What are the limits on a trial judge's questioning of witnesses in the presence of a jury?

eliciting facts material to a just determination of the cause.'" [Citations.] [] The constraints on the trial judge's questioning of witnesses in the presence of a jury are akin to the limitations on the court's role as commentator. The trial judge's interrogation "must be . . . temperate, nonargumentative, and scrupulously fair. The trial court may not . . . withdraw material evidence from the jury's consideration, distort the record, expressly or impliedly direct a verdict, or otherwise usurp the jury's ultimate factfinding power." [Citation.]' [Citation.]" (People v. Harris (2005) 37 Cal.4th 310, 350.)