avian3d/dynamics/ccd/mod.rs
1//! Contains components and functionality for Continuous Collision Detection.
2//!
3//! # What Is CCD?
4//!
5//! Physics simulation is typically done in a discrete manner.
6//! At the beginning of each physics frame, the simulation checks for collisions,
7//! and if none are found for a given rigid body, it is free to move according to
8//! its velocity and the size of the timestep.
9//!
10//! This generally works well for large or slowly moving objects, but fast and small
11//! objects can pass through thin geometry such as walls and triangle meshes.
12//! This phenomenon is often called **tunneling**.
13//!
14//! <svg width="300" height="350" viewBox="0 0 300 350" fill="none" xmlns="http://www.w3.org/2000/svg">
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19//! <text x="150" y="325" style="fill: #b4b4b4; font: 18px monospace; text-anchor: middle;">Discrete</text>
20//! </svg>
21//!
22//! **Continuous Collision Detection** (CCD) aims to prevent tunneling.
23//! Currently, two approaches are supported: [Speculative Collision](#speculative-collision) and [Swept CCD](#swept-ccd).
24//! Speculative collision is enabled by default, but swept CCD is opt-in with the [`SweptCcd`] component.
25//! The two approaches can also be used together.
26//!
27//! ## Speculative Collision
28//!
29//! **Speculative collision** is a form of Continuous Collision Detection
30//! where contacts are predicted before they happen. The contacts are only
31//! solved if the entities are expected to come into contact within the next frame.
32//!
33//! To determine whether two bodies may come into contact, their [AABBs](ColliderAabb) are expanded
34//! based on their velocities. Additionally, a **speculative margin** is used to determine
35//! the maximum distance at which a collision pair can generate speculative contacts.
36//!
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48//! <text x="184" y="125" style="fill: #db9010; font: 16px monospace; text-anchor: middle;">Collision AABB</text>
49//! <text x="160" y="40" style="fill: #eb4a5a; font: 16px monospace; text-anchor: middle;">Speculative Margin</text>
50//! <text x="210" y="340" style="fill: #b4b4b4; font: 16px monospace; text-anchor: start;">Unconstrained</text>
51//! <text x="210" y="205" style="fill: #b4b4b4; font: 16px monospace; text-anchor: start;">Constrained</text>
52//! <text y="240" style="fill: #a874d8; font: 16px monospace; font-weight: bold; text-anchor: end;">
53//! <tspan x="155">Speculative</tspan><tspan x="155" dy="18">Contact</tspan>
54//! </text>
55//! </svg>
56//!
57//! The current "effective" speculative margin for a body is determined by its velocity
58//! clamped by the specified maximum bound. By default, the maximum bound is infinite,
59//! but it can be configured for all entities using the [`NarrowPhaseConfig`] resource,
60//! and for individual entities using the [`SpeculativeMargin`] component.
61//!
62//! ```
63#![cfg_attr(feature = "2d", doc = "use avian2d::prelude::*;")]
64#![cfg_attr(feature = "3d", doc = "use avian3d::prelude::*;")]
65//! use bevy::prelude::*;
66//!
67//! fn setup(mut commands: Commands) {
68//! // Spawn a rigid body with a maximum bound for the speculative margin.
69//! commands.spawn((
70//! RigidBody::Dynamic,
71//! Collider::capsule(0.5, 2.0),
72//! SpeculativeMargin(2.0),
73//! ));
74//! }
75//! ```
76//!
77//! Speculative collisions are an efficient and generally robust approach
78//! to Continuous Collision Detection. They are enabled for all bodies by default,
79//! provided that the default naximum speculative margin is greater than zero.
80//!
81//! However, speculative collisions aren't entirely without issues,
82//! and there are some cases where large speculative margins can cause undesired behavior.
83//!
84//! ### Caveats of Speculative Collision
85//!
86//! Speculative contacts are approximations. They typically have good enough accuracy,
87//! but when bodies are moving past each other at high speeds, the prediction can sometimes
88//! fail and lead to **ghost collisions**. This happens because contact surfaces are treated
89//! like infinite planes from the point of view of the solver. Ghost collisions typically manifest
90//! as objects bumping into seemingly invisible walls.
91//!
