The more sensory channels are equipped in a virtual assembly system, the more real users feel in the whole system, however, most of the existing virtual assembly systems are based on the natural interaction method of one or two sensory channels. Thus, this paper proposes a novel virtual assembly system integrating multi-sensory channels, including gesture interaction, Chinese speech interaction, tactile interaction, 3D display and real-time display of real environment pictures in the virtual environment. To improve the operability of the virtual environment, we analyze the parallel virtual assembly sequence on the basis of two-hand interaction, and the assembly priority is prompted based on UI interface. For ease of operation, we present a method of viewpoint control based on gesture interaction and the coordinate threshold of spatial position. A hierarchical bounding box collision detection algorithm based on volume difference is proposed to improve the efficiency of collision feedback and collision avoidance. In addition, the power equipment models are exhibited in the virtual scene, as the exhibits of the virtual roaming process. Finally, to evaluate the training effect of this system, a comparative experiment is designed to compare the participants’ experience and the effect of assembly training. The experimental results show that the virtual assembly system of natural interaction with multi-sensory channels is flexible and immersive.

Physical-based simulation technique has been widely used in creating astounding fluid appearances for film industries and computer games. However, stable and realistic fluid simulation based on Smoothed Particle Hydrodynamics (SPH) method is still challenging, as unstable solid boundary handling and numerical dissipation always plague current SPH fluid solvers. To solve these issues, we present a new method for improving SPH fluid simulation using position-based dynamics (PBD). For the stable fluidsolid interaction, by combining the position constraint solved by PBD and the relative contribution of solid boundary particles, we significantly alleviate the penetration issues at fluid-solid interfaces. And in order to stably simulate turbulence diffusion of SPH fluids, we enforce a novel nonlinear vorticity constraint on each fluid particle, and then solve it using PBD to smooth the vorticity field. The implementation results demonstrate that our method significantly improves SPH method for simulating realistic and stable animations of fluid phenomena.

In this paper, we put forward a real-time multiple GPUs (multi-GPU) accelerated virtual-reality interaction simulation framework where the reconstructed objects from camera images interact with virtual deformable objects. Firstly, based on an extended voxel-based visual hull (VbVH) algorithm, we design an image-based 3D reconstruction platform for real objects. Then, an improved hybrid deformation model, which couples the geometry constrained fast lattice shape matching method (FLSM) and total Lagrangian explicit dynamics (TLED) algorithm, is proposed to achieve efficient and stable simulation of the virtual objects’ elastic deformations. Finally, one-way virtual-reality interactions including soft tissues’ virtual cutting with bleeding effects are successfully simulated. Moreover, with the purpose of significantly improving the computational efficiency of each time step, we propose an entire multi-GPU implementation method of the framework using compute unified device architecture (CUDA). The experiment results demonstrate that our multi-GPU accelerated virtual-reality interaction framework achieves real-time performance under the moderate calculation scale, which is a new effective 3D interaction technique for virtual reality applications.

In order to extract the vortex features more accurately, a new method of vortex feature extraction on the Smoothed Particle Hydrodynamics data is proposed in the current study by combining rotation invariance and predictor-corrector method. There is a limitation in the original rotation invariance, which can only extract the vortex features that perform equal-speed rotations. The limitation is slightly weakened to a situation that the rotation invariance can be used, given that a specific axis is existed in the fluid to replace the axis needed for it. Therefore, as long as the axis exists, the modified rotation invariant method can be used. Meanwhile, the vortex features are extracted by predictor-corrector method. By calculating the cross product of the parallel vector field, the seed candidates of vortex core lines can be obtained, and the real seed points can be gained from the rotation invariant Jacobian. Finally, the seed point and a series of candidates based on the predictor-corrector method are connected to draw the vortex core lines. Compared with the original method, the rotation invariant predictor-corrector method not only expands the application scope, but also ensures the accuracy of extraction. Our method adds the steps of calculating the rotation invariant Jacobian, the performance is slightly lower, but with the increase of the particle number, the performance gradually tends to the original method.