GPU-accelerated deformation mapping in hybrid organ models for real-time simulation

Surgical simulation is expected to be an effective way for physicians and medical students to learn surgical skills. To achieve real-time deformation of soft tissues with high visual quality, multiple resolution and adaptive mesh refinement models have been introduced. However, those models require additional processing time to map the deformation results of the deformed lattice to a polygon model. In this study, we propose a method to accelerate this process using vertex shaders on GPU and investigate its performance.

A hierarchical octree cube structure is generated from a high-resolution organ polygon model. The entire organ model is divided into pieces according to the cube structure. In a simulation, vertex coordinates of the organ model pieces are obtained by trilinear interpolation of the cube's 8 vertex coordinates. This process is described in a shader program, and organ model vertices are processed in the rendering pipeline for acceleration.

For a constant number of processing cubes, the CPU-based processing time increased linearly with the total number of organ model vertices, and the GPU-based time was nearly constant. On the other hand, for a constant number of model vertices, the GPU-based time increased linearly with the number of surface cubes. These linearities determine a condition that the GPU-based implementation is faster in the same frame time.

We implemented octree cube deformation mapping using vertex shaders and confirmed its performance. The experimental results showed that the GPU can accelerate the mapping process in high-resolution organ models with a large number of vertices.