Now that we covered the basics of shadow casting with the different light sources, we can extend the fixed penumbra PCF implementation to support varying penumbra size.
We will be using a technique called percentage-closer soft shadows (PCSS). The technique will be presented through the spot light, but it can be used with point light sources. Although you can get this technique to work with directional shadows, it won't make much sense. This will be further explained in the How it works... section.
For this recipe, we will be using the exact same setup we had in the spot light shadow recipe. Note that we will need to take more samples from the shadow map in order to generate the wider penumbra areas, so it is recommended to use a larger shadow map than you would use with the fixed penumbra shadows.
If you may recall, the introduction to this chapter mentioned that the light source size affects the penumbra size. However, none of our light sources...