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use crate::prelude::*;
use bevy::{
ecs::system::{
SystemParam,
lifetimeless::{Read, Write},
},
prelude::*,
};
/// A [`SystemParam`] that provides helper methods for computing and updating [mass properties].
///
/// [mass properties]: crate::dynamics::rigid_body::mass_properties
#[derive(SystemParam)]
pub struct MassPropertyHelper<'w, 's> {
query: Query<
'w,
's,
(
Option<Read<Mass>>,
Option<Read<AngularInertia>>,
Option<Read<CenterOfMass>>,
Option<Read<ColliderMassProperties>>,
Option<Read<ColliderTransform>>,
Has<Sensor>,
),
Or<(
With<Mass>,
With<AngularInertia>,
With<CenterOfMass>,
(
With<ColliderMassProperties>,
With<ColliderTransform>,
Without<Sensor>,
),
)>,
>,
computed_mass_properties_query: Query<
'w,
's,
(
Write<ComputedMass>,
Write<ComputedAngularInertia>,
Write<ComputedCenterOfMass>,
Option<Read<Mass>>,
Option<Read<AngularInertia>>,
Option<Read<CenterOfMass>>,
Has<NoAutoMass>,
Has<NoAutoAngularInertia>,
Has<NoAutoCenterOfMass>,
),
>,
children: Query<'w, 's, Read<Children>>,
}
impl MassPropertyHelper<'_, '_> {
/// Updates the [`ComputedMass`], [`ComputedAngularInertia`], and [`ComputedCenterOfMass`] of the given entity.
///
/// This takes into account the mass properties of descendants, unless the given entity has the [`NoAutoMass`],
/// [`NoAutoAngularInertia`], or [`NoAutoCenterOfMass`] marker components.
pub fn update_mass_properties(&mut self, entity: Entity) {
// Compute the total mass properties of the entity and its descendants.
let mut mass_props = self.total_mass_properties(entity);
let Ok((
mut computed_mass,
mut computed_inertia,
mut computed_com,
mass,
angular_inertia,
center_of_mass,
no_auto_mass,
no_auto_inertia,
no_auto_com,
)) = self.computed_mass_properties_query.get_mut(entity)
else {
return;
};
// If automatic computation of mass properties is disabled, set them to the local `Mass`, `AngularInertia`, and `CenterOfMass`.
// Otherwise, use the computed total mass properties.
if no_auto_mass {
if let Some(mass) = mass {
mass_props.set_mass(mass.0, !no_auto_inertia);
computed_mass.set(mass_props.mass as Scalar);
} else if !no_auto_inertia {
// Make sure the angular inertia is scaled to match the existing computed mass.
#[allow(clippy::unnecessary_cast)]
mass_props.set_mass(computed_mass.value() as f32, true);
}
} else {
computed_mass.set(mass_props.mass as Scalar);
}
if no_auto_inertia {
if let Some(angular_inertia) = angular_inertia {
#[cfg(feature = "2d")]
{
mass_props.angular_inertia = angular_inertia.0;
computed_inertia.set(mass_props.angular_inertia as Scalar);
}
#[cfg(feature = "3d")]
{
mass_props.principal_angular_inertia = angular_inertia.principal;
mass_props.local_inertial_frame = angular_inertia.local_frame;
*computed_inertia = ComputedAngularInertia::new_with_local_frame(
mass_props.principal_angular_inertia.adjust_precision(),
mass_props.local_inertial_frame.adjust_precision(),
);
}
}
} else {
#[cfg(feature = "2d")]
{
computed_inertia.set(mass_props.angular_inertia as Scalar);
}
#[cfg(feature = "3d")]
{
*computed_inertia = ComputedAngularInertia::new_with_local_frame(
mass_props.principal_angular_inertia.adjust_precision(),
mass_props.local_inertial_frame.adjust_precision(),
);
}
}
if no_auto_com {
if let Some(center_of_mass) = center_of_mass {
mass_props.center_of_mass = center_of_mass.0;
computed_com.0 = mass_props.center_of_mass.adjust_precision();
}
} else {
computed_com.0 = mass_props.center_of_mass.adjust_precision();
}
}
/// Computes the total mass properties of the given entity,
/// taking into account the mass properties of descendants.
///
/// This ignores the [`NoAutoMass`], [`NoAutoAngularInertia`], and [`NoAutoCenterOfMass`] marker components.
pub fn total_mass_properties(&self