In the rendering pass, for each fragment we first lookup the depth map to decide whether the fragment is in shadow.For those not in shadow, we lookup the penumbra map to get the penumbra value.

• 第三遍分别查询深度图和半影图，确定场景的本影区以及半影区中像素的亮度，从而得到面光源照射下场景的近似软影效果。