/*	spot light source shader
 *
 * 	Pixie is:
 * 	(c) Copyright 1999-2003 Okan Arikan. All rights reserved.
 */

light spotlight ( float intensity = 1;
                  color lightcolor = 1;
                  point from = point "shader" (0,0,0);
                  point to = point "shader" (0,0,1);
                  float coneangle = radians(30);
                  float conedeltaangle = radians(5);
                  float beamdistribution = 2; ) {
	uniform vector axis = normalize(to-from);

	illuminate (from, axis, coneangle) {
		float cosangle = (L . axis) / length(L);
		float atten = pow (cosangle, beamdistribution) / (L . L);
		atten *= smoothstep (cos(coneangle), cos(coneangle-conedeltaangle),cosangle);
		Cl = atten * intensity * lightcolor;
	}
}