Program Sketch for Ray Tracing

program raytrace
var	lsou; (* intensity of light source *)
	back; (* background intensity *)
	ambi; (* ambient light intensity *)
	depth; (* depth of ray tree consisting of multiple 
		reflection/refraction paths *)

	ray = record			    (* ray      x = a + ti
	      	point: (a, b, c)		     	y = b + tj
	      	direction: (i, j, k)	       		z = c + tk  *)
	      end;
        r: ray;

	function intensity (r);        (* intensity = spec + refr +dull
					  spec = specular reflection component
					  refr = refraction component
					  dull = non-reflecting, non refracting
					  component *)
	L: vector pointing to light source
	N: surface normal
	Objects [1...n] (* list of n objects in scene *)
	Ks [1...n]	(* specular reflectivity factor for each object *)
	Kr [1...n]		(* refractivity index for each object *)
	Kd [1...n]	(* diffuse reflectivity factor for each object *)

	(* Additional Comments: For a transparent object, Kd[j]=0 and 
		Ks[j]+kr[j]=1    i.e. partly reflecting + partly refracting
	   For an opaque object Kr[j]=0,  Ks[j] and Kd[j] can be anything 
	   as no simple relation between them *)

function intensity(r: ray): rgb
	var flec, frac: ray;	spec, refr, dull: rgb;
	begin
	  depth := depth +1
	  if depth >5 then intensity :=back
	  else
	    begin (* label 1 *) 
		check ray r for intersection with all objects in scene
		if no intersection 
		then if r parallel to L
		     then intensity :=lson
		     else intensity :=back
		else
		  begin (* label2 *)
		    Take closest intersection which is object[j]
		    compute normal N at the intersection point
		    if Ks[j] >0   		(* non-zero specular reflectivity *)
		    then begin
			   compute reflection ray flec;
			   spec := Ks[j]*intensity(flec);
			 end
		    else spec:=0;
		    if(Kr[j]>0)   		(* non-zero refractivity *)
		    then begin
			   compute refraction ray frac;
			   refr := Kr[j]*intensity(frac);
			 end
		    else refr:=0;
		    check for shadow;
		    if shadow
		    then dull:= Kd[j]*ambi
		    else dull:= Kd[j]*(lsou* N.L +ambi);
		    intensity :=spec +refr +dull;
	               end (* label2 *)
	    end( *label 1*)
	    depth := depth -1
end(* function *)


begin (* raytrace*)
	for each pixel P of projection viewport in raster order
	begin
	  r = ray emanating from viewer through P
	  set intensity(r) to the frame buffer pixel corresponding to P
	end
end (*raytrace *)