no taboo
it's because shadows in blockland are stored in separate depth arrays based on how far away from the viewpoint a fragment is
it uses various factors to calculate the correct array and the "offset" in it which are extremely difficult to get right
when not getting them right either sudden changes (like that), shadow acne or peter panning happens
to quote the code
// fudgeKey is very hard to get right.
// Try various values to fix weird patterns or "disconnected shadows".
// It depends on your shadow quality, too.
const float fudgeKey = 0.1f;
const float fudgeKeyMult2 = fudgeKey * 2.0f;
const float fudgeKeyMult3 = fudgeKey * 3.0f;
const float fudgeKeyMult4 = fudgeKey * 4.0f;
