This thesis presents a motion planning method that integrates a user input into the planning loop to find a path and animate a virtual character. After a general introduction, a general presentation of the motion planning problem is made and the most known algorithms are presented in the second chapter. Then, two works on which this chapter is based are presented in details. A new motion planning method designed for planning in human environments is described. Several tests and a study are made on different environments and show the advantages of the approach. The third chapter introduces a new interactive motion planning method that allows a human operator and an algorithm to cooperate in a single interaction loop. This method is based on ...