93c17d105a
# Objective - Fixes #12570 ## Solution Previously, cardinal splines constructed by `CubicCardinalSpline` would leave out their endpoints when constructing the cubic curve segments connecting their points. (See the linked issue for details.) Now, cardinal splines include the endpoints. For instance, the provided usage example ```rust let points = [ vec2(-1.0, -20.0), vec2(3.0, 2.0), vec2(5.0, 3.0), vec2(9.0, 8.0), ]; let cardinal = CubicCardinalSpline::new(0.3, points).to_curve(); let positions: Vec<_> = cardinal.iter_positions(100).collect(); ``` will actually produce a spline that connects all four of these points instead of just the middle two "interior" points. Internally, this is achieved by duplicating the endpoints of the vector of control points before performing the construction of the associated `CubicCurve`. This amounts to specifying that the tangents at the endpoints `P_0` and `P_n` (say) should be parallel to `P_1 - P_0` and `P_n - P_{n-1}`. --- ## Migration Guide Any users relying on the old behavior of `CubicCardinalSpline` will have to truncate any parametrizations they used in order to access a curve identical to the one they had previously. This would be done by chopping off a unit-distance segment from each end of the parametrizing interval. For instance, if a user's existing code looks as follows ```rust fn interpolate(t: f32) -> Vec2 { let points = [ vec2(-1.0, -20.0), vec2(3.0, 2.0), vec2(5.0, 3.0), vec2(9.0, 8.0), ]; let my_curve = CubicCardinalSpline::new(0.3, points).to_curve(); my_curve.position(t) } ``` then in order to obtain similar behavior, `t` will need to be shifted up by 1, since the output of `CubicCardinalSpline::to_curve` has introduced a new segment in the interval [0,1], displacing the old segment from [0,1] to [1,2]: ```rust fn interpolate(t: f32) -> Vec2 { let points = [ vec2(-1.0, -20.0), vec2(3.0, 2.0), vec2(5.0, 3.0), vec2(9.0, 8.0), ]; let my_curve = CubicCardinalSpline::new(0.3, points).to_curve(); my_curve.position(t+1) } ``` (Note that this does not provide identical output for values of `t` outside of the interval [0,1].) On the other hand, any user who was specifying additional endpoint tangents simply to get the curve to pass through the right points (i.e. not requiring exactly the same output) can simply omit the endpoints that were being supplied only for control purposes. --- ## Discussion ### Design considerations This is one of the two approaches outlined in #12570 — in this PR, we are basically declaring that the docs are right and the implementation was flawed. One semi-interesting question is how the endpoint tangents actually ought to be defined when we include them, and another option considered was mirroring the control points adjacent to the endpoints instead of duplicating them, which would have had the advantage that the expected length of the corresponding difference should be more similar to that of the other difference-tangents, provided that the points are equally spaced. In this PR, the duplication method (which produces smaller tangents) was chosen for a couple reasons: - It seems to be more standard - It is exceptionally simple to implement - I was a little concerned that the aforementioned alternative would result in some over-extrapolation ### An annoyance If you look at the code, you'll see I was unable to find a satisfactory way of doing this without allocating a new vector. This doesn't seem like a big problem given the context, but it does bother me. In particular, if there is some easy parallel to `slice::windows` for iterators that doesn't pull in an external dependency, I would love to know about it. |
||
|---|---|---|
| .cargo | ||
| .github | ||
| assets | ||
| benches | ||
| crates | ||
| docs | ||
| docs-template | ||
| errors | ||
| examples | ||
| src | ||
| tests | ||
| tools | ||
| .gitattributes | ||
| .gitignore | ||
| Cargo.toml | ||
| CHANGELOG.md | ||
| clippy.toml | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| CREDITS.md | ||
| deny.toml | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| README.md | ||
| rustfmt.toml | ||
| typos.toml | ||
What is Bevy?
Bevy is a refreshingly simple data-driven game engine built in Rust. It is free and open-source forever!
