Struct Restitution

pub struct Restitution {
    pub coefficient: Scalar,
    pub combine_rule: CoefficientCombine,
}

A component for restitution, controlling how bouncy a rigid body or collider is.

The coefficient should be between 0 and 1, where 0 corresponds to a perfectly inelastic collision with zero bounce, and 1 corresponds to a perfectly elastic collision that tries to preserve all kinetic energy. Values larger than 1 can result in unstable or explosive behavior.

If a collider does not have Restitution specified, the Restitution of its rigid body entity will be used instead. If that is not specified either, collisions use the DefaultRestitution resource. The default restitution is set to 0, meaning that objects are not bouncy by default.

Combine Rule

When two bodies collide, their coefficients are combined using the specified CoefficientCombine rule. In the case of clashing rules, the following priority order is used: Max > Multiply > Min > GeometricMean > Average.

By default, restitution uses CoefficientCombine::Average, computing the average (a + b) / 2.0.

Usage

Create a new Restitution component with a restitution coefficient of 0.4:

Restitution::new(0.4)

Configure how two restitution coefficients are combined with CoefficientCombine:

Restitution::new(0.4).with_combine_rule(CoefficientCombine::Max)

Combine the properties of two Restitution components:

let first = Restitution::new(0.8).with_combine_rule(CoefficientCombine::Average);
let second = Restitution::new(0.5).with_combine_rule(CoefficientCombine::Multiply);

// `CoefficientCombine::Multiply` has higher priority, so the coefficients are multiplied
assert_eq!(
    first.combine(second),
    Restitution::new(0.4).with_combine_rule(CoefficientCombine::Multiply)
);

Accuracy

Restitution is not guaranteed to be entirely accurate, especially for fast-moving bodies or when there are multiple contact points.

• Even with a coefficient of 1, some kinetic energy can be lost over long periods of time for bouncing objects. This can be caused by friction, damping, or simulation inaccuracies.

• Collisions can have more or less bounce than expected, especially when objects are moving very fast. This is largely due to the the sequential solver and speculative collision. For more accurate restitution, consider disabling speculative collision and using SweptCcd instead.

• An object falling flat on the ground with multiple contact points may tip over on one side or corner a bit. This is because contact points are solved sequentially, and the order of contact points affects the result. Configuring SolverConfig::restitution_iterations may help mitigate this.

• When collision velocity is small, collisions are treated as inelastic to prevent jitter. The velocity threshold can be configured using SolverConfig::restitution_threshold.

For game purposes however, restitution should still be reasonably accurate.

It is worth noting that in real life, restitution coefficients can vary greatly based on material combinations and numerous other factors, and they are not uniform across surfaces. For game purposes however, it is impractical to consider all of these factors, so instead, material interactions are controlled using simple CoefficientCombine rules.

Fields

coefficient: Scalar

The coefficient of restitution.

This should be between 0 and 1, where 0 corresponds to a perfectly inelastic collision with zero bounce, and 1 corresponds to a perfectly elastic collision that tries to preserve all kinetic energy. Values larger than 1 can result in unstable or explosive behavior.

Defaults to 0.0.

combine_rule: CoefficientCombine

The rule used for computing the combined coefficient of restitution when two bodies collide.

Defaults to CoefficientCombine::Average.

Implementations

impl Restitution

pub const ZERO: Self = _

A restitution coefficient of 0.0 and a combine rule of CoefficientCombine::Average.

This is equivalent to Restitution::PERFECTLY_INELASTIC.

pub const PERFECTLY_INELASTIC: Self = _

A restitution coefficient of 0.0, which corresponds to a perfectly inelastic collision.

Uses CoefficientCombine::Average.

pub const PERFECTLY_ELASTIC: Self = _

A restitution coefficient of 1.0, which corresponds to a perfectly elastic collision.

Uses CoefficientCombine::Average.

pub fn new(coefficient: Scalar) -> Self

Creates a new Restitution component with the given restitution coefficient.

pub fn with_combine_rule(&self, combine_rule: CoefficientCombine) -> Self

Sets the CoefficientCombine rule used.

pub fn combine(&self, other: Self) -> Self

Combines the properties of two Restitution components.

