Background: Virtual cutting of deformable objects plays an important role in many applications, especially in digital medicine, such as soft tissue cutting in virtual surgery training system.
Methods:We developed a novel virtual cutting algorithm, combined with mesh optimisation. A new local mesh processing method is used to control the number and quality of the elements created during the cutting process. At the same time, high-order tetrahedral elements are used to fit the cutting surface and reduce the mesh size.
Results:In this paper, single cut, multiple cut and intersecting cut are performed on the mesh model, combined with a force feedback device, and the result obtained is that the visual feedback is higher than 30 Hz, and the tactile feedback is 800~1000 Hz.
Conclusions:Experimental results show that the method proposed in this paper can effectively eliminate low-quality elements and control the mesh size, thereby ensuring real-time simulation.
K E Y W O R D Sdeformable objects, high-order element, mesh optimisation, virtual cutting
| INTRODUCTIONThe cutting simulation of physics-based deformable objects has always been an important research topic, and it has important applications in the fields of sculpture, computer animation, cloth simulation, crack growth simulation, virtual surgery and so on.Maintaining physical rationality during the cutting process and achieving stable and efficient simulation is still a challenging topic.Especially in virtual surgery, the soft tissue model needs to interact with surgical tools to achieve deformation and cutting and meet the requirements for real-time and authenticity of the simulation of real surgery. Therefore, it is essential to develop an efficient virtual cutting method.The current virtual cutting methods for deformable objects are mainly divided into mesh-based methods and meshless methods. This article focuses on mesh-based methods. The mesh-based virtual cutting method is mainly implemented through algorithms such as element deletion, 1 node snapping, 2 mesh subdivision 3-9 and virtual node algorithm. [10][11][12][13] The element deletion algorithm and the virtual node algorithm can achieve stable cutting realisation and they are easy to implement. However, element deletion and duplication will cause changes in the mass or stiffness of the model, which cannot satisfy the law of conservation of mass, and there will be a jagged surface during display. The mesh subdivision method can maintain the physical correctness of the model by dividing the mesh at the cutting track and can simulate the cutting surface correctly due to the adaptability of the tetrahedron. However, meshing will introduce a large number of additional elements, resulting in a substantial increase in computational costs. In addition, the division of tetrahedral meshes will inevitably introduce low-quality elements. The existence of low-quality elements greatly limits the ability of finite element calculations, thereby reducing the stability of cutting simulation.