WARNING
Bevy is still in the early stages of development. Important features are missing. Documentation is sparse. A new version of Bevy containing breaking changes to the API is released approximately once every 3 months. We provide migration guides, but we can't guarantee migrations will always be easy. Use only if you are willing to work in this environment.
MSRV: Bevy relies heavily on improvements in the Rust language and compiler. As a result, the Minimum Supported Rust Version (MSRV) is generally close to "the latest stable release" of Rust.
Design Goals
- Capable: Offer a complete 2D and 3D feature set
- Simple: Easy for newbies to pick up, but infinitely flexible for power users
- Data Focused: Data-oriented architecture using the Entity Component System paradigm
- Modular: Use only what you need. Replace what you don't like
- Fast: App logic should run quickly, and when possible, in parallel
- Productive: Changes should compile quickly ... waiting isn't fun
About
- Features: A quick overview of Bevy's features.
- News: A development blog that covers our progress, plans and shiny new features.
Docs
- Quick Start Guide: Bevy's official Quick Start Guide. The best place to start learning Bevy.
- Bevy Rust API Docs: Bevy's Rust API docs, which are automatically generated from the doc comments in this repo.
- Official Examples: Bevy's dedicated, runnable examples, which are great for digging into specific concepts.
- Community-Made Learning Resources: More tutorials, documentation, and examples made by the Bevy community.
Community
Before contributing or participating in discussions with the community, you should familiarize yourself with our Code of Conduct.
- Discord: Bevy's official discord server.
- Reddit: Bevy's official subreddit.
- GitHub Discussions: The best place for questions about Bevy, answered right here!
- Bevy Assets: A collection of awesome Bevy projects, tools, plugins and learning materials.
Contributing
If you'd like to help build Bevy, check out the Contributor's Guide. For simple problems, feel free to open an issue or PR and tackle it yourself!
For more complex architecture decisions and experimental mad science, please open an RFC (Request For Comments) so we can brainstorm together effectively!
Getting Started
We recommend checking out the Quick Start Guide for a brief introduction.
Follow the Setup guide to ensure your development environment is set up correctly. Once set up, you can quickly try out the examples by cloning this repo and running the following commands:
# Switch to the correct version (latest release, default is main development branch)
git checkout latest
# Runs the "breakout" example
cargo run --example breakout
To draw a window with standard functionality enabled, use:
use bevy::prelude::*;
fn main(){
App::new()
.add_plugins(DefaultPlugins)
.run();
}
Fast Compiles
Bevy can be built just fine using default configuration on stable Rust. However for really fast iterative compiles, you should enable the "fast compiles" setup by following the instructions here.
Bevy Cargo Features
This list outlines the different cargo features supported by Bevy. These allow you to customize the Bevy feature set for your use-case.
Thanks
Bevy is the result of the hard work of many people. A huge thanks to all Bevy contributors, the many open source projects that have come before us, the Rust gamedev ecosystem, and the many libraries we build on.
A huge thanks to Bevy's generous sponsors. Bevy will always be free and open source, but it isn't free to make. Please consider sponsoring our work if you like what we're building.
This project is tested with BrowserStack.
License
Bevy is free, open source and permissively licensed! Except where noted (below and/or in individual files), all code in this repository is dual-licensed under either:
- MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
at your option. This means you can select the license you prefer! This dual-licensing approach is the de-facto standard in the Rust ecosystem and there are very good reasons to include both.
Some of the engine's code carries additional copyright notices and license terms due to their external origins.
These are generally BSD-like, but exact details vary by crate:
If the README of a crate contains a 'License' header (or similar), the additional copyright notices and license terms applicable to that crate will be listed.
The above licensing requirement still applies to contributions to those crates, and sections of those crates will carry those license terms.
The license field of each crate will also reflect this.
For example, bevy_mikktspace has code under the Zlib license (as well as a copyright notice when choosing the MIT license).
The assets included in this repository (for our examples) typically fall under different open licenses. These will not be included in your game (unless copied in by you), and they are not distributed in the published bevy crates. See CREDITS.md for the details of the licenses of those files.
Your contributions
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.