Mobile interfaces are evolving towards touch-based approaches. This allows users to interact with their thumb directly on the screen. Such kind of direct approaches may be fussy for 3D interaction tasks, in particular because of thumb occlusions. In this paper, we introduce a new 3D user interface for the control of a planned trackball, where the users sketch horizontal or vertical movements to observe an object. A user study revealed no significant difference for error rate between this new approach and a standard trackball control. Despite a better completion time with the direct control, the study showed that the subjects preferred using the planned version of the trackball because it limits disorientation. Categories and Subject Descriptors I.3.6 [Methodology and Techniques]: Interaction techniques; H.5.2 [Information interfaces and presentation]: User interfacesInteraction styles Keywords 3D Rotation, User Study, Mobile Devices, Interaction Technique