Two sided material or SSS for a car tarp or even shade canvas.

[Intuition]

I am trying to make a canvas like shader in which it has both SSS and two sided material properties.

Usually going the 2 sided material shader route for lamp shades and similar works quite well when the light is right behind the surface poly material.

Yet in this case I get translucency from the initial light hit from behind if there are any openings allowing the light to directly hit the back of the canvas/tent material but the model has many doubled up canvasses and I'd like to see the remaining light get through to the 2nd layer.

I realize this would require some rays getting through the first layer of polygons. I checked affect shadows as well. No change.

I can do the SSS material which gives me some back scatter but then not the shadows I'd like.

Any ideas how to double layer up two two sided materials?

Or create an SSS material that will show shadows on the backside?

Maybe this is a tricky layered material?

Open to ideas, surely what I am trying has been done before.

Thanks for any help in case I am over thinking this one.

The image attached is like the tent material but imagine two layers of this and the 2nd layer still getting good shadows and scatter through the first one.

[Intuition]

Here is a two layers together example.

[Morbid Angel]

try placing sss2 into 2sided mtl and use scatter gi option (with gi).

[snivlem]

Why use SSS? If the object has no thickness then shouldnt it just be only 2sided mtl?

[Intuition]

Its close. It still doesn't give me shadow definition from the first layer back to the second as much as I would like. I guess what I am trying to achieve is the idea that the canvas seams, which I have modeled into the geometry will create more of a shadow from the material facing the sun and the next layer behind it

Like this...



There is the option of glossy refraction. I suppose it is like that kind of effect but I am also trying to bring in the SSS. As seen in this pic. The second layer does pick up some light and shadow from the previous layer.

[snivlem]

Well could you just have a texture map for the translucency tex on the vray2sidedmat?

Darker = less light (for the lack of a better word) "transfer".
Lighter = more light transfer?

[Intuition]

Yeah the map would guarantee that the stitches would be darker in the SSS but doesn't give me any shadow definition from the first layer. Like if the two surfaces are close the shadow passing through the first layer is sharp and the further apart the get the shadow becomes softer as it hits the second layer. Like in the tent pic below.. Thanks for all the tips .

----UPDATE

A balance of diffuse and glossy refraction is really doing the trick. i do wish I could get a little more accurate shadow from the two layers but it does feel close now with glossy refraction mixed with diffuse.