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Hello, I’m Changyong ‍

Changyong Song | Ph.D. Student @ Vanderbilt | Physics-based Animation, Simulation, AI

Hello, I’m Changyong Song — or just CHAYO, if you prefer.

I dream of exploring and designing diverse virtual worlds that feel as expressive and dynamic as the real one.
Currently, my research spans visual perception, physics-based animation, and AI-driven simulation, with a focus on bridging low-level physical dynamics and high-level perceptual understanding. I work across multiple modalities—including video, simulation outputs, and temporal signals—to build intelligent systems that not only analyze motion, but also generate physically plausible, perceptually meaningful experiences.
Contact Me!
Email :
chang-yong.song@vanderbilt.edu
 LinkedIn :
www.linkedin.com
https://www.linkedin.com/in/chang-yong-song-b77862192/
 Media/Code:
Chayoso - Overview
Ph. D. Student @ Vanderbilt (23. Fall ~ ). Chayoso has 3 repositories available. Follow their code on GitHub.
https://github.com/Chayoso
Chang-Yong Song
Share your videos with friends, family, and the world
https://www.youtube.com/@chang-yongsong1997
Education :
Vanderbilt Univ. (2023. 8. ~ Current) Ph.D. Student, Computer Science
Korea Univ. (2021. 3. ~ 2023. 2) Master of Science, Computer Science and Engineering
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Thesis: MPM-Based Angular Animation of Particles using Polar Decomposition Theory
Kwangwoon Univ. (2015. 3. ~ 2021. 2) Bachelor of Science, Software
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Grade Scholarship: 6, 7th semester
CV/Resume :
Click [here] to download my full curriculum vitae.
Portfolio:
Click the image below to open the full PDF
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Publications

Proposal (Summary)

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Challenge: Hard to achieve both physical accuracy and visual fidelity in digital twins.
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Existing methods:
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Our idea:
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Work with;

PhaseBand-GS: Supplement Equations [pdf]

Equations.pdf
160.7 KB
Real-Time Digital Twins with Material-Aware Gaussian Splatting

Abstract

The primary contribution of this work is the first end-to-end framework for optimizing internal physics controls directly from image-space loss.
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Beyond Initial State Optimization: We move from optimizing what a simulation starts with to optimizing how it behaves throughout its entire duration.
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Appearance-Driven Physics Control: We demonstrate a powerful new paradigm where a high-level artistic goal (a target image) can be used to derive low-level physical controls (dFc) automatically

Technical Pipeline

Summary:
Our framework establishes a seamless, fully differentiable loop between a C++ physics core and a Python-based rendering and optimization frontend.
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Forward Physics Pass (C++):
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State Transfer (C++ → Python):
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Surface synthesis (From Sparse Volemetric Physics Sim to Dense Surface Physics Sim)
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Render with 3DGS and make the pipeline differentiable
Gaussian Morphing Animation

Isaac Sim–generated datasets meet an MLS‑MPM/CPIC cutting engine for physically grounded learning.

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Current result:
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Mesh → SDF Pipeline
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Colliders (Knife/Board)
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Elasticity/Plasticity
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MPM Kernels
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Rendering/Overlay
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CLI / Output
SDF Demos:
Demo video (MLS-MPM/CPIC for the Robot Cutting Sim) :
Learning to Cut: High‑Fidelity Simulation & Dataset for Robotic Cutting

Describe Lava’s localization with wax

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Use Numeric Animation for Real Data in Gen AI
Lava Localization Simulation Based on the Wax

TVCG Teaser Video:

Rendering results:
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Sphere to Bunny & Duck to Cow:
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D to Dragon:
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TVCG:
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Abstract :
A Differentiable Material Point Method Framework for Shape Morphing
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Abstract :
Rendering results:
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Sand particle example:
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Snow with Car:
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Primitive Rectangle (vs MPM):
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Snowflakes (Neo-Hookean):
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Mater’s Thesis: (Dissertation Defense: 11/17)
MPM-Based Angular Animation of Particles using Polar Decomposition Theory
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Grad School Projects
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Abstract:
Automated Verification of Neural Network-Based Image Classifier for Stability Assurance in Graphics Rendering
Abstract:
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We introduce a hybrid emotion recognition model that combines a pre-trained EfficientNet backbone with LSTM to capture the temporal dynamics of facial expressions. Unlike traditional static FER approaches, our model processes video sequences to classify valence and arousal into 21-level categories (from -10 to 10), enabling more accurate emotion estimation over time. The system is trained on the AFEW-VA dataset and outperforms baseline CNN-LSTM architectures, demonstrating the benefits of integrating spatio-temporal modeling in affective computing.

