In order to quickly calculate the optimal fitting position of the orthopedic plate on the surface of broken bone to reduce the repeated adjustment times of the orthopedic plate during the surgical operation, a rapid calculation method of orthopedic plate fit based on improved Iterative Closest Point (ICP) algorithm was proposed. Firstly, under the guidance of the doctor, the fitting area was selected on the surface of the broken bone, and the point cloud of the inner surface for the orthopedic plate was extracted by using the angle between the normal vectors of the surface points for the orthopedic plate. Then, the two groups of point cloud models were smoothed, and the grid sampling method was adopted to simplify the point cloud models, after these operations, the characteristic relationship between the point clouds was used for the initial registration. Finally, the boundary and internal feature key points of the inner surface point cloud model of the orthopedic plate were extracted, K-Dimensional Tree (KD-Tree) was used to search the adjacent points, so that the feature key points of the orthopedic plate and the selected area of the broken bone surface were accurately registered by ICP. Taking tibia as the example to carry out experiments, and the results show that the proposed method can improve the registration efficiency while maintaining relatively high registration degree compared with other registration algorithms proposed in recent years. The proposed algorithm can realize the rapid registration between different damage types of tibia and orthopedic plate, and it is universal to other damaged bones.

To solve the problems of interaction difficulty and low efficiency in traditional water flow heating simulation, a method about thermal motion simulation based on Smoothed Particle Hydrodynamics (SPH) was proposed to control the process of water flow heating interactively. Firstly, the continuous water flow was transformed into particles based on the SPH method, the particle group was used to simulate the movement of the water flow, and the particle motion was limited in the container by the collision detection method. Then, the water particles were heated by the heat conduction model of the Dirichlet boundary condition, and the motion state of the particles was updated according to the temperature of the particles in order to simulate the thermal motion of the water flow during the heating process. Finally, the editable system parameters and constraint relationships were defined, and the heating and motion processes of water flow under multiple conditions were simulated by human-computer interaction. Taking the heating simulation of solar water heater as an example, the interactivity and efficiency of the SPH method in solving the heat conduction problem were verified by modifying a few parameters to control the heating work of the water heater, which provides convenience for the applications of interactive water flow heating in other virtual scenes.

Serial plates are not reasonable in material saving and stress dispersion. To design orthopedic plates quickly and conveniently, a method to optimize plates through editing semantic parameters based on average bone model was proposed. Firstly, for reasonable distribution of serial plates in number and size, an average bone model with weights was created from the exiting bones. Secondly, a common orthopedic plate with semantic parameters was constructed based on average bone model and it could be conveniently modified and optimized. Finally, the thickness of the plate was optimized through finite element analysis and bisection strategy to meet the stress condition and use the least material. The experimental results show that the volume of the optimized femur clover plate and the Ⅲ type of the plate for distal femur is decreased by 2.7% and 12.2%, and the maximum stress is decreased by 56.9% and 24.4% respectively. Experimental results indicate that the proposed method can save material and disperse the stress of plates to effectively construct and optimize the orthopedic plates.

Concerning the problem of managing components information in the process of three-dimensional presentation of virtual assembly, a design of integrating 3-D visualization and information management technology combined with electric vehicles assembling and disassembling was proposed. Firstly, 3D model and information library were established according to the topology and supporting information of electric vehicles such as material and type. Secondly, a directory tree was created based on the parent-child relationship between the parts and sub-assemblies from information library, and three-dimensional presentation of the sub-assembly was achieved according to the principle that sub-assembly and scene tree have the same structure of "multi-tree", each node of the sub-assembly was animated before disassembly presentation. Finally, pickup interactive query and retrieving location query were achieved by combining the information management and visualization of electric vehicle. The constructed system was verified by century bird electric bicycle models, the integration of 3-D visualization and virtual assembly was realized, which could provide technical support for 3-D presentation and virtual assembly effectively. The experimental results show that the constructed system can effectively integrate the 3-D visualization and information management of components in virtual assembly.