pro calculate_incidence_angles,planet,pl_center,phase_angle_deg, $
			subsolar_azimuth_deg,polar_r_versus_equat_r,norm_ring_plane,inc_angles_rad

	;create a 3d_planet(n_pixels_x(planet),n_pixels_y(planet),3)
	;with 3d vectors of half-ellipse
	@~\lightning\idl\iss\scattered_light\get_three_d_planet.pro

	sz=size(planet)
	nx=sz(1)
	ny=sz(2)
	inc_angles_rad=planet

	;go 3-D to calculate all the angles
	;x-east in the imageplane,y-north,z-toward the spacecraft
	@~\lightning\idl\iss\scattered_light\solar_direction.pro

	for ix=0,nx-1 do begin
	for iy=0,ny-1 do begin
		r=transpose(three_d_planet(ix,iy,0:2))
		if (norm(r) ne 0) then begin
			;go 3-D to calculate all the angles
			;print,[ix,iy]
			;print,solar_direction##transpose(r_xyz)
			norm_planet=transpose(three_d_planet(ix,iy,3:5))
			inc_angles_rad(ix,iy)=acos(solar_direction##transpose(norm_planet))
		endif else begin
			inc_angles_rad(ix,iy)=-1 ;denotes imvalid pixels
		endelse
	endfor
	endfor
	;tvscl,inc_angles_rad,14
end