• _axes : transformations::Arcball
• _axis : transformations::Arcball
• _center : transformations::Arcball
• _constrain : transformations::Arcball
• _qdown : transformations::Arcball
• _qnow : transformations::Arcball
• _qpre : transformations::Arcball
• _radius : transformations::Arcball
• _vdown : transformations::Arcball