5.6.2 Spotlights

If we add the keyword spotlight, then the light is restricted to a cone with tip at S and the line from S to P as axes. The half opening angle of the cone is given by the float R1 and the full prescribed intensity of the light is attained in the cone with the float R0 as half opening angle.

	light_source { S, rgb C 
	  spotlight point_at P radius R0 falloff R1 [ tightness T ] }

By setting the optional parameter tightness T to a value greater than 0 one can soften the light distribution exponentially.