Trait Implementations

impl Clone for Restitution

fn clone(&self) -> Restitution

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Component for Restitution

where Self: Send + Sync + 'static,

const STORAGE_TYPE: StorageType = bevy::ecs::component::StorageType::Table

A constant indicating the storage type used for this component.

fn register_required_components( requiree: ComponentId, components: &mut Components, storages: &mut Storages, required_components: &mut RequiredComponents, inheritance_depth: u16, )

Registers required components.

fn register_component_hooks(hooks: &mut ComponentHooks)

Called when registering this component, allowing mutable access to its ComponentHooks.

impl Debug for Restitution

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Restitution

fn default() -> Self

The default Restitution with a coefficient of 0.0 and a combine rule of CoefficientCombine::Average.

impl From<f32> for Restitution

fn from(coefficient: Scalar) -> Self

Converts to this type from the input type.

impl FromReflect for Restitution

where Restitution: Any + Send + Sync, Scalar: FromReflect + TypePath + MaybeTyped + RegisterForReflection, CoefficientCombine: FromReflect + TypePath + MaybeTyped + RegisterForReflection,

fn from_reflect(reflect: &dyn PartialReflect) -> Option<Self>

Constructs a concrete instance of Self from a reflected value.

fn take_from_reflect( reflect: Box<dyn PartialReflect>, ) -> Result<Self, Box<dyn PartialReflect>>

Attempts to downcast the given value to Self using, constructing the value using from_reflect if that fails.

impl GetTypeRegistration for Restitution

where Restitution: Any + Send + Sync, Scalar: FromReflect + TypePath + MaybeTyped + RegisterForReflection, CoefficientCombine: FromReflect + TypePath + MaybeTyped + RegisterForReflection,

fn get_type_registration() -> TypeRegistration

Returns the default TypeRegistration for this type.

fn register_type_dependencies(registry: &mut TypeRegistry)

Registers other types needed by this type.

impl PartialEq for Restitution

fn eq(&self, other: &Restitution) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Restitution

fn partial_cmp(&self, other: &Restitution) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl PartialReflect for Restitution

where Restitution: Any + Send + Sync, Scalar: FromReflect + TypePath + MaybeTyped + RegisterForReflection, CoefficientCombine: FromReflect + TypePath + MaybeTyped + RegisterForReflection,

fn get_represented_type_info(&self) -> Option<&'static TypeInfo>

Returns the TypeInfo of the type represented by this value.

fn clone_value(&self) -> Box<dyn PartialReflect>

Clones the value as a Reflect trait object.

fn try_apply(&mut self, value: &dyn PartialReflect) -> Result<(), ApplyError>

Tries to apply a reflected value to this value.

fn reflect_kind(&self) -> ReflectKind

Returns a zero-sized enumeration of “kinds” of type.

fn reflect_ref(&self) -> ReflectRef<'_>

Returns an immutable enumeration of “kinds” of type.

fn reflect_mut(&mut self) -> ReflectMut<'_>

Returns a mutable enumeration of “kinds” of type.

fn reflect_owned(self: Box<Self>) -> ReflectOwned

Returns an owned enumeration of “kinds” of type.

fn try_into_reflect( self: Box<Self>, ) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>>

Attempts to cast this type to a boxed, fully-reflected value.

fn try_as_reflect(&self) -> Option<&dyn Reflect>

Attempts to cast this type to a fully-reflected value.

fn try_as_reflect_mut(&mut self) -> Option<&mut dyn Reflect>

Attempts to cast this type to a mutable, fully-reflected value.

fn into_partial_reflect(self: Box<Self>) -> Box<dyn PartialReflect>

Casts this type to a boxed, reflected value.

fn as_partial_reflect(&self) -> &dyn PartialReflect

Casts this type to a reflected value.

