Ray-Trace Bias

On the right, increased map bias makes the dog appear to float.

A single parameter, Ray-Trace Bias, affects the generation of ray-traced shadows. You set this parameter in the Shadow Parameters rollout.

The Ray-Traced bias control in the Shadow Parameters rollout moves the shadow toward or away from the shadow-casting object (or objects). By default, this value is 1 unit.

Increasing the bias moves the shadow away from the object, and decreasing the bias moves the shadow closer to the object. The Ray-Trace Bias value can be any positive floating-point number.

For example, if a shadow-casting object intersects another object but its shadow doesn't meet properly at the intersection, the bias is too high. This effect varies with the angle of the spotlight to the object. Extremely shallow spotlight angles usually require higher bias values.

Another purpose of bias is to avoid problems with objects that cast shadows onto themselves. If you see streaks or moiré patterns on the surface of the object, the bias value is too low.