92//! <svg width="475" height="400" viewBox="0 0 475 400" fill="none" xmlns="http://www.w3.org/2000/svg">
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100//! <path d="M160 160V265" stroke="#a874d8" stroke-width="2" stroke-dasharray="5 5"/>
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103//! <line x1="160" y1="264" x2="400" y2="264" stroke="#a874d8" stroke-width="2" stroke-dasharray="6 6"/>
104//! <text x="184" y="125" style="fill: #db9010; font: 16px monospace; text-anchor: middle;">Collision AABB</text>
105//! <text x="160" y="40" style="fill: #eb4a5a; font: 16px monospace; text-anchor: middle;">Speculative Margin</text>
106//! <text x="345" y="340" style="fill: #b4b4b4; font: 16px monospace; text-anchor: start;">Unconstrained</text>
107//! <text x="345" y="205" style="fill: #b4b4b4; font: 16px monospace; text-anchor: start;">Constrained</text>
108//! <text x="190" y="280" style="fill: #a874d8; font: 16px monospace; font-weight: bold; text-anchor: start;">Ghost Collision Plane</text>
109//! </svg>
110//!
111//! Ghost collisions can be mitigated by using a smaller [`SpeculativeMargin`]
112//! or a higher [`Physics`] timestep rate.
113//!
114//! Another caveat of speculative collisions is that they can still occasionally miss contacts,
115//! especially for thin objects spinning at very high speeds. This is typically quite rare however,
116//! and speculative collision should work fine for the majority of cases.
117//!
118//! Speculative collisions can also absorb some energy in contacts, causing even perfectly elastic
119//! objects to lose kinetic energy over several bounces.
120//!
121//! For an approach that is more expensive but doesn't suffer from ghost collisions,
122//! missed collisions, or inaccurate restitution, consider using swept CCD,
123//! which is described in the following section.
124//!
125//! ## Swept CCD
126//!
127//! *Note: Swept CCD currently only supports the built-in `Collider`.*
128//!
129//! **Swept CCD** is a form of Continuous Collision Detection that sweeps potentially colliding objects
130//! from their previous positions to their current positions, and if a collision is found, moves the bodies
131//! back to the time of impact. This way, the normal collision algorithms will be able to detect and handle
132//! the collision during the next frame.
133//!
134//! There are two variants of swept CCD: [`Linear`](SweepMode::Linear)
135//! and [`NonLinear`](SweepMode::Linear). The difference between the two
136//! is that [`Linear`](SweepMode::Linear) only considers translational motion,
137//! so bodies can still pass through objects that are spinning at high speeds,
138//! while [`NonLinear`](SweepMode::NonLinear) also considers rotational motion,
139//! but is more expensive.
140//!
141//! <svg width="300" height="350" viewBox="0 0 300 350" fill="none" xmlns="http://www.w3.org/2000/svg">
142//! <rect x="141" y="1" width="18" height="298" fill="#64C850" stroke="black" stroke-width="2"/>
143//! <circle cx="115" cy="150" r="24" stroke="#5064C8" stroke-width="2" stroke-dasharray="4 4"/>
144//! <circle cx="25" cy="150" r="24" fill="#5064C8" stroke="black" stroke-width="2"/>
145//! <path d="M115.707 150.707C116.098 150.317 116.098 149.683 115.707 149.293L109.343 142.929C108.953 142.538 108.319 142.538 107.929 142.929C107.538 143.319 107.538 143.953 107.929 144.343L113.586 150L107.929 155.657C107.538 156.047 107.538 156.681 107.929 157.071C108.319 157.462 108.953 157.462 109.343 157.071L115.707 150.707ZM25 151H115V149H25V151Z" fill="#E19664"/>
146//! <text x="150" y="325" style="fill: #b4b4b4; font: 18px monospace; text-anchor: middle;">Linear / NonLinear</text>
147//! </svg>
148//!
