Ammo Physics (3D Physics Extension)

[Brackets-Coder]

Ammo Physics

A work-in-progress extension based on the ammo.js physics library, which is based on the C++ Bullet Physics SDK.

The goal is to provide feature-complete, advanced, and performant 3D physics in a simple-to-understand manner. This extension aims to be consistent with Box2D and Simple3D.

video.mp4

Task list:

• Shapes
  • Boxes
  • Spheres
  • Cylinders
  • Cones
  • Capsules
  • Convex Hulls
  • Triangle Meshes
  • Compound bodies
  • There are some others (planes, heightfields), but I don't want to support these
• Physical Materials (friction, restitution, etc.)
• Constraints (All types)
• Collision:
  • Collision Detection
  • Raycasting
  • Enable/disable collision response
• Manual Impact forces (like "push with force" block in Box2D)
• Bug fixing

Things I'm considering now or for a later update:

• Vehicle support
• Debug rendering support
• Soft Bodies

Miscellaneous Notes Mainly for Moderators:

• ChatGPT was used to assist and enhance the making of this extension, simply because I couldn't find good quality, coherent documentation of Ammo.js, and attempting to figure out how to use it via the developer inspector isn't fun. It did not write the code for me and I am still the main author of this extension. It just helped me learn Ammo.js. Hope this doesn't cause conflicts.
• I'm not good at graphic design so if someone wants to make a banner/thumbnail that'd be great
• Still have to incorporate Scratch.Cast where necessary, right now I'm just working on functionality though

Put an emoji (👍, 🚀) if you like this extension

[WAYLIVES]

Wow! It's very cool and useful for people like me)

[Brackets-Coder]

Wow! It's very cool and useful for people like me)

Thank you! I've been making steady progress, but it probably won't be ready for a while (which is why this is a draft).

[Brackets-Coder]

Added partial support compound bodies - all child shape types.
Also working on convex and concave mesh support... it'll be a while.

[WAYLIVES]

wow

[Brackets-Coder]

Finally got convex hulls working 🥳 🎉

video.mp4

Still have to optimize and bug fix everything and add more features

[Xeltalliv]

It's a bit complicated. Simple3D itself can have meshes represented in 3 ways: triangles, triangle strips and triangle fans. Positions of each of the vertices can either be listed directly, or be specified once per unique position and referenced multiple times from the list of indices, to share one vertex between multiple primitives. Triangles require 3 vertices per triangle. Triangle strips and fans require 3 vertices for the first triangle and only 1 vertex for each subsequent triangle, where 2 old vertices get reused. In case of triangle strip it reused 2 immediately previous vertices. In case of triangle fan it reuses 1 previous vertex and the 1st vertex. Index of 0 can be used as a separator to have multiple unconnected triangle strips/fans.

The built-in OBJ importer doesn't use any of those modes and always just outputs a simple list of triangles pre-processed using fan triangulation algorithm. It does not handle concave n-gons.

[Brackets-Coder]

Also, Ammo.js seems to support wireframe debug rendering. I might want to add a layer to the canvas that can show contacts, convex hulls, velocities, etc.

[Xeltalliv]

This looks like a faulty collision detection. Changing framerate, sub-steps and solver iterations is mostly useful when you have a lot of bodies interacting in a chain reaction, which isn't the case here.

I could try using a more specialized collision algorithm but I don't want to sacrifice performance for simpler simulations.

Not sure exactly what you are referring to, because there isn't much documentation, but I asked ChatGPT how to correctly use btGImpactMeshShape and it on it's own mentioned that using btGImpactCollisionAlgorithm is absolutely mandatory for it to work correctly.

[Brackets-Coder]

This looks like a faulty collision detection. Changing framerate, sub-steps and solver iterations is mostly useful when you have a lot of bodies interacting in a chain reaction, which isn't the case here.

I could try using a more specialized collision algorithm but I don't want to sacrifice performance for simpler simulations.

Not sure exactly what you are referring to, because there isn't much documentation, but I asked ChatGPT how to correctly use btGImpactMeshShape and it on it's own mentioned that using btGImpactCollisionAlgorithm::registerAlgorithm is absolutely mandatory for it to work correctly.

