1. A method of controlling a virtual object within a virtual workspace, comprising: recognizing a hand posture of an initial touch gesture directed to a touch-input receptor; setting a mode constraint based on the hand posture, the mode constraint specifying a constrained parameter of a virtual object that is to be maintained responsive to a subsequent touch gesture; recognizing a subsequent touch gesture directed to the touch-input receptor; and modulating an unconstrained parameter of the virtual object responsive to the subsequent touch gesture while maintaining the constrained parameter of the virtual object in accordance with the mode constraint.