149//! <svg width="600" height="350" viewBox="0 0 600 350" fill="none" xmlns="http://www.w3.org/2000/svg">
150//! <rect x="438.95" y="25.3488" width="18" height="298" transform="rotate(27.5 438.95 25.3488)" stroke="#64C850" stroke-width="2" stroke-dasharray="4 4"/>
151//! <rect x="301" y="1" width="18" height="298" fill="#64C850" stroke="black" stroke-width="2"/>
152//! <circle cx="425" cy="150" r="24" fill="#5064C8" stroke="black" stroke-width="2"/>
153//! <text x="150" y="325" style="fill: #b4b4b4; font: 18px monospace; text-anchor: middle;">Linear</text>
154//! <circle cx="310" cy="290" r="5" fill="#D9D9D9" stroke="black" stroke-width="2"/>
155//! <path d="M322.96 148.816L323.331 149.745L323.331 149.745L322.96 148.816ZM361.786 156.786L361.078 157.493L361.078 157.493L361.786 156.786ZM365 161C365.552 161 366 160.552 366 160L366 151C366 150.448 365.552 150 365 150C364.448 150 364 150.448 364 151L364 159L356 159C355.448 159 355 159.448 355 160C355 160.552 355.448 161 356 161L365 161ZM320.371 150.928L323.331 149.745L322.588 147.888L319.629 149.072L320.371 150.928ZM361.078 157.493L364.293 160.707L365.707 159.293L362.493 156.078L361.078 157.493ZM323.331 149.745C336.331 144.545 351.178 147.592 361.078 157.493L362.493 156.078C352.027 145.612 336.331 142.391 322.588 147.888L323.331 149.745Z" fill="#E19664"/>
156//! <rect x="259.442" y="133.366" width="18" height="298" transform="rotate(60 259.442 133.366)" stroke="#64C850" stroke-width="2" stroke-dasharray="4 4"/>
157//! <rect x="1" y="1" width="18" height="298" fill="#64C850" stroke="black" stroke-width="2"/>
158//! <circle cx="125" cy="150" r="24" fill="#5064C8" stroke="black" stroke-width="2"/>
159//! <text x="450" y="325" style="fill: #b4b4b4; font: 18px monospace; text-anchor: middle;">NonLinear</text>
160//! <circle cx="10" cy="290" r="5" fill="#D9D9D9" stroke="black" stroke-width="2"/>
161//! <path d="M54.0561 245.357L53.1144 245.694L53.1144 245.694L54.0561 245.357ZM54.5719 248.904C55.071 249.14 55.6673 248.927 55.9037 248.428L59.7565 240.294C59.9929 239.795 59.7799 239.199 59.2808 238.963C58.7817 238.726 58.1854 238.939 57.949 239.438L54.5243 246.668L47.2944 243.243C46.7953 243.007 46.199 243.22 45.9626 243.719C45.7261 244.218 45.9391 244.815 46.4382 245.051L54.5719 248.904ZM53.1144 245.694L54.0582 248.336L55.9417 247.664L54.9978 245.021L53.1144 245.694ZM20.3714 230.928C33.4979 225.678 48.3594 232.379 53.1144 245.694L54.9978 245.021C49.8615 230.639 33.808 223.4 19.6286 229.071L20.3714 230.928Z" fill="#E19664"/>
162//! </svg>
163//!
164//! To enable swept CCD for a rigid body, simply add the [`SweptCcd`] component
165//! and make sure that the [`CcdPlugin`] is enabled. The plugin is included
166//! in the [`PhysicsPlugins`] plugin group.
167//!
168//! ```
169#![cfg_attr(feature = "2d", doc = "use avian2d::prelude::*;")]
170#![cfg_attr(feature = "3d", doc = "use avian3d::prelude::*;")]
171//! use bevy::prelude::*;
172//!
173//! fn setup(mut commands: Commands) {
174//! // Spawn a rigid body with swept CCD enabled.
175//! // `SweepMode::NonLinear` is used by default.
176//! commands.spawn((
177//! RigidBody::Dynamic,
178//! Collider::capsule(0.5, 2.0),
179//! SweptCcd::default(),
180//! ));
181//! }
182//! ```
183//!
184//! See the [documentation](SweptCcd) of the component for more details
185//! and configuration options.
186//!
187//! Swept CCD is more expensive than [Speculative Collision](#speculative-collision),
188//! but it doesn't have the same issues with ghost collisions or missed collisions.
189//! It is primarily intended as a safety net when it is crucial that a body never
190//! tunnels through geometry. Swept CCD should only be used when necessary,
191//! as it also has its own set of problems.
192//!
193//! ### Caveats of Swept CCD
194//!
195//! The [`Linear`](SweepMode::Linear) and [`NonLinear`](SweepMode::Linear)
196//! approaches can lead to *time loss* or *time stealing*, where bodies appear to momentarily
197//! move slower when Swept CCD is active. This happens because they are essentially moved
198//! backwards in time to avoid missing the collision.
199//!
200//! Swept CCD might also not account for chain reactions properly, so if a fast-moving body
201//! bumps into another body, making it a fast-moving body that potentially bumps into
202//! even more bodies, the collisions might not propagate accurately.
203//! However, speculative contacts do detect secondary collisions quite well,
204//! so using the two together can help mitigate the issue.
205//!
206//! Time loss and chain reactions could also be better accounted for with a substepped
207//! time-of-impact solver, but that would be much more expensive and complex,
208//! so it is not yet supported.
209//!
210//! ## Other Ways to Avoid Tunneling
211//!
212//! CCD is one way to prevent objects from tunneling through each other,
213//! but it should only be used when necessary. There are several other approaches
214//! worth considering to help avoid the issue.
215//!
216//! The most obvious way is to simply avoid small or thin geometry such as triangle meshes,
217//! and to make colliders for objects like walls slightly thicker than necessary.
218//! This is of course typically not possible everywhere, but it is good to keep in mind
219//! when authoring levels.
