Abstract: Haptic rendering broadens the application fields of virtual reality extensively.Simulating the behavior of deformable objects becomes a core challenge in haptic rendering,which demands the trade-off between the real time interactivity and the realism.In this paper,we classify various physically-based deformable models that have been developed,including mass-spring models,linked- volume models,finite-element-method models,boundary-element-method models,point-collocation models,tense-mass models,and hybrid models.The basic principles,advantages and disadvantages of those models are presented respectively.Finally,we carry out a comparison of these models and also suggest directions for the future investigation.