A relatively small Min Depth value can bring the surface out of its own shadow, especially when combined with the Blend Offset value. The most typical example of this is a groundplane. If Min Depth is too high, shadows will not be cast from very close objects. This value determines the offset depth of the blended shadow samples, but not the depth of the center sample. As the value increases, the sample region becomes a cone with the outer edges towards the light.
Linear lights are initially two units long.
The length of a linear light can be changed using Xform Tool Palette Scale . The only parameter for Linear lights is Decay . Because of this sampling, Linear light shadows are more costly than point shadows. The increase in cost is proportional to the complexity of the scene and the length of the Linear light. The only parameter for Point lights is Decay .