The modelling and simulation of deformable objects is a challenging topic in the field of haptic rendering between human and virtual environment.In this paper,a novel and efficient layered rhombus-chain-connected haptic deformation model based on physics is proposed for an excellent haptic rendering.During the modelling,the accumulation of relative displacements in every chain structure unit in each layer is equal to the deformation on the virtual object surface,and the resultant force of corresponding springs is equivalent to the external force.The layered rhombus-chain-connected model is convenient and fast to calculate,and can satisfy real-time requirement due to its simple nature.Simulation experiments in virtual human liver based on the proposed model are conducted,and the results demonstrate that our model provides stable and realistic haptic feeling in real time.Meanwhile,the display result is vivid.
To improve the accuracy and interactivity of soft tissue deformation simulation,a new plate spring model based on physics is proposed.The model is parameterized and thus can be adapted to simulate different organs.Different soft tissues are modeled by changing the width,number of pieces,thickness,and length of a single plate spring.In this paper,the structural design,calculation of soft tissue deformation and real-time feedback operations of our system are also introduced.To evaluate the feasibility of the system and validate the model,an experimental system of haptic interaction,in which users can use virtual hands to pull virtual brain tissues,is built using PHANTOM OMNI devices.Experimental results show that the proposed system is stable,accurate and promising for modeling instantaneous soft tissue deformation.
虚拟现实技术中,纹理的力触觉表达通常需要提取纹理表面的高度轮廓特征,从而再现纹理的凹凸感,而图像纹理则反映的是纹理表面的二维灰度特征。提出了一种根据图像灰度信息恢复表面三维轮廓(shape from shading,SFS),并用于纹理的力触觉表达的方法。采用Tsai&Shah算法从二维纹理图像中恢复出表面三维微观形状,并用力触觉模型渲染。该方法无需专门仪器测量物体表面的微观轮廓,无需设计专用的纹理力触觉表达装置。实验表明该方法是可行的,并通过对实验结果的分析给出了改进方向。
