The Rapier Physics Engine

Why do the readmes for physics engines rarely specify how they solve contact constraints? This is one of the most difficult parts of writing a physics engine. It might be less important if you're just interested in visuals and making it "look OK" in a videogame, but it has an impact on the dynamics, so especially if you're interested in robotics or accurate simulation of real-world physics, this is really important to specify.

Cross Platform determinism and great serialization capabilities makes this a networked physics programmer&#x27;s dream!<p>I kinda wish this was in cpp, so that I could integrate it with Godot and have it be considered for upstreaming.<p>Edit:<p>Wait, no ray cast? I&#x27;m confused why that wouldn&#x27;t be implemented. That&#x27;s a very simple operation, is it not?<p>No continuous collision detection is not so great either, but is okay if the performance is good enough to tick at a high rate.

A few months back I tried - and failed - to write a basic 2d physics engine for my JS canvas library. Before then, I tried to use existing JS physics engines with the library ... but none of them integrated nicely; the closest I got to making something useful was with Matter.js (see Codepen demo[1]).<p>Rapier has a WASM version, and JS bindings. I&#x27;m already looking forward to see if I can get the engine working with my code. Is there a JS-focussed community around Rapier where I can ask questions if I get stuck?<p>[1] - <a href="https:&#x2F;&#x2F;codepen.io&#x2F;kaliedarik&#x2F;pen&#x2F;zYvbwBy" rel="nofollow">https:&#x2F;&#x2F;codepen.io&#x2F;kaliedarik&#x2F;pen&#x2F;zYvbwBy</a>

- cross platform bit level determinism<p>- fully serializable state<p>Wow! Sounds like a boon for Javascript game engines like Bevy. I wonder if they&#x27;ll support PlayCanvas as well.

The benchmarks are pretty interesting. Why is it that nphysics has such apparent inconsistency in its frame times?

&gt; Cross-platform determinism: if the enhanced-determinism feature of Rapier is enabled, it will behave in a bit-level cross-platform deterministic way in all platforms that comply with the IEEE 754-2008 floating point standard.<p>Impressive! I&#x27;ve understood this to be a hard problem. Unity has promised this for years but still hasn&#x27;t delivered, last time I looked.<p>Is there anywhere we could read more about the tradeoffs and challenges involved?<p>Also, how widely has this been tested?<p>Perhaps most importantly: how can I extend this determinism to my own code?

Do these type of physics engine use Newtonian F=MA at their hearts or do they rely on Lagrangian mechanics?<p>My instinct tells me the first as it seems more straightforward, but then I realized I just have no idea.<p>Anyone knowledgeable care to enlighten?

On a side note, does anyone know what happened to Bullet3D? It seemed like this was a really good candidate for driving game physics a few years ago, but it&#x27;s been rebranded as &quot;PyBullet&quot;, the wiki&#x27;s no longer available, and it seems to have pivoted towards simulation. Also it seems like Bullet3 never got a proper release.<p>Is this a dead project?

They mention wasm bindings. Are there c bindings as well?

Bookmarking this comment section in case I ever need a prime example of bikeshedding.

Regarding inane comments about the name, take a look at this:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Windows_Mobile#Pocket_PC_2000" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Windows_Mobile#Pocket_PC_2000</a><p><i>Pocket PC 2000, originally codenamed &quot;Rapier&quot;, was released on April 19, 2000, and was based on the Windows CE 3.0 kernel.</i>