# How to create clear plastic? (Cycles)

I am trying to make a clear plastic material.

Here is what I have.

I am looking for something more like this. (but darker) Everything I try looks more like glass than plastic.

I have tried messing with just the refraction node and with the roughness of the shaders but it tends to look more "frosted" where the clear plastic has more of a soft/blurry reflection.

Plus I found the IOR of clear plastic is 1.4 but from looking at different reference pics it doesn't look like there is much refraction going on at all.

Any ideas?

• Either reduce the refraction way down, mix the glass shader with a transparent one, or if you want to keep things realistic add a solidify modifier to your mesh with a very low thickness value. Mar 1 '17 at 0:02
• @DuarteFarrajotaRamos ahhhh Adding a solidify modifier with an extremely low thickness seems to definitely make it look more plastic with my node set up. Thank you. I will play around with the settings some more but I think that was it. I didnt realize a solidify modifier would change so much on a closed mesh. I thought it was more for flat planes. I will wait to see if anyone comes up with something then I will answer with my node set up. Thanks again. Mar 1 '17 at 0:15
• @icYou Yeah, you need a solidify modifier. Mar 1 '17 at 0:32

This is very similar to the thin glass problem. It can be fixed by giving it a thickness, (i.e. Solidify Modifier, as already sugested), which in some cases raises some topology problems, besides the doubled mesh. Or by faking the surface thickness by not using refraction at all. This last approach raises another problem: IOR inverts automatically on backside faces (which in this case should be treaten as frontside)... Luckly we can solve that.

Explanation:

When a light ray hits a surface with a refraction shader, the ray will be bent dued to the difference of the light speed from one side of the surface to the other. This speed difference is represented by the IOR and ruled by the Snell's law. When the ray is exiting that medium, the difference of the light speed gets inverted, and so the IOR. Cycles does this automatically, and treats objects as solid (not hollow).

If we want hollow objects, we need to model both outer and inner surfaces of that object, and most of the times is exactly what we do. But there's a nice particularity from this phenomena: if both surfaces are parallel (at least where the ray enters and exits), the outgoing direction will be the same as the incoming direction; and thought the complete light path is not a straight line, the difference is quite small, sometimes smaller than the pixel size, and we can discard all that refraction calculation. A very good example of this are glass windows. In 3D, we call this the 'Thin Wall' or 'Thin Glass' effect, and some renders even have a shader just for this purpose.

In Cycles we can do something similar (treat the surface as a thin wall and discard refractions), but we need to specifically tell the engine that the IOR from a face when viewed from the objects inside, is the same as from the outside.

The nodes in the 'Fixed Backside IOR' frame do exactly that: If 'Backside' is 0 (False), we get (1-0)*IOR+(0*1/IOR)=IOR; if it's 1 (True) then (1-1)*IOR+(1*1/IOR)=1/IOR. Cycles will invert this backface value internally and in the end it stays equal to the initial IOR.

After having the IOR fixed, we can deal with the Reflective/Transmissive sides of the Fresnel formula. I didn't use a complete transparent shader for the transmissive part, because the greater the angle between the incoming ray and the surface normal, the greater the distortion and absorbtion on the light on that path. I used the translucent shader to mimic that effect, but it's just an approximation.

• Your result is awesome, and thanks for sharing the node setup. But would you mind explaining what is happening in the node setup? Otherwise all people can do is copy what you did without really understanding how it works. Mar 1 '17 at 14:47
• @secrop can you plz send me the blend file of the above material.
– atek
Aug 22 '17 at 2:22
• @atek, I never got to save that file (I don't even use this method, since I've already a python node for this). Anyway, this is something one can rebuild in 5 minutes just by replicating the above setup. Aug 24 '17 at 15:53
• @Secrop yes maybe for u 5min or less im newbie learner so to search and find the right nodes and plug thats confusing
– atek
Aug 24 '17 at 15:55
• @atek, the blender's manual (as with any software!) is a good place to begin. Aug 26 '17 at 10:50