Optimise Shadows In Unity

There are a few things you should do to optimise the shadows inyour game:

Use lightmapping heavily to compute the shadows for static meshes.Unity has a builtin lightmapper. See http://docs.unity3d.com/Documentation/Manual/Lightmapping.html andhttp://docs.unity3d.com/Documentation/Manual/OptimizeForIntegratedCards.html.

The computation of dynamic lights have 3 main aspects and each onemust be tweaked for performance: the light itself, the casters andthe receivers.

To make a dynamic light, set Hard Shadows or Soft Shadows in it.However, the number of dynamic lights should be minimal since eachone issue additional rendering for shadow projection. Also, SoftShadows require a blur filter to ensure smoothness, which canimpact the performance. Finally, the resolution of the shadowtexture also affects performance. Seehttp://docs.unity3d.com/Documentation/Manual/Shadows.html andhttp://docs.unity3d.com/Documentation/Manual/DirectionalShadowDetails.html.

To make a mesh receive or cast shadows, set Receive Shadows or CastShadows in the respective Renderer (BEWARE:by default these settings are on). However, the number ofcasters and receivers should also be minimal, since each caster orreceiver in the "light frustum" must be rendered additional times.See http://docs.unity3d.com/Documentation/Manual/ShadowTroubleshooting.html.

Another related performance tweek is to use the Deferred RenderingPath instead of the Forward Rendering Path.

In summary:

1. Bake light maps;
2. Keep the number of dynamic lights to a minimum;
3. Tweak the resolution of the shadow texture;
4. Tweak the filter for Soft Shadows;
5. Use Receive Shadows and Cast Shadows judiciously;
6. Use the Deferred Rendering Path.