I'm already registering the GImpactCollisionAlgorithm, but ChatGPT suggests using a more narrow phase parent collision algorithm... I don't really think that will affect anything. Looking at the official demos, btDbvtBroadphase is being used and that's what I'm using. I could try to see if I'm registering the impact collision algorithm correctly, but I think I am:

    let dispatcher = new Ammo.btCollisionDispatcher(collisionConfig);
    Ammo.btGImpactCollisionAlgorithm.prototype.registerAlgorithm(dispatcher);

[Brackets-Coder]

there's no freaking documentation writing constraints is a pain 😞

[Brackets-Coder]

@CubesterYT I'm pretty sure this isn't possible but the best ammo.js projects use WebAssembly / Web workers to let the physics run async in the background so it doesn't hinder rendering processes, etc, also have more memory capacity.

I'm assuming this isn't possible in TW and it has to be native JS?

[Brackets-Coder]

@wiktorlaskowski and @WAYLIVES might want to take a look at the placeholder banner and see if it's acceptable

[Kreerio]

woah thats awsome

[Brackets-Coder]

woah thats awsome

What the banner?

[Brackets-Coder]

@GarboMuffin and/or @CubesterYT

I'd like this extension to be able to support WebAssembly as it has much higher performance and much lower memory limitations.
The way I've set it up now is that a ammo.wasm.wasm file would be hosted at extensions.turbowarp.org/MasterMath/ammo.wasm.wasm

The extension would check if that file exists, if so load the WASM ammo with it, if not fall back to the default offline native JS version (at the cost of performance). This way there's no external domains and the extension should always load with some kind of Ammo.

In practice, it looks like this:

would something like this even work?

[GarboMuffin]

I'll just be real with you. The likelihood that I would tolerate merging a 2MB extension is really low right now

[Brackets-Coder]

Alternatively, I could build my own version of Ammo without the extra stuff that is much smaller than the prebuilt library, but it would probably remove things like the wireframe debug drawer which might be nice (but a lot of work and size) to implement later...

[Brackets-Coder]

Alternatively, I could build my own version of Ammo without the extra stuff that is much smaller than the prebuilt library, but it would probably remove things like the wireframe debug drawer which might be nice (but a lot of work and size) to implement later...

I could probably half the file size if I did that though

[Brackets-Coder]

@GarboMuffin

Hello Mr. Weber,
I made a custom build of Ammo.js with soft bodies and debug drawing disabled. I've also enabled WebAssembly and embedded it directly into the JS file, so I don't need to access extra files on the server, which probably wouldn't work anyway. I also configured the build to default at 128 MB memory limit and dynamically increase if needed. Terser minified and compressed it.

This makes it run faster, have "infinite" memory limitations (can be both good or bad, but it fixes the crashing Out of Memory issue), and the entire extension size is now only 1.2 MB (with all the blocks and stuff too). Is that good with you or should I compress further? What is the preferred size? I could probably get it a few hundred kilobytes, but that would be more aggressive and I don't think I can go further than that.

[Brackets-Coder]

!format

[github-actions]

The formatting bot didn't find any formatting issues. It currently only checks the extensions folder. The author or a maintainer can run terminal command 'npm run format' manually to format all files.

[Brackets-Coder]

@CubesterYT since the last commit where I made a custom build of the library, format is failing even though npm run check-format passed on my local machine. Why is that?

[GarboMuffin]

it's because of the prettier update pull request you merged where now your local prettier doesn't match what's on your pull request branch

that's why the pull request wasn't merged for a long time

rebase, reinstall, reformat, itll go away

[GarboMuffin]

!format

prettier updates are now blocked from dependabot so that mistake won't be possible to make again

[github-actions]

The formatting bot didn't find any formatting issues. It currently only checks the extensions folder. The author or a maintainer can run terminal command 'npm run format' manually to format all files.

[Brackets-Coder]

it's because of the prettier update pull request you merged where now your local prettier doesn't match what's on your pull request branch

that's why the pull request wasn't merged for a long time

rebase, reinstall, reformat, itll go away

Oops sorry just trying to help

[Daniel-Dami]

this extension is super cool!!

[Brackets-Coder]

this extension is super cool!!

Thanks! Apparently though, it's too large, so I'll have to find some way to compress the library further

[Brackets-Coder]

Previous commit reduces the file size ≈0.2 MB
The extension is now only 1MB (1020 KB, around half the original size); I don't think I can do much better than that without breaking functionality.