cascadeOverlap property
Fraction of each cascade's shadow tile, measured inward from its edge,
over which it cross-fades into the next cascade, from 0.0 to 1.0.
0.0 (the default) hands off hard, so a fragment takes the first cascade
whose tile contains it and the resolution change can read as a seam.
Larger values soften that seam; each cascade also widens past its split by
the same fraction of its span, so the blend band is genuinely covered by
both. 1.0 blends from the tile center outward. Fragments inside the band
cost a second cascade lookup.
Implementation
double cascadeOverlap;