220//!
221//! Triangle mesh colliders are especially prone to tunneling for dynamic rigid bodies.
222//! For shapes that are intended to be solid from the inside, it is recommended
223//! to use convex decomposition instead.
224//!
225//! If you must use triangle mesh colliders and are having stability issues, consider
226//! giving them a small amount of extra thickness using the [`CollisionMargin`] component.
227//! This helps prevent objects from passing through the surface while also reducing
228//! numerical errors and improving performance.
229//!
230//! Finally, making the [physics timestep](Physics) smaller can also help.
231//! However, this comes at the cost of worse performance for the entire simulation.
232
233use crate::prelude::*;
234#[cfg(any(feature = "parry-f32", feature = "parry-f64"))]
235use bevy::ecs::query::QueryData;
236use bevy::prelude::*;
237use derive_more::From;
238#[cfg(any(feature = "parry-f32", feature = "parry-f64"))]
239use dynamics::solver::SolverDiagnostics;
240#[cfg(any(feature = "parry-f32", feature = "parry-f64"))]
241use parry::query::{
242 cast_shapes, cast_shapes_nonlinear, NonlinearRigidMotion, ShapeCastHit, ShapeCastOptions,
243};
244
245/// A plugin for [Continuous Collision Detection](self).
246pub struct CcdPlugin;
247
248impl Plugin for CcdPlugin {
249 fn build(&self, app: &mut App) {
250 app.register_type::<SweptCcd>().register_type::<SweepMode>();
251
252 // Get the `PhysicsSchedule`, and panic if it doesn't exist.
253 let physics = app
254 .get_schedule_mut(PhysicsSchedule)
255 .expect("add PhysicsSchedule first");
256
257 physics.configure_sets(SweptCcdSet.in_set(SolverSet::PostSubstep));
258
259 #[cfg(any(feature = "parry-f32", feature = "parry-f64"))]
260 physics.add_systems(solve_swept_ccd.in_set(SweptCcdSet));
261 }
262}
263
264/// A system set for [Continuous Collision Detection](self) systems.
265#[derive(SystemSet, Clone, Copy, Debug, PartialEq, Eq, Hash)]
266pub struct SweptCcdSet;
267
268/// The maximum distance at which [speculative contacts](self#speculative-collision)
269/// are generated for this entity. A value greater than zero helps prevent missing
270/// contacts for moderately fast-moving and thin objects.
271///
272/// In general, this component should not be needed. The default speculative margin
273/// for all objects is defined in the [`NarrowPhaseConfig`] resource, and it is unbounded
274/// by default, meaning that the margin can extend infinitely. The margin can be bounded
275/// for individual entities using this component in case speculative contacts are causing
276/// issues like the ones outlined [here](self#caveats-of-speculative-collision).
277///
278/// See the [module-level documentation](self) for information about
279/// Speculative Conllision and Continuous Collision Detection in general.
280///
281/// # Example
282///
283/// ```
284#[cfg_attr(feature = "2d", doc = "use avian2d::prelude::*;")]
285#[cfg_attr(feature = "3d", doc = "use avian3d::prelude::*;")]
286/// use bevy::prelude::*;
287///
288/// fn setup(mut commands: Commands) {
289/// // Spawn a rigid body with an unbounded speculative margin.
290/// commands.spawn((
291/// RigidBody::Dynamic,
292/// Collider::capsule(0.5, 2.0),
293/// SpeculativeMargin::MAX,
294/// ));
295/// }
296/// ```
297#[derive(Component, Clone, Copy, Debug, Deref, DerefMut, PartialEq, Reflect, From)]
298#[reflect(Component)]
299#[doc(alias = "SweptCcdPredictionDistance")]
300pub struct SpeculativeMargin(pub Scalar);
301
302impl SpeculativeMargin {
303 /// A zero speculative margin. Disables speculative collision for this entity.
304 pub const ZERO: Self = Self(0.0);
305
306 /// An unbounded speculative margin.
307 pub const MAX: Self = Self(Scalar::MAX);
308}
309
310/// A component that enables sweep-based [Continuous Collision Detection](self) (CCD)
311/// for a [`RigidBody`]. This helps prevent missed collisions for small and fast-moving objects.
312///
313/// By default, swept CCD considers both translational and rotational motion, and is used
314/// against all types of rigid bodies and colliders. This behavior can be modified
315/// by changing [`SweptCcd::mode`] and other properties.
316///
317/// CCD is generally not useful for large or slow objects, as they are less likely
318/// to miss collisions. It is recommended to only use swept CCD when necessary,
319/// as it is more expensive than [speculative collision](self#speculative-collision) and discrete collision detection.
