Towards building new, friendlier human-computer interaction and multimedia interactive services systems, new computer techniques are applied which aim at revealing information about the affective state, cognitive activity, personality, intention and psychological state of a person. In this paper we conduct a survey to recent developments and current state-of-the-art in the field of body analysis by the use of non-intrusive optical systems. Markerless based human motion capture describes the activity of analyzing and expressing human motion using image processing and computer vision techniques. In this paper, we categorize these approaches in the following four categories: Model-based methods, Region-based methods, Active contour based methods and Feature-based methods and present the advantages and disadvantages of each category separately.