maximumScreenSpaceError
The maximum screen space error used to drive level of detail refinement. This value helps determine when a tile refines to its descendants, and therefore plays a major role in balancing performance with visual quality.
A tile's screen space error is roughly equivalent to the number of pixels wide that would be drawn if a sphere with a radius equal to the tile's geometric error were rendered at the tile's position. If this value exceeds maximumScreenSpaceError the tile refines to its descendants.
Depending on the tileset, maximumScreenSpaceError may need to be tweaked to achieve the right balance. Higher values provide better performance but lower visual quality.