button.lens Lens button.source Source button.clear Clear All button.object Object button.active Clear Active button.mirror Mirror button.aperture Aperture button.beam Beam label.angle Angle: label.spacing spacing = label.spread spread = label.anglevalue angle = label.rayinc rayIncrement = label.rayslope raySlope = label.opening opening = label.top top = label.bottom bottom = label.index_error ERROR: n2<1.0 label.focal_length fl =