The use of a small texture containing a set of random offsets helps to blur the edges of the shadow better than what we might achieve with the standard PCF technique that uses a constant set of offsets. However, artifacts can still appear as repeated patterns within the shadow edges because the texture is finite and offsets are repeated every few pixels. We could improve this by also using a random rotation of the offsets within the fragment shader, or simply compute the offsets randomly within the shader.
It should also be noted that this blurring of the edges may not be desired for all shadow edges. For example, edges that are directly adjacent to the occluder, that is, creating the shadow, should not be blurred. These may ...
