[Radiance-general] water simulation

[Gregory J. Ward]

Hi Ignacio,

Your problem stems from the fact that your modified angles do not  
obey reciprocity, which says that if you reverse the ray (light)  
direction, then the angles remain the same on either side.  Both  
prisma and prism2 require this property to function.  Implementing  
Snell's law correctly, you should get a working material.

The vector version of Snell's law may be found in ray/src/ 
dielectric.c, or in an easier-to-read form on Wikipedia:

	http://en.wikipedia.org/wiki/Snell's_law

Note that the roles of the inside and outside indices of refraction,  
n1 and n2, reverse when you come from one side of the water verses  
the other.  The n of water is about 1.3, and air is of course 1.0.   
(OK, quibblers, air is really 1.0003)

-Greg

> From: Ignacio Munárriz <info at aisarquitectura.com>
> Date: May 10, 2006 5:04:50 AM PDT
>
> I'm trying tom model water with the prism1 & prism2 primitives.  
> I`ve been
> able to propagate the rays from sources using
>
>     ...