Limits the directional light angle to steps of the given size rather than being a continuous value. This can prevent shadow shimmering if the directional light is slowly changing its angle, such as the sun moving across the sky. By default this is set to 0 which disables the step size and keeps the angle as a continuous value. Values in the range 0.1 to 2.0 seem to work best. This only applies if the SetShadowMappingMode is set to Uniform.
SetShadowLightStepSize( step )