Real-time Surface-based Volume Constraints on Mass-Spring Model in Unity3D

This paper describes a parallel method to simulate real-time 3D deformable objects using volume preservation constraints on a mass-spring model (MSM) to achieve plausible results in real-time performance. Instead of considering a volumetric mesh which is mostly used to simulate deformable objects, we purely take the surface of the 3D object into account to reduce the time complexity and obtain a high-quality deformable. In the conventional MSM, we can simply control the shape of the deformable object through the stiffness and damping coefficients which is beneficial for our volume constraint. We use the divergence theorem and implicit constraint enforcement scheme to maintain the volume of the object and deform it freely. The surface-based volume constraint is applied to correct the force of the spring network. The proposed algorithm was designed on compute shader in Unity3D and runs outside the normal rendering pipeline in the graphics processing unit (GPU) in order to utilize the massive parallel process to accelerate the performance of the simulation. The performance of the simulation can be accelerated by using the parallel processing method on the GPU with an average speedup factor of 4.27 using the conventional mass-spring method, and an average speedup factor of 2.54 for the volume preservation constraint method. We present several scenes which demonstrate the volume-preserving deformations using the conventional mass-spring method and volume-preservation constraint method and the volume loss of deformable objects for all 3D models is compared. The volume preservation method obtains a volume loss significantly lower than the conventional MSM for all experimental tests.