Yu Zhang (张宇)

Experience

Awards at College

Baraff-Witkin Cloth Model with IPC Collision Handling

An implementation of the Baraff-Witkon cloth model. Unlike the original solver, our solver is based on a variational (optimization) formulation of the cloth model, and we solve this optimization problem using Newton's method. The IPC (Incremental Potential Contact) algorithm is used to handle the collision between the cloth and the rigid body.

Meshy - A 3D AIGC Project

Participating in the Meshy project as a graphics R&D engineer. Meshy is a 3D AIGC project that aims to generate 3D models from the text or image prompt. My responsibilities include optimizing the generateion quality and performance of the 3D generative model, and investigating various differentiable geometric representations, etc.

Classical Partial Differential Equations: Numerical and Exact Solutions

Several classical linear partial differential equations, including the transport equation, Laplace's equation, the heat equation, and the wave equation, are analyzed. Their exact solutions and numerical solutions (including Eulerian methods and Monte Carlo methods) in two-dimensional space are then compared.

Github Article

A Corrected Derivation of Invertible Neo-Hookean Model

In this project, we implement several different invertible constitutive models. Additionally, we correct the derivation of the invertible neo-hookean model, which is presented in the SIGGRAPH course 'Dynamic Deformables: Implementation and Production Practicalities'.

Github Article

2D Semi-Implicit MPM

We provide a detailed derivation of a 2D semi-implicit MPM (Material Point Method) time integration solver, and the experimental results are analyzed. Unlike other matrix-free methods (such as PCG), which avoid the explicit construction of stiffness matrices, we provide a full derivation for a 2D semi-implicit method and present the explicit form of the stiffness matrix.

Article Tutorial

High-Performance PBD Physics Engine

This project aims to develop a high-performance PBD (position-based dynamics) physics engine, which is similar to Houdini Vellum. The engine supports a series of materials' simulation: rigid body, soft body, fluid, cloth, granular material, etc. We achieve a 60 FPS's 240k particles fluid simulation, and the simulation can be extended to a large-scale scene (there are 20 million particles in the picture on the right side). To obtain a high-quality fluid surface, we implement a surface reconstruction algorithm based on dual contouring. In this project, we also use a CCD (Continuous collision detection) algorithm to tackle the tricky collision problem.

Dynamic Ball B-Spline Curves

Ciyang Zhou, Yu Zhang, Zhongke Wu*, Xingce Wang

Computer Graphics International 2023 (CGI 2023)

Dynamic Disk B-Spline Curves

Yu Zhang, Zhongke Wu*, Xingce Wang

33rd International Conference on Computer Animation and Social Agents Special Issues (CASA 2020)
Published on Computer Animation and Virtual Worlds (CAVW)   (Selected as the image of inside cover)

A disk B-spline curve (DBSC) is an extension of a B-spline curve and is used to represent a 2D region. DBSC is a useful 2D geometric representation and is widely applied in the 2D art design area, such as computer calligraphy, 2D computer animation, and nonphotorealistic rendering. To enhance the flexibility of DBSC, in this paper, we propose a physics-based generalization of DBSC -- Dynamic DBSC (D-DBSC), which extends the traditional DBSC in the time domain. We give the mathematical expression of D-DBSC and prove its several mathematical properties. We derive the motion equations of D-DBSC based on Lagrangian mechanics and investigate the motion equations when it is under linear geometric constraints. Last, a D-DBSC physical simulation system based on the finite difference method is presented.

Paper