Cutting Simulation in Unity 3D Using Position Based Dynamics with Various Refinement Levels

Abstract

Augmented and Virtual Reality-based surgical simulations have become some of the fastest-developing areas, due to the recent technological advances and changes, in surgical education. Cutting simulation is a crucial part of the virtual surgery simulation in which an incision operation is performed. It is a complex process that includes three main tasks: soft body simulation, collision detection and handling, and topological deformation of the soft body. In this paper, considering the content developer’s convenience, the deformable object simulation, using position-based dynamics (PBD), was applied in the Unity 3D environment. The proposed algorithm for fast collision detection and handling between the cutting tool and the deformable object uses a sweep surface. In case of incision, the algorithm updates the mesh topology by deleting intersected triangles, re-triangulation, and refinement. In the refinement part, the boundary edges threshold was used to match the resolution of new triangles to the existing mesh triangles. Additionally, current research is focused on triangle surface meshes, which help to reduce the computational costs of the topology modifications. It was found that the algorithm can successfully handle arbitrary cuts, keeping the framerate within interactive and, in some cases, in the real-time.

An Effective Method for Slicing Triangle Meshes Using a Freeform Curve

“…Several methods [13][14][15] have explored virtual cutting tools for mesh manipulation. Khan et al [13] presented a method for cutting polygonal meshes.…”

“…Several methods [13][14][15] have explored virtual cutting tools for mesh manipulation. Khan et al [13] presented a method for cutting polygonal meshes. Their approach removes faces that intersect with the slicing plane defined by a virtual scalpel blade.…”

State‐of‐the‐art improvements and applications of position based dynamics

“…Lee et al solved simulation problems of tetrahedral models in Unity 3D with their proposed internal shape preserving constraint (ISPC) algorithm to integrate PBD with game techniques in Reference 67. Khan et al used PBD to simulate the correct physical behavior of deformable objects in Unity 3D environment in Reference 68. In the future, we expect to see more work in integrating PBD into other software packages including Maya, Unreal Engine, and Blender to help designers efficiently create visually plausible deformations for computer animation and games.…”

Octree cube constraints in PBD method for high resolution surgical simulation

“…However, in discrete models that model deformable organs, such as the FEM (finite element method) or mass spring models, this significantly increases the number of elements to be processed and breaks the real-time processing. To solve this obstacle, multiple resolution and adaptive mesh refinement models have been introduced in the related studies [1][2][3][4] to limit high resolution to the area where the degree of deformation is relatively large, such as where surgical manipulations are applied, or where the operator is gazing.…”

“…5 The PBD method is often used in CG animation due to its versatility and robustness, and has also been applied to organ models. 4,6,7 Position constraints in the PBD method are defined for each octree cube and applied to the vertices of the cube. In general, constraints based on the distance between two vertices are often used in the PBD method, but here we introduce constraints based on three-dimensional strain, called "cubic constraints," in order to obtain appropriate results even for large deformations.…”