shadowCasterOverflowCount property

How many lights asked to cast a shadow last frame but got no slot in the shared shadow atlas, which caps shadow-casting spots and point lights separately (see kMaxSpotShadows and kMaxPointShadows).

Those lights still light the scene; they just throw no shadow, silently. A nonzero value means the scene asks for more shadowed local lights than the atlas holds, so some authored shadows are not being drawn.