Instructions

Features

• High performance Verlet rope physics
  • Runs entirely on the GPU
  • Simulate hundreds of ropes at once
    • Fresh AABBs for each rope are available on the CPU every frame
    • Updates to specific rope points may be sent to GPU every frame
• Collision resolution
  • Supports SphereCollider, CapsuleCollider, and BoxCollider with no extra effort
  • Supports mesh collisions by baking a mesh distance field
    • In scenes where this occurs, you may notice hitching
• Cloth Simulation
  • Also runs on GPU, sharing much the same code as the rope
    • Every collider type that rope supports is also supported by cloth
  • Each point is constrained with its eight (four cardinal, four shear) neighbors
  • Supports 32x32 (max thread group size) resolution
    • Higher resolutions produce artifacts, for now
  • Updates a vertex and index buffer every frame, keeping the cloth mesh up to date

Test Scenes

• Move your mouse to wrap the rope around pins.

• Freely modify the position and simulation parameters of cloth.
• Watch cloth collide with various shapes.

• No actual benchmark yet - just spawn a bunch of GPU simulated ropes.
• To see collisions, click the < and > arrows to change from "None" to "Sphere" or "Terry"

• This is very buggy and slow right now - I need to do a few fixes and some cleanup.
• Generate mesh distance fields from a curated selection of models, and see how they collide with ropes.
• Click on a voxel to open a window that will allow you to view each slice and texel of its volume texture.
  • Each octree leaf contains a volume texture that includes a gradient to the nearest triangle in the RGB channels, and a signed distance (after conversion) in the A channel.

Known Issues

• There is a crash to desktop bug that seems somewhat random.
  • It's difficult to reproduce, and might not actually be happening anymore.
• Collision resolution performance vs. meshes is poor
  • Too many unlikely colliders are being tested.
• Mesh distance field build issues:
  • Performance tanks with high vertex counts
  • Build jobs are blocking the main thread more than is necessary
  • There are still large seams and cavities in many models

Post-Contest Plans

• Library
  • Easy to use VerletRope and VerletCloth components
  • Allow different segments of rope to connect with each other
  • Run rope simulation in the editor window
    • Bake initial rope positions
• Rope Physics
  • Rope points may have mass
  • Allow some points to be flagged as accessible on CPU
• Mesh Distance Fields
  • Allow volume textures to represent an arbitrary size in worldspace.
    • Currently each volume texture is just 16^3 world units.
  • Optimize in-game bake process
    • The current solution scales very poorly with triangle count.
  • Cache large mesh distance fields to disk
  • Allow baking in editor, shipping prebaked mesh distance fields
  • Raymarched debug visualization