I saw this thread on reddit and decided to give the crate a try. Unfortunately it does not compile on recent nightlies (I tried with one from three days ago and today).

error[E0277]: the trait bound `*mut std::ops::FnMut(glium::<unnamed>::Event) + 'static: std::marker::Send` is not satisfied in `std::option::Option<*mut std::ops::FnMut(glium::<unnamed>::Event) + 'static>`
   --> src/universe/mod.rs:316:23
    |
316 |                 scope.execute(move || {
    |                       ^^^^^^^ `*mut std::ops::FnMut(glium::<unnamed>::Event) + 'static` cannot be sent between threads safely
    |
    = help: within `std::option::Option<*mut std::ops::FnMut(glium::<unnamed>::Event) + 'static>`, the trait `std::marker::Send` is not implemented for `*mut std::ops::FnMut(glium::<unnamed>::Event) + 'static`
    = note: required because it appears within the type `std::option::Option<*mut std::ops::FnMut(glium::<unnamed>::Event) + 'static>`
    = note: required because of the requirements on the impl of `std::marker::Send` for `std::sync::Mutex<std::option::Option<*mut std::ops::FnMut(glium::<unnamed>::Event) + 'static>>`
    = note: required because it appears within the type `winit::platform::platform::events_loop::UserCallback`
    = note: required because it appears within the type `winit::platform::platform::events_loop::Shared`
    = note: required because of the requirements on the impl of `std::marker::Send` for `std::sync::Arc<winit::platform::platform::events_loop::Shared>`
    = note: required because it appears within the type `winit::platform::platform::events_loop::EventsLoop`
    = note: required because it appears within the type `glium::<unnamed>::EventsLoop`
    = note: required because of the requirements on the impl of `std::marker::Send` for `std::sync::Mutex<glium::<unnamed>::EventsLoop>`
    = note: required because of the requirements on the impl of `std::marker::Sync` for `std::sync::Arc<std::sync::Mutex<glium::<unnamed>::EventsLoop>>`
    = note: required because it appears within the type `std::option::Option<std::sync::Arc<std::sync::Mutex<glium::<unnamed>::EventsLoop>>>`
    = note: required because it appears within the type `simulation::SimulationContext`
    = note: required because of the requirements on the impl of `std::marker::Send` for `&simulation::SimulationContext`
    = note: required because it appears within the type `[closure@src/universe/mod.rs:316:31: 345:18 index:usize, buffer_width:u32, context:&simulation::SimulationContext, buffer_width_half:u32, buffer_height_half:u32, self:&Self, time:&std::time::Duration, max_depth:u32, buffer_height:u32, chunk:&mut [u8]]`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
error: Could not compile `euclider`.

It's kind of unwieldy having to write all the deserializers manually in one place. Maybe make macros that create the deserializers automatically? Mainly, it the deserializers shouldn't all be declared in the scene.rs file, but rather in files the struct resides in. If a good solution is found, maybe I could even externalize the code into a crate library.

I have changed the Cargo.toml file to

[package]
edition = "2021"

after running

cargo build --release

only a few errors occur:

error[E0432]: unresolved import `winapi::shared::winerror`
  --> C:\Users\XX\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.16.2\src\platform\windows\dpi.rs:15:21
   |
15 | use winapi::shared::winerror::S_OK;
   |                     ^^^^^^^^ could not find `winerror` in `shared`

error[E0432]: unresolved import `winapi::um::errhandlingapi`
 --> C:\Users\XX\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.16.2\src\platform\windows\util.rs:7:17
  |
7 | use winapi::um::errhandlingapi::GetLastError;
  |                 ^^^^^^^^^^^^^^ could not find `errhandlingapi` in `um`

error[E0432]: unresolved import `winapi::shared::winerror`
    --> C:\Users\XX\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.16.2\src\platform\windows\window.rs:1153:33
     |
1153 |             use winapi::shared::winerror::S_OK;
     |                                 ^^^^^^^^ could not find `winerror` in `shared`

For more information about this error, try `rustc --explain E0432`.
error: could not compile `winit` due to 3 previous errors
warning: build failed, waiting for other jobs to finish...

Output of

rustc --explain E0432

An import was unresolved.

Erroneous code example:

use something::Foo; // error: unresolved import `something::Foo`.

In Rust 2015, paths in `use` statements are relative to the crate root. To
import items relative to the current and parent modules, use the `self::` and
`super::` prefixes, respectively.

In Rust 2018 or later, paths in `use` statements are relative to the current
module unless they begin with the name of a crate or a literal `crate::`, in
which case they start from the crate root. As in Rust 2015 code, the `self::`
and `super::` prefixes refer to the current and parent modules respectively.

Also verify that you didn't misspell the import name and that the import exists
in the module from where you tried to import it. Example:

use self::something::Foo; // Ok.

mod something {
    pub struct Foo;
}

If you tried to use a module from an external crate and are using Rust 2015,
you may have missed the `extern crate` declaration (which is usually placed in
the crate root):

extern crate core; // Required to use the `core` crate in Rust 2015.

use core::any;

Since Rust 2018 the `extern crate` declaration is not required and
you can instead just `use` it:

use core::any; // No extern crate required in Rust 2018.

Reproduce:

• Have latest rustup installed with the nightly toolchain.
• Clone the repo
• cagro +nightly run --release
• 35 errors found, mostly missing macros.
• 1000+ warnings found, mostly deprecated conventions e.g. the try! macro.

GeneralIntersector returns a Boxed type. Since these functions can be called several thousand times per frame, it may be worth considering an alternative that doesn't require heap allocation.

https://github.com/Limeth/euclider/blob/master/src/universe/entity/shape.rs#L35-L40