Bump map works well! If only there was a way to map translucency fraction as well.

are there any issues with using translucency and a small amount of refraction together? Ill test tonight and see how much time it adds to the renders. Mine above had only 0.1 refract.

I might stick to having 2 planes a few cm apart and having the hidden structure within them, for thats probably how it would be in my design (tho it would be two 20mm thick cellular polycarb sheets and a cavity between them and structure within that gap)

Another reason for having two planes, is that when I had a shadow cast onto the translucent plane from the outside, like an eave or tree etc, it would be a sharp defined shadow when looking from inside the building. Having 2 helps make this much more diffuse as it should be from within. Again, I'll have a look at how it affects the render times tonight.

Thanks again

[maru]

If only there was a way to map translucency fraction as well.

I thought there is in A7. No? Then it must be in newer versions so you can expect it in next public release.

[jjduncs]

Probably is! I'm still on a6. Will get A7 tonight and have a look.

[jjduncs]

got it sorted i think.

No need for anything except the gradient ramp like you used really.

[maru]

It depends on what level of detail you need but I think it looks ok in your tests.

[davius]

Most of the secret of a good polycarbonate panel relies on the Bump (besides the obvious translucency, as everyone else pointed out). Your images look good enough already, just little tweaks (variable transparency to emulate dirt) and it's perfect.