Le 18-03-09 à 09:45, muyu a écrit :
> Hi,
> 
> In Povray, the optical properties of each surface can be set by ambient, diffuse
> and specular. This is very flexible but only single value is allowed over
> color-channels. As a matter of fact, the optical properties of object often
> differs over wavelength or colors. I am wondering what's the assumption in
> Povary to deal with this. It will be great if you could recommend a reference to
> describe the raytracing theory used in Povray. Thanks a lot in advance.
> 
> Best regards
> Shouyang
> 
> 
ambient and emission can use a colour vector.

diffuse set the % of incoming light that get diffused by the material. 
Use a float. Using a colour vector here is not physically correct, use 
the pigment.

The pigment control the tint of the material. Use a colour vector, but 
you can use a single float for grey levels.

reflection control the amount of light that get specularly reflected. 
Use a colour vector or a single float. Can be set to use the fresnel law 
where the amount of reflection is dependent on the IOR of the object and 
the angle of incidence, or metallic where the pigment affect the colour 
of the reflection.

specular and phong control the highlights. Use a float. Adding metallic 
make the highlight take on the colour of the pigment.

The material can be more or less transparent. Controlled by the filter 
and transmit optional components of the pigment.

Most transparent object should have an interior statement to set it's 
ior, and optionally it's chromatic dispersion strength. When an object 
have an ior, total internal reflections are taken care of automatically.

A transparent object can affect the colour of light going through it 
using light fading, also set in the interior block.
Such an object can also be filled with some media that will greatly 
affect it's appearance.

You can use SSLT by adding "subsurface integer, integer" in the 
global_settings and adding subsurface{translucency<float,float,float>} 
to the object itself. A single float can be used for the object.

In all cases, if the light used is not white, it will greatly affect the 
colour of any object.

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