New recording and replay feature added to Box2D. Uses determinism to exactly reproduce the simulation for your game. Debug your game with all details including ray casts and other queries. Deterministic rollback too. box2d.org/posts/2026/0...

Where are the Copilot productivity gains?

I added a native task scheduler people can use in Box2D. It is only 200 lines of C code. enkiTS is great, but having fewer dependencies is good for this project. It lets me run sanitizers more easily and have more control over performance. I'm still using Tracy for profiling.

This is the game I've been working on the last four years. It is an incredibly ambitious project made by a small team. www.youtube.com/watch?v=7fax...

Unreal has simple and complex collision. But sometimes a piece of collision is both. I'm now calling this "simplex" collision.

They removed programming from the GDC. I thought games are software.

When your graphics programmer tells you to stop simulating off-screen cloth, show them this video.

I'm an #IndieDev building a custom engine for my medieval fantasy survival game. Some things I've done so far: Simulation with client / server networking Basic DX12 renderer Asset pipeline Character movement and animation #ProcGen world creation Basic UI Basic Audio Basic Health / Combat

A couple barriers to C development are lack of a fast sorting library and a fast hash set and map. I've found these two libraries to be excellent at providing those. They are macro based, but I think the trade-off is worth it. Both work with C99. github.com/svpv/qsort github.com/JacksonAllan...

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

Silksong is using Unity? So using Box2D?

I love physics based walking simulations. I'm also pleased the author was successful using Box2D (v3.1?) www.youtube.com/watch?v=aBp-...

This video is great for teaching the basics of GJK. However, the approach is flawed for computing distance and only works for determining separation true/false. Unfortunately the author has disabled comments and people keep using this and ending up with broken code. www.youtube.com/watch?v=Qupq...

Box2D version 3.1 is released! Blog post: box2d.org/posts/2025/0... Release notes: github.com/erincatto/bo... Documentation: box2d.org/documentation/

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.

I’ll be speaking about Box2D optimizations at the #GDC2025. I’ll be diving into the details of implementing fast continuous physics. This presentation has a new format I’ve developed recently. I’m really excited to share it! schedule.gdconf.com/session/opti...

Tangent speed is a new Box2D surface property that lets you easily make conveyor belts or launch ramps like this. youtu.be/WUxqUSk79nE

Rolling resistance using a constraint so it works on ramps. www.youtube.com/watch?v=pRe6...

Compile Score is so good. This view lets me find out how vector is getting included, even implicitly. github.com/Viladoman/Co...

I spent a day debugging a Linux server bug for our game. Apparently code like this is undefined behavior and Clang may optimize it to garbage (but not always). struct Vec { float x, y, z; }; Vec myVec; int index = 2; return (&myVec.x)[index]; // UB

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.