Results

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Compared to ResNet-50 baseline, our model improved the CCC score by over 60% (Valence: 0.31 → 0.97)
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EfficientNetLSTM achieved superior spatio-temporal representation despite smaller batch sizes and longer training time (7 hrs vs. 6 hrs)
Sequence-Based Facial Emotion Recognition using EfficientNet and LSTM

Compressible Flow Simulation using FEniCS

I implemented a simulation of compressible fluid flow using the finite element framework FEniCS. The governing equations include the full Navier–Stokes equations, accounting for variable density, momentum conservation, and thermal energy transport:
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Mass conservation: ∂ρ/∂t + ∇·(ρu) = 0
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Momentum equation includes both viscous and pressure forces with variable density
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Energy conservation: accounts for heat convection and conduction
I derived and implemented the weak forms of these equations to suit finite element analysis.
During simulation, we encountered numerical instability, particularly in the advection term. To address this, we plan to incorporate SUPG (Streamline Upwind Petrov-Galerkin) stabilization, which mitigates oscillations and enhances robustness in advection-dominated flows.
This approach is expected to improve both convergence and physical realism of the compressible flow model.
Compressible Flow Implementation with FeniCS
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Diffusion Model
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GAN
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Regression
Machine Learning Algorithms Implementation

Texture Volume Rendering with GLSL

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This project implements GPU-based volume rendering using GLSL. Rays are cast through a 3D texture volume, with AABB (Axis-Aligned Bounding Box) intersection used to compute entry and exit points for ray traversal. The renderer supports alpha blending for accumulating semi-transparent voxel colors and isocontouring for visualizing surfaces of constant intensity. The combined use of ray marching and transfer functions allows for flexible and efficient real-time rendering of volumetric datasets.
Volume Rendering using GLSL
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Working Experiences
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Develop and implement large-scale Gaussian splatting scene reconstruction processes to enhance visual accuracy.
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Integrate physics simulation layers, including fire modeling and earthquake effects, to create realistic disaster scenarios.
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Contribute to the advancement of technology linking digital twins with LLM-based disaster scenario generators, improving response strategies.
Computer Graphics/Vision Intern @ RescueSight Inc.

Responsibilities / Highlights

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Designed and implemented a GLTF-based physics engine that parses scene structures and physical properties directly from GLTF files.
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Enabled real-time simulation of rigid body dynamics by mapping GLTF node hierarchies to physical entities with mass, inertia, and collision shapes.
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Developed a custom parser to extract mesh, transform, and material data from GLTF assets for integration into the simulation pipeline.
Software Development Engineer Intern @ GrapiCar Inc.
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Undergrad School Projects
What I Built
Implemented various real-time physics simulations using OpenGL and Unity 3D , focusing on deformable bodies and cloth-like behavior using the Mass-Spring System.
Key Projects
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Cloth Simulation
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Sphere Deformation
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Spring-Mass System
Physics Simulation using Mass-Spring System & Deformation
What I Built
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Implemented natural cubic spline and B-spline curve algorithms from scratch for smooth curve interpolation and modeling.
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Developed an interactive system for curve construction, supporting user-defined control points and real-time visualization.
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Explored properties of different spline types such as continuity (C¹, C²), local control, and smoothness.
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Compared spline types through visual and mathematical analysis to understand their behavior and suitability in animation or modeling tasks.
Results:
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Natural Spline
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B-Spline
Curve Implementation
Overview
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Developed multiple graphics demos using OpenGL, demonstrating object transformation, lighting, and rendering techniques with various mathematical frameworks.
Core Features
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Object Transformation & Illumination
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Ray Tracing
OpenGL
Project Overview
Designed and implemented core gameplay elements in Unity 3D, including character motion, particle effects, and enemy AI behaviors.
Key Features
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Character Motion
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Particle Effects
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Raid Monster AI (Raid Hunter)
Unity 3D Game Development: Motion & Particle FX Design
Project Overview
Designed a fully immersive VR gameplay experience using Unreal Engine 4, focusing on monster pattern design, level/map layout, and player-environment interaction in a virtual space.
Key Features
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Monster Pattern Design
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Map / Level Design
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VR Mechanics
VR Game Design using Unreal Engine 4
Mission
Clear all dots within the time limit by strategically connecting same-colored dots.
What I Built
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Developed a real-time puzzle game inspired by Two Dots, where the objective is to reduce all remaining dots to zero.
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Implemented core gameplay mechanics: dot matching, chain elimination, combo detection, and time-based challenge system.
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Designed intuitive UI and grid system for visualizing dot connections using a custom rendering loop.
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Added mission tracking, real-time countdown, and animated feedback for player actions.
Two Dots-Inspired Puzzle Game
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Teaching Assistant
Subject Name
Duration of work
Institution
Computer Graphics
Open
2021/03/02 → 2021/06/25
Korea Univ.
C Language
Open
2021/03/02 → 2021/06/25
Korea Univ.
Computer Colloquium
Open
2021/03/02 → 2021/06/25
Korea Univ.
Special Topic
Open
2023/08/21 → 2024/12/06
Vanderbilt Univ.
Deep Learning
Open
2024/01/08 → 2024/05/01
Vanderbilt Univ.
Computer Architecture
Open
2024/08/22 → 2024/12/10
Vanderbilt Univ.
Aritificial Intelligence
Open
2025/01/07 → 2025/05/01
Vanderbilt Univ.
Seminars (Korean)
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Stormscapes: simulating cloud dynamics in the now (22. 5)
[220512]_PaperSeminar_.pdf
3074.1KB
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Simulating Fracture with Material Points (22.9)
[220901]_Paper_Seminar_Simulating Brittle Fracture.pdf
2734.8KB
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