Hello NEvOI,

The penumbra width calculation is the following : lightSize * (zReceiver - zBlocker ) / zBlocker . Effectively, the penumbra width is approximated by the distance ratio between the receiver & the blocker depth, modulated by a constant :

• The zReceiver depth is the depth of the fragment (in your shadow map) you are trying to shade
• The zBlocker depth is the average depth (in your shadow map) around the receiver fragment.
• The lightSize will be a fixed constant in world-space.

Put simply, the further apart zReceiver and zBlocker are, the bigger the penumbra - similarly, as zReceiver tends towards zBlocker, the penumbra width will tend to 0.

I am not sure where you got sizeWindowSample from, but I have had good results, with just this simple formula above. The papers you mention calculate a dynamic search width based on various parameters but aren't really needed to get it working : a fixed search width does the trick.

Hope this helps?