fn as_partial_reflect_mut(&mut self) -> &mut dyn PartialReflect

Casts this type to a mutable, reflected value.

fn reflect_partial_eq(&self, value: &dyn PartialReflect) -> Option<bool>

Returns a “partial equality” comparison result.

fn debug(&self, f: &mut Formatter<'_>) -> Result

Debug formatter for the value.

fn apply(&mut self, value: &(dyn PartialReflect + 'static))

Applies a reflected value to this value.

fn reflect_hash(&self) -> Option<u64>

Returns a hash of the value (which includes the type).

fn serializable(&self) -> Option<Serializable<'_>>

Returns a serializable version of the value.

fn is_dynamic(&self) -> bool

Indicates whether or not this type is a dynamic type.

impl Reflect for Restitution

where Restitution: Any + Send + Sync, Scalar: FromReflect + TypePath + MaybeTyped + RegisterForReflection, CoefficientCombine: FromReflect + TypePath + MaybeTyped + RegisterForReflection,

fn into_any(self: Box<Self>) -> Box<dyn Any>

Returns the value as a Box<dyn Any>.

fn as_any(&self) -> &dyn Any

Returns the value as a &dyn Any.

fn as_any_mut(&mut self) -> &mut dyn Any

Returns the value as a &mut dyn Any.

fn into_reflect(self: Box<Self>) -> Box<dyn Reflect>

Casts this type to a boxed, fully-reflected value.

fn as_reflect(&self) -> &dyn Reflect

Casts this type to a fully-reflected value.

fn as_reflect_mut(&mut self) -> &mut dyn Reflect

Casts this type to a mutable, fully-reflected value.

fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>>

Performs a type-checked assignment of a reflected value to this value.

impl Struct for Restitution

where Restitution: Any + Send + Sync, Scalar: FromReflect + TypePath + MaybeTyped + RegisterForReflection, CoefficientCombine: FromReflect + TypePath + MaybeTyped + RegisterForReflection,

fn field(&self, name: &str) -> Option<&dyn PartialReflect>

Returns a reference to the value of the field named name as a &dyn PartialReflect.

fn field_mut(&mut self, name: &str) -> Option<&mut dyn PartialReflect>

Returns a mutable reference to the value of the field named name as a &mut dyn PartialReflect.

fn field_at(&self, index: usize) -> Option<&dyn PartialReflect>

Returns a reference to the value of the field with index index as a &dyn PartialReflect.

fn field_at_mut(&mut self, index: usize) -> Option<&mut dyn PartialReflect>

Returns a mutable reference to the value of the field with index index as a &mut dyn PartialReflect.

fn name_at(&self, index: usize) -> Option<&str>

Returns the name of the field with index index.

fn field_len(&self) -> usize

Returns the number of fields in the struct.

fn iter_fields(&self) -> FieldIter<'_>

Returns an iterator over the values of the reflectable fields for this struct.

fn clone_dynamic(&self) -> DynamicStruct

Clones the struct into a DynamicStruct.

fn get_represented_struct_info(&self) -> Option<&'static StructInfo>

Will return None if TypeInfo is not available.

impl TypePath for Restitution

where Restitution: Any + Send + Sync,

fn type_path() -> &'static str

Returns the fully qualified path of the underlying type.

fn short_type_path() -> &'static str

Returns a short, pretty-print enabled path to the type.

fn type_ident() -> Option<&'static str>

Returns the name of the type, or None if it is anonymous.

fn crate_name() -> Option<&'static str>

Returns the name of the crate the type is in, or None if it is anonymous.

fn module_path() -> Option<&'static str>

Returns the path to the module the type is in, or None if it is anonymous.

impl Typed for Restitution

where Restitution: Any + Send + Sync, Scalar: FromReflect + TypePath + MaybeTyped + RegisterForReflection, CoefficientCombine: FromReflect + TypePath + MaybeTyped + RegisterForReflection,

fn type_info() -> &'static TypeInfo

Returns the compile-time info for the underlying type.

impl Copy for Restitution

impl StructuralPartialEq for Restitution