The enhancement of computer tools becomes more dependent on the improvement and development of new human-computer interfaces than the increase in the power of machines. Input devices and interaction techniques are a constitutive part of human-computer interfaces and are at the heart of our works. Our research is part of this line of development of human-computer interaction and considers hardware, software and human capabilities related to human-computer interfaces. In this context, we highlighted the importance of transfer functions for indirect interaction. By taking into account the physical characteristics of input devices, user capabilities and by reconsidering the management of input devices in current systems we have shown how to improve existing tasks and perform tasks previously impossible to do with standard interaction techniques. In the context of direct interaction we have shown how hand occlusion can be accomodated to improve interaction with touch screens, while a better understanding of the capabilities for separating and integrating degrees of freedom can improve 3D manipulation tasks on multitouch screens. The development of new human-computer interfaces is also at the heart of our work. The limitations of existing elastic and isotonic devices led us to develop an hybrid isotonic-elastic device called RubberEdge. Our work also focuses on the use of tactile feedback with programmable friction to develop new interaction techniques, improve mode switching on touch screens with the development of an input device called Conté and the use of the interaction on and above an interactive surface with Mockup Builder. The last part of our work concerns the estimation of the perceived difficulty of pen gestures and the trajectory and kinematic gesture analysis to discriminate between select, pick and release tasks with free-hand interfaces.