320///
321/// Read the [module-level documentation](self) for more information about what CCD is,
322/// what it is used for, and what limitations and tradeoffs it can have.
323///
324/// # Example
325///
326/// ```
327#[cfg_attr(feature = "2d", doc = "use avian2d::prelude::*;")]
328#[cfg_attr(feature = "3d", doc = "use avian3d::prelude::*;")]
329/// use bevy::prelude::*;
330///
331/// # #[cfg(feature = "f32")]
332/// fn setup(mut commands: Commands) {
333/// // Spawn a dynamic rigid body with swept CCD, travelling towards the right at a high speed.
334/// // The default CCD configuration considers both translational and rotational motion.
335/// commands.spawn((
336/// RigidBody::Dynamic,
337/// SweptCcd::default(),
338#[cfg_attr(feature = "2d", doc = " LinearVelocity(Vec2::X * 100.0),")]
339#[cfg_attr(feature = "3d", doc = " LinearVelocity(Vec3::X * 100.0),")]
340#[cfg_attr(feature = "2d", doc = " Collider::circle(0.1),")]
341#[cfg_attr(feature = "3d", doc = " Collider::sphere(0.1),")]
342/// Transform::from_xyz(-10.0, 3.0, 0.0),
343/// ));
344///
345/// // Spawn another dynamic rigid body with swept CCD, but this time only considering
346/// // linear motion and not rotation.
347/// commands.spawn((
348/// RigidBody::Dynamic,
349/// SweptCcd::LINEAR, // or `SweptCcd::new_with_mode(SweepMode::Linear)`
350#[cfg_attr(feature = "2d", doc = " LinearVelocity(Vec2::X * 100.0),")]
351#[cfg_attr(feature = "3d", doc = " LinearVelocity(Vec3::X * 100.0),")]
352#[cfg_attr(feature = "2d", doc = " Collider::circle(0.1),")]
353#[cfg_attr(feature = "3d", doc = " Collider::sphere(0.1),")]
354/// Transform::from_xyz(-10.0, -3.0, 0.0),
355/// ));
356///
357/// // Spawn a thin, long object rotating at a high speed.
358/// // The first ball should hit it, but the second one does not consider
359/// // rotational motion, and most likely passes through.
360/// commands.spawn((
361/// RigidBody::Dynamic,
362/// LockedAxes::TRANSLATION_LOCKED,
363#[cfg_attr(feature = "2d", doc = " AngularVelocity(100.0),")]
364#[cfg_attr(feature = "3d", doc = " AngularVelocity(Vec3::Z * 100.0),")]
365#[cfg_attr(feature = "2d", doc = " Collider::rectangle(0.2, 10.0),")]
366#[cfg_attr(feature = "3d", doc = " Collider::cuboid(0.2, 10.0, 10.0),")]
367/// ));
368///
369/// // Spawn another thin, long object, this time not rotating.
370/// // The second ball should now hit this.
371/// commands.spawn((
372/// RigidBody::Static,
373#[cfg_attr(feature = "2d", doc = " Collider::rectangle(0.2, 10.0),")]
374#[cfg_attr(feature = "3d", doc = " Collider::cuboid(0.2, 10.0, 10.0),")]
375/// Transform::from_xyz(15.0, 0.0, 0.0),
376/// ));
377/// }
378/// ```
379#[derive(Component, Clone, Copy, Debug, PartialEq, Reflect)]
380#[reflect(Component)]
381pub struct SweptCcd {
382 /// The type of sweep used for swept CCD.
383 ///
384 /// If two entities with different sweep modes collide, [`SweepMode::NonLinear`]
385 /// is preferred.
386 ///
387 /// The default is [`SweepMode::NonLinear`], which considers both translational
388 /// and rotational motion.
389 pub mode: SweepMode,
390 /// If `true`, swept CCD is performed against dynamic rigid bodies.
391 /// Otherwise, it is only performed against static geometry and kinematic bodies.
392 ///
393 /// The default is `true`.
394 pub include_dynamic: bool,
395 /// Determines how fast two bodies must be moving relative to each other
396 /// for swept CCD to be activated for them.
397 ///
398 /// If the linear velocity is below this threshold, CCD is skipped,
399 /// unless the angular velocity exceeds the `angular_threshold`.
400 ///
401 /// The default is `0.0`, meaning that CCD is performed regardless of the relative velocity.
402 pub linear_threshold: Scalar,
403 /// Determines how fast two bodies must be rotating relative to each other
404 /// for swept CCD to be activated for them.
405 ///
406 /// If the angular velocity is below this threshold, CCD is skipped,
407 /// unless the linear velocity exceeds the `linear_threshold`.
