A spot light is defined by two light cones. The intensity of the light drops gradually to zero between the inner and outer angles. A spot light source is often quicker to render than a point light or a distant light because the illuminated area is more compact.
Spot light specific options:
Angle1, Angle2: - The angles that define the spot beam. The greater one of the two angles defines where spot illumination ends. Illumination fades from the full intensity to zero between the two angles. If the angles are equal, the spot light beam has a sharp edge.
Material - This control includes a list of the fog like materials of the current material library. Selecting a material will render a fog cone that matches the spot beam. This provides an easy way to make the spot beam visible.
Size - The radius of the light source. Size is used when computing mapped shadows. It is also used for ray traced smooth shadows i.e. when 'Quality' is greater than 0. The higher the size, the smoother the shadows become.
Quality - The sampling quality for ray traced smooth shadows. A high quality value increases rendering time but creates smooth shadows, whereas lower values render quickly but may introduce some dithering artifacts at shadows edges. The bigger the light source size, the higher quality value is needed for a proper quality.