Thank you for all your replies. I supposed to describe my question more detail. The problem I met is the performance of implement multi-lights shadow. For multi-lights we could use light pre-pass, deferred shading... to solve it. But for multi-lights shadow, for example in game there is N dot lights and one dynamic object. If each light has its own shadow for dynamic object, the performance will be a nightmare. As I know, UnrealEngine use some kind of resolution called "light environment". But the shadow quality is still not good.
So is there any other solution for implementing multi-lights shadow except limit light number or light cast shadow ability.
Thanks.