Shadow mapping normal-based bias.
Shadow caster surfaces are pushed inwards along their normals by this amount, to help prevent self-shadowing ("shadow acne") artifacts. Units of normal-based bias are expressed in terms of shadowmap texel size; typically values between 0.3-0.7 work well.
Larger values prevent shadow acne better, at expense of making shadow shape smaller than the object actually is.
Currently normal-based bias is only implemented for directional lights; it has no effect for other light types.
See Also: shadows, shadowBias properties.