408 ///
409 /// The default is `0.0`, meaning that CCD is performed regardless of the relative velocity.
410 pub angular_threshold: Scalar,
411}
412
413impl Default for SweptCcd {
414 fn default() -> Self {
415 Self::NON_LINEAR
416 }
417}
418
419impl SweptCcd {
420 /// Continuous Collision Detection with [`SweepMode::Linear`].
421 ///
422 /// This only takes into account translational motion, and can lead to tunneling
423 /// against thin, fast-spinning objects.
424 pub const LINEAR: Self = Self::new_with_mode(SweepMode::Linear);
425
426 /// Continuous Collision Detection with [`SweepMode::NonLinear`].
427 ///
428 /// This takes into account both translational and rotational motion.
429 pub const NON_LINEAR: Self = Self::new_with_mode(SweepMode::NonLinear);
430
431 /// Creates a new [`SweptCcd`] configuration with the given [`SweepMode`].
432 #[inline]
433 pub const fn new_with_mode(mode: SweepMode) -> Self {
434 Self {
435 mode,
436 include_dynamic: true,
437 linear_threshold: 0.0,
438 angular_threshold: 0.0,
439 }
440 }
441
442 /// Sets the linear and angular velocity thresholds in `self`,
443 /// determining how fast two bodies must be moving relative to each other
444 /// for swept CCD to be activated for them.
445 ///
446 /// CCD will be active if either of the two thresholds is exceeded.
447 #[inline]
448 pub const fn with_velocity_threshold(mut self, linear: Scalar, angular: Scalar) -> Self {
449 self.linear_threshold = linear;
450 self.angular_threshold = angular;
451 self
452 }
453
454 /// Sets whether swept CCD is performed against dynamic rigid bodies.
455 /// If `false`, it is only performed against static geometry and kinematic bodies.
456 #[inline]
457 pub const fn include_dynamic(mut self, should_include: bool) -> Self {
458 self.include_dynamic = should_include;
459 self
460 }
461}
462
463/// The algorithm used for [Swept Continuous Collision Detection](self#swept-ccd).
464///
465/// If two entities with different sweep modes collide, [`SweepMode::NonLinear`]
466/// is preferred.
467///
468/// The default is [`SweepMode::NonLinear`], which considers both translational
469/// and rotational motion.
470#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Reflect)]
471pub enum SweepMode {
472 /// [Swept CCD](self#swept-ccd) is performed using linear time-of-impact queries
473 /// from the previous positions of [`SweptCcd`] bodies to their current positions,
474 /// stopping the bodies at the first time of impact.
475 ///
476 /// This mode only considers translational motion, and can lead to tunneling
477 /// against thin, fast-spinning objects. For the more expensive version
478 /// that also considers rotational motion, consider using [`SweepMode::NonLinear`].
479 Linear,
480
481 /// [Swept CCD](self#swept-ccd) is performed using non-linear time-of-impact queries
482 /// from the previous positions of [`SweptCcd`] bodies to their current positions,
483 /// stopping the bodies at the first time of impact.
484 ///
485 /// This mode considers both translational and rotational motion.
486 /// For the cheaper version that only considers translational motion,
487 /// consider using [`SweepMode::Linear`].
488 #[default]
489 NonLinear,
490}
491
492#[cfg(any(feature = "parry-f32", feature = "parry-f64"))]
493#[derive(QueryData)]
494#[query_data(mutable)]
495struct SweptCcdBodyQuery {
496 entity: Entity,
497 rb: &'static RigidBody,
498 pos: &'static Position,
499 translation: Option<&'static mut AccumulatedTranslation>,
500 rot: &'static mut Rotation,
501 prev_rot: Option<&'static mut PreviousRotation>,
502 lin_vel: Option<&'static LinearVelocity>,
503 ang_vel: Option<&'static AngularVelocity>,
504 ccd: Option<&'static SweptCcd>,
505 collider: &'static Collider,
506 com: &'static ComputedCenterOfMass,
507}
508
509/// Performs [sweep-based mContinuous Collision Detection](self#swept-ccd)
510/// by performing time-of-impact queries from the previous positions of [`SweptCcd`] bodies
511/// to their current positions, stopping the bodies at the first time of impact.
512///
513/// This approach can lead to "time loss" or "time stealing", because the bodies
514/// are essentially moved back in time, making them appear to momentarily move slower.
515/// Secondary contacts are also not accounted for.
