Le 18-07-19 à 17:28, bzigon a écrit :
> Hello
> I am trying to model objects made from polypropylene. The material
> is translucent (as opposed to transparent).
> 
> Here is a link that shows what the material looks like.
> 
>
https://www.webstaurantstore.com/cambro-30ppch190-1-3-size-translucent-polypropylene-handled-lid/21430PPCH.html
> 
> The povray material type I am using always looks clear. I can't figure out how
> to model the look of the material.
> 
> Here is what I have. Can anyone help?
> 
> #declare TranslucentPlastic =
>   material
>   {
>    texture
>    {
>      pigment{rgbf 1}
>      finish
>      {
>        diffuse 0.3
>        ambient 0.7
>        reflection{fresnel on}
>        phong 10.0
>        phong_size 60.0
>      }
>    }
>    interior
>    {
>      ior 1.5
>    }
> }
> 
> --Bob
> 
> 

The best way is to use subsurface light transport. Version 3.8 alpha or 
Uber-POV.

To use it, you need to activate it in the global_settings block :

global_settings {
   subsurface { [samples DiffuseScatteringINT, SingleScatteringINT] 
[radiosity BOOL] }
}

samples default to 50, 50
Use smaller to get fraster, but grainy, render.
radiosity defaults to OFF

Next, you need to add it to the finish block of the object :

subsurface { translucency COLOR }

COLOR can be a colour vector or a float.
The values are NOT limited to the  range.
If translucency is large relative to the object, then the object can 
look transparent.

The effect depends on the ior of the object and it's scale.
The scale can be set globally :
global_settings{mm_per_unit INT}

Where INT represent how many milimeters are in one POV unit.

When using translucency, you should avoid colour components of zero. 
Instead, use some very small values. Use rgb 0.001 instead of rgb 0 for 
your black.
DON'T use diffuse 0. It can cause a crash.

Use merge instead of union.
Meshes must be well beheaved and closed.
In a CSG, use a single object whide interior.


Alain

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