{	New functions for calculating light transmission through prisms.

	R. Compagnon and F. Di Pasquale			(Spring 1992)
	LESO-PB
	EPFL
	CH-1015 LAUSANNE

	G. Ward modified for new fprism.c 6/30/93
}

{	function fprism(A1..A10) performs the calculations
	A1: length a of the prism panel
	A2: length b	" 
	A3: length c	"
	A4: length d	"
	A5: indice of refraction of the prism material 
	A6: fraction of the incident ray under which the ray propagation inside
	    the prism is aborted (0<A6<1)
	A7: indicates which face of the prism is covered by a metallic layer
	    1: face beta
	    2: face gamma
	    4: no face
	A8: reflection factor of the metallic layer (0<=A8<=1)
	A9: angle tolerance (in radians) for combining rays travelling nearly
	    in the same direction
	A10: angle tolerance (in radians) for assuming that a ray is directed
	     toward a source

	function fprism_val(a,b,c,d) is used to pick the necessary output values
	calculated by fprism
	a: selector for choosing which value we ask for:
			0: X direction of the ray
			1: Y     "
			2: Z     "
			3: transmission or reflection factor of the ray
	b: selector for choosing which kind of ray we ask for:
		       -1: a reflected ray is expected
			0: any ray (reflected or transmitted) is expected
			1: a transmitted ray is expected
	c: rank of the expected ray (1<=c)
}
tau1 = fprism_val(3,1,1);
dx1 = fprism_val(0,1,1);
dy1 = fprism_val(1,1,1);
dz1 = fprism_val(2,1,1);
tau2 = fprism_val(3,1,2);
dx2 = fprism_val(0,1,2);
dy2 = fprism_val(1,1,2);
dz2 = fprism_val(2,1,2);