Tnua - A Character Controller for Bevy.

Tnua ("motion" in Hebrew) is a floating character controller, which means that instead of constantly touching the ground the character floats above it, which makes many aspects of the motion control simpler.

Tnua can use Rapier or XPBD, and supports both the 2D and 3D versions of both with integration crates:

• For Rapier 2D, add the bevy-tnua-rapier2d crate.
• For Rapier 3D, add the bevy-tnua-rapier3d crate.
• For XPBD 2D, add the bevy-tnua-xpbd2d crate.
• For XPBD 3D, add the bevy-tnua-xpbd3d crate.
• Third party integration crates. Such crates should depend on bevy-tnua-physics-integration-layer and not the main bevy-tnua crate.

Note that:

• Both integration crate (bevy-tnua-<physics-backend>) and the main bevy-tnua crate are required, and that the main plugin from both crates should be added.
• If you use a physics backend with double precision (like XPBD with the f64 flag), you need to add the f64 flag to all the Tnua crates. This applies to double precision data that gets defined by the physics backend - Bevy itself will still use single precision, and this is the precision the position and rotation will use.

Features

• Supports both 2D and 3D versions of Rapier and XPBD
• Running
• Jumping
• Crouching
• Variable height jumping
• Coyote time
• Jump buffer
• Running up/down slopes/stairs
• Tilt correction
• Moving platforms
• Rotating platforms
• Animation helpers (not the animation itself, but Tnua has facilities that help deciding which animation to play)
• Jump/fall through platforms
• Air actions

Demos:

• 2D Platformer: Rapier, XPBD, XPBD (f64 version)
• 3D Platformer: Rapier, XPBD, XPBD (f64 version)
• 3D Shooter: Rapier, XPBD, XPBD (f64 version)

The basis and actions in the demos can be tweaked with a GUI. They are initialized to the Default::default() provided in Tnua, with the following exceptions:

• TnuaBuiltinWalk::desired_velocity defaults to the zero vector, but when the user walks the character it is set to a vector of length 20.0 (40.0 in the 2D demo)
• TnuaBuiltinWalk::float_height is set to 2.0 even though it defaults to 0.0. User code should always set the float height based on the model's geometrics.
• TnuaBuiltinWalk::max_slope is set to $\frac{\pi}{4}$ even though it defaults to $\frac{\pi}{2}$ (which disables the slipping behavior, since this is the slope angle of a wall)
• TnuaBuiltinJump::height is set to 4.0 even though it defaults to 0.0. User code should always set the jump height based on the game's requirements (a jump action of zero height is useless)
• TnuaBuiltinCrouch::float_offset is set to -0.9 even though it defaults to 0.0. Just like float_height, this value should always be set by user code based on the model's geometric.
• TnuaBuiltinDash::displacement defaults to 0.0, but when the user inputs the command to dash it gets set to a vector of length 10.0.

Running the Demos Locally

$ cargo run --bin <demo-name> --features <physics-backend>

Where <demo-name> is the name of the demo and <physics-backend> is either rapier2d, rapier3d, xpbd2d or xpbd3d. Make sure to match the dimensionality of the backend (2D or 3D) to that of the demo. For example, to run the 3D platformer with XPBD, use this:

$ cargo run --bin platformer_3d --features xpbd3d

Interesting Parts of the Demo Code

• Check out the demos' entry points to see how the plugins and the player character entities are being set.
• Check out the character control systems to see how to control the character's motion and special movement actions.
• Check out the character animating systems to see how to use information from Tnua for character animation.

Versions

Tnua is broken into different crates that update separately, so this is broken into multiple tables. The version of bevy-tnua-physics-integration-layer must be the same for both the main bevy-tnua crate and the integration crates.

Main

Rapier integration

XPBD integration

Pre-split

Reference Material

The following were used for coding the math and physics of Tnua:

• "Floating capsule" and running mechanics:
  • https://youtu.be/qdskE8PJy6Q
• Jumping mechanics:
  • https://youtu.be/hG9SzQxaCm8
  • https://youtu.be/eeLPL3Y9jjA

Alternatives

• bevy_mod_wanderlust - the original inspiration for this mod, and where I got the floating capsule video from. I ended up creating my own plugin because bevy_mod_wanderlust does not support 2D.
• Rapier itself has a character controller. It's not a floating character controller, but it's integrated with the physics engine itself and uses that privilege to work out some of the problems the floating model is used to address.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

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.