516#[allow(clippy::useless_conversion)]
517#[cfg(any(feature = "parry-f32", feature = "parry-f64"))]
518fn solve_swept_ccd(
519 ccd_query: Query<Entity, With<SweptCcd>>,
520 bodies: Query<SweptCcdBodyQuery>,
521 colliders: Query<(&Collider, &ColliderOf)>,
522 time: Res<Time>,
523 contact_graph: Res<ContactGraph>,
524 narrow_phase_config: Res<NarrowPhaseConfig>,
525 mut diagnostics: ResMut<SolverDiagnostics>,
526) {
527 let start = crate::utils::Instant::now();
528
529 let delta_secs = time.delta_seconds_adjusted();
530
531 // TODO: Parallelize.
532 for entity in &ccd_query {
533 // Get the CCD body.
534 let Ok(SweptCcdBodyQueryItem {
535 pos: pos1,
536 translation: Some(mut translation1),
537 rot: mut rot1,
538 prev_rot: Some(prev_rot),
539 lin_vel: Some(lin_vel1),
540 ang_vel: Some(ang_vel1),
541 ccd: Some(ccd1),
542 collider: collider1,
543 com: com1,
544 ..
545 }) = (
546 // Safety: `get_unchecked` is only unsafe if there are multiple mutable references
547 // to the same component, and this is ensured not to happen when iterating
548 // over the AABB intersections below.
549 unsafe { bodies.get_unchecked(entity) }
550 )
551 else {
552 continue;
553 };
554
555 // The smallest time of impact found. Starts at the largest value,
556 // how long a body moves during a single frame due to position integration.
557 let (mut min_toi, mut min_toi_entity) = (delta_secs, None);
558
559 // Iterate through colliders intersecting the AABB of the CCD body.
560 let intersecting_entities = contact_graph.entities_colliding_with(entity);
561 for (collider2, &ColliderOf { body: entity2 }) in colliders.iter_many(intersecting_entities)
562 {
563 debug_assert_ne!(entity, entity2, "collider AABB cannot intersect itself");
564
565 // Get the body associated with the collider.
566 // Safety: `AabbIntersections` should never contain the entity of a collider
567 // attached to the first body, and the entities are also ensured to be different above.
568 if let Ok(body2) = unsafe { bodies.get_unchecked(entity2) } {
569 if !ccd1.include_dynamic && body2.rb.is_dynamic() {
570 continue;
571 }
572
573 let lin_vel2 = body2.lin_vel.copied().unwrap_or_default().0;
574 let ang_vel2 = body2.ang_vel.copied().unwrap_or_default().0;
575
576 #[cfg(feature = "2d")]
577 let ang_vel_below_threshold =
578 (ang_vel1.0 - ang_vel2).abs() < ccd1.angular_threshold;
579 #[cfg(feature = "3d")]
580 let ang_vel_below_threshold =
581 (ang_vel1.0 - ang_vel2).length_squared() < ccd1.angular_threshold.powi(2);
582
583 // If both the relative linear and relative angular velocity
584 // are below the defined thresholds, skip this body.
585 if ang_vel_below_threshold
586 && (lin_vel1.0 - lin_vel2).length_squared() < ccd1.linear_threshold.powi(2)
587 {
588 continue;
589 }
590
591 let iso1 = make_isometry(pos1.0, prev_rot.0);
592 let iso2 = make_isometry(
593 body2.pos.0,
594 body2.prev_rot.as_ref().map_or(*body2.rot, |rot| rot.0),
595 );
596
597 // TODO: Support child colliders
598 let motion1 = NonlinearRigidMotion::new(
599 iso1,
600 com1.0.into(),
601 lin_vel1.0.into(),
602 ang_vel1.0.into(),
603 );
604 let motion2 = NonlinearRigidMotion::new(
605 iso2,
606 body2.com.0.into(),
607 lin_vel2.into(),
608 ang_vel2.into(),
609 );
610
611 let sweep_mode = if ccd1.mode == SweepMode::Linear
612 && body2.ccd.is_none_or(|ccd| ccd.mode == SweepMode::Linear)
613 {
614 SweepMode::Linear
615 } else {
616 SweepMode::NonLinear
617 };
618
619 if let Some(toi) = compute_ccd_toi(
620 sweep_mode,
621 &motion1,
622 collider1,
623 &motion2,
624 collider2,
625 min_toi,
626 narrow_phase_config.default_speculative_margin,
627 ) {
628 min_toi = toi;
629 min_toi_entity = Some(entity2);
630 }
631 }
632 }
633
634 // Advance the bodies from the previous poses to the first time of impact.
635 if let Some(Ok(mut body2)) =
636 min_toi_entity.map(|entity| unsafe { bodies.get_unchecked(entity) })
637 {
638 let collider_lin_vel = body2.lin_vel.copied().unwrap_or_default().0;
639 let collider_ang_vel = body2.ang_vel.copied().unwrap_or_default().0;
640
641 // Overshoot slightly to make sure the bodies advance and don't get stuck.
