#ifdef RCSIDS
static char rcsid[] = "$Id: glass.sl,v 1.8 1998/09/18 23:09:29 lg Exp $";
#endif

/*
 * glass.sl -- Shiny reflective & refractive glass, using ray tracing.
 *
 * DESCRIPTION:
 *   Makes semi-transparent glass, using ray tracing to calculate
 *   reflections and refractions of the environment.
 * 
 * PARAMETERS:
 *    Ka, Kd, Ks, roughness, specularcolor - The usual meaning
 *    Kr - coefficient for mirror-like reflections of environment
 *    Kt - coefficient for refracted transmission
 *    transmitcolor - color of the glass
 *    eta - the coefficient of refraction of the glass
 *    reflectblur - how blurry are the reflections? (0 = perfectly sharp)
 *    refractblur - how blurry are the refractions? (0 = perfectly sharp)
 *    samples - set to higher than 1 for oversampling of blur
 *    reflectsamples, refractsamples - individual settings
 *
 * AUTHOR: written by Larry Gritz, gritzl@acm.org
 *
 * $Revision: 1.8 $      $Date: 1998/09/18 23:09:29 $
 *
 */


#include "locillum.h"
#include "rayserver.h"
#include "raytrace.h"



surface
glass ( float Ka = 0.2, Kd = 0, Ks = 0.5;
	float Kr = 1, Kt = 1, roughness = 0.05;
	float reflectblur = 0, refractblur = 0, eta = 1.5;
	color specularcolor = 1, transmitcolor = 1;
	float samples = 1, reflectsamples = 1, refractsamples = 1; )
{
    color ev = 0;            /* Color of the environment reflections */
    color cr = 0;            /* Color of the refractions */

    vector IN = normalize (I);
    normal Nf = faceforward (normalize(N), I);

    /* Compute the reflection & refraction directions and amounts */
    vector Rfldir, Rfrdir;   /* Smooth reflection/refraction directions */
    float kr, kt;
    fresnel (IN, Nf, (I.N < 0) ? 1.0/eta : eta, kr, kt, Rfldir, Rfrdir);
    kt = 1-kr;   /* Physically incorrect, but portable */
    kr *= Kr;
    kt *= Kt;

    /* Calculate the reflection color */
    if (kr > 0.001) {
	ev = kr * RayTrace (P, normalize(Rfldir), reflectblur, 1,
			    max(samples,reflectsamples));
    }

    /* Calculate the refraction color */
    if (kt > 0.001) {
	cr = kt * RayTrace (P, normalize(Rfrdir), refractblur, 1,
			    max(samples,refractsamples));
    }

    Oi = 1;
    Ci = ( Cs * (Ka*ambient() + Kd*diffuse(Nf)) +
	   specularcolor * (ev + Ks*LocIllumGlossy(P,Nf,-IN,roughness,0.5)) +
	   transmitcolor * cr );
}