International audienceRotating 3D objects on desktop computers with a mouse or a trackpad is a notoriously difficult task, especially for novice users. Techniques relying on a “virtual trackball” have been proposed in the literature and these continue to be used in most 3D software. While several studies were conducted to compare the performance of these techniques, none was focused on the intrinsic parameter of the radius of the virtual control sphere of the trackball. We present the results of a controlled study to investigate the influence of the radius of the control sphere on the performance and behavior of users in a 3D docking task. Surprisingly, the results do not suggest a significant effect of the size of the virtual control spher...