642 let min_toi = min_toi * 1.0001;
643
644 translation1.0 = min_toi * lin_vel1.0;
645
646 // TODO: Abstract the integration logic to reuse it here
647 #[cfg(feature = "2d")]
648 {
649 *rot1 = prev_rot.0 * Rotation::radians(ang_vel1.0 * min_toi);
650 }
651 #[cfg(feature = "3d")]
652 {
653 let delta_rot = Quaternion::from_scaled_axis(ang_vel1.0 * min_toi);
654 rot1.0 = delta_rot * prev_rot.0 .0;
655 *rot1 = rot1.fast_renormalize();
656 }
657
658 if let Some(mut collider_translation) = body2.translation {
659 collider_translation.0 = min_toi * collider_lin_vel;
660 }
661 if let Some(ref collider_prev_rot) = body2.prev_rot {
662 #[cfg(feature = "2d")]
663 {
664 *body2.rot =
665 collider_prev_rot.0 * Rotation::radians(collider_ang_vel * min_toi);
666 }
667 #[cfg(feature = "3d")]
668 {
669 let delta_rot = Quaternion::from_scaled_axis(collider_ang_vel * min_toi);
670
671 body2.rot.0 = delta_rot * collider_prev_rot.0 .0;
672 *body2.rot = body2.rot.fast_renormalize();
673 }
674 }
675 }
676 }
677
678 diagnostics.swept_ccd += start.elapsed();
679}
680
681/// Computes the time of impact for the motion of two objects for Continuous Collision Detection.
682/// If the TOI is larger than `min_toi` or the shapes never touch, `None` is returned.
683#[cfg(any(feature = "parry-f32", feature = "parry-f64"))]
684fn compute_ccd_toi(
685 mode: SweepMode,
686 motion1: &NonlinearRigidMotion,
687 collider1: &Collider,
688 motion2: &NonlinearRigidMotion,
689 collider2: &Collider,
690 min_toi: Scalar,
691 prediction_distance: Scalar,
692) -> Option<Scalar> {
693 if mode == SweepMode::Linear {
694 if let Ok(Some(ShapeCastHit {
695 time_of_impact: toi,
696 ..
697 })) = cast_shapes(
698 &motion1.start,
699 &motion1.linvel,
700 collider1.shape_scaled().as_ref(),
701 &motion2.start,
702 &motion2.linvel,
703 collider2.shape_scaled().as_ref(),
704 ShapeCastOptions {
705 max_time_of_impact: min_toi,
706 stop_at_penetration: false,
707 ..default()
708 },
709 ) {
710 if toi > 0.0 && toi < min_toi {
711 // New smaller time of impact found
712 return Some(toi);
713 } else if toi == 0.0 {
714 // If the time of impact is zero, fall back to computing the TOI of a small circle
715 // around the centroid of the first body.
716 if let Ok(Some(ShapeCastHit {
717 time_of_impact: toi,
718 ..
719 })) = cast_shapes(
720 &motion1.start,
721 &motion1.linvel,
722 collider1.shape_scaled().as_ref(),
723 &motion2.start,
724 &motion2.linvel,
725 &parry::shape::Ball::new(prediction_distance),
726 ShapeCastOptions {
727 max_time_of_impact: min_toi,
728 stop_at_penetration: false,
729 ..default()
730 },
731 ) {
732 if toi > 0.0 && toi < min_toi {
733 // New smaller time of impact found
734 return Some(toi);
735 }
736 }
737 }
738 }
739 } else if let Ok(Some(ShapeCastHit {
740 time_of_impact: toi,
741 ..
742 })) = cast_shapes_nonlinear(
743 motion1,
744 collider1.shape_scaled().as_ref(),
745 motion2,
746 collider2.shape_scaled().as_ref(),
747 0.0,
748 min_toi,
749 false,
750 ) {
751 if toi > 0.0 && toi < min_toi {
752 // New smaller time of impact found
753 return Some(toi);
754 } else if toi == 0.0 {
755 // If the time of impact is zero, fall back to computing the TOI of a small circle
756 // around the centroid of the first body.
757 if let Ok(Some(ShapeCastHit {
758 time_of_impact: toi,
759 ..
760 })) = cast_shapes_nonlinear(
761 motion1,
762 collider1.shape_scaled().as_ref(),
763 motion2,
764 &parry::shape::Ball::new(prediction_distance),
765 0.0,
766 min_toi,
767 false,
768 ) {
769 if toi > 0.0 && toi < min_toi {
770 // New smaller time of impact found
771 return Some(toi);
772 }
773 }
774 }
775 }
776
777 None
778}