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Realtime Wave Buoyancy

Real-time buoyancy in Unity and C++, with adaptive clipping on Gerstner waves. Final project for KTH's DH2323 Computer Graphics and Interaction course.

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Accuracy validation

Tested the integrator against known answers. Force error is float noise, tilt settles at 26.565°, and the paper's torque formula sticks at 45°.

  • C#
  • Unity
  • Buoyancy
  • Testing
  • Hirae
  • Validation

Evaluation of performance, perception, and the final call

Dropped 100 spheres into the waves. Linear holds 363 FPS, adaptive falls to single digits, mostly trig calls and garbage collection.

  • C#
  • C++
  • Unity
  • Buoyancy
  • Performance
  • Evaluation

Burst-jobbing the wave sampler

Wave sampling was eating the frame. Moved that one loop into a Burst job and went from 50 fps to 300–500.

  • C#
  • Unity
  • Burst
  • Jobs
  • Performance
  • Buoyancy

Curving the waterline

Bent the waterline to follow the actual wave instead of a straight chord. Found a bug on the way that made everything float a little too high.

  • C#
  • C++
  • Buoyancy
  • Physics
  • Unity

Multiple bodies, and making them not explode

Dropped the Stanford bunny and dragon in the water. The bunny flew off the map, the dragon hovered above the waves, and 30k triangles was too slow.

  • C#
  • C++
  • Buoyancy
  • Physics
  • Unity
  • Performance

Waves, finally

Catlike Coding's Gerstner waves are in, and the DLL stops pretending the water is flat at y=0.

  • C#
  • C++
  • Buoyancy
  • Physics
  • Unity
  • URP
  • Shader

Dampning

Implemented Hirae's angular momentum damping, and learned why damping angular velocity directly is wrong.

  • C++
  • C#
  • Buoyancy
  • Physics
  • Unity
  • Rigidbody

The actual buoyancy math

Implemented Hirae's closed-form surface pressure integration, triangle clipping, and got a cube to float correctly with proper torque.

  • C++
  • GLM
  • Buoyancy
  • Physics
  • Unity

Getting C# and C++ to talk

Got C# calling into a C++ DLL over P/Invoke and a cube floating on a hardcoded 100N. Most of the day went to interop nonsense.

  • C#
  • C++
  • P/Invoke
  • Unity
  • DLL

Setting things up

Got the repo set up, CMake working, and a cube floating in Unity. Kind of.

  • Setup
  • C#
  • Unity
  • CMake
  • Buoyancy

DH2323 Project Specification

My original DH2323 proposal for a real-time buoyancy simulation in Unity, based on Hirae's closed-form integrator and an adaptive curved clipping idea for waves.

  • buoyancy
  • physics
  • C++
  • Unity
  • simulation