Erin Catto
@erincatto.bsky.social
I created Box2D. I enjoy all kinds of programming, but specialize in physics and animation. I work in Unreal for my day job (like everyone else). C/C++ and whatever Claude spits out for me. https://box2d.org/
When your graphics programmer tells you to stop simulating off-screen cloth, show them this video.
October 13, 2025 at 9:19 PM
When your graphics programmer tells you to stop simulating off-screen cloth, show them this video.
Pinched wrists on ragdolls are caused by twist bone poses living in the animation data. Twist bones are procedural and computed based on the pose of animated bones, so they should computed as a post process at runtime to fix this. See www.youtube.com/watch?v=Jkv0... by @bobbyanguelov.bsky.social
September 17, 2025 at 5:03 PM
Pinched wrists on ragdolls are caused by twist bone poses living in the animation data. Twist bones are procedural and computed based on the pose of animated bones, so they should computed as a post process at runtime to fix this. See www.youtube.com/watch?v=Jkv0... by @bobbyanguelov.bsky.social
Conventional wisdom is that you need a complex and expensive direct solver to handle high mass ratios and long chains.
Box2D has an iterative SoftStep solver that uses sub-stepping and soft constraints to handle high mass ratios and long chains.
Box2D has an iterative SoftStep solver that uses sub-stepping and soft constraints to handle high mass ratios and long chains.
April 6, 2025 at 5:46 PM
Conventional wisdom is that you need a complex and expensive direct solver to handle high mass ratios and long chains.
Box2D has an iterative SoftStep solver that uses sub-stepping and soft constraints to handle high mass ratios and long chains.
Box2D has an iterative SoftStep solver that uses sub-stepping and soft constraints to handle high mass ratios and long chains.
Compile Score is so good. This view lets me find out how vector is getting included, even implicitly. github.com/Viladoman/Co...
December 3, 2024 at 9:56 PM
Compile Score is so good. This view lets me find out how vector is getting included, even implicitly. github.com/Viladoman/Co...
The benchmark suite in Box2D has unlocked some easy optimizations. For example, how much should a bounding box be inflated? This is hard to answer without benchmarks. So I tried several values and ran the benchmarks for each one. Result is a 17% gain on this scenario and no regressions elsewhere.
November 12, 2024 at 5:45 PM
The benchmark suite in Box2D has unlocked some easy optimizations. For example, how much should a bounding box be inflated? This is hard to answer without benchmarks. So I tried several values and ran the benchmarks for each one. Result is a 17% gain on this scenario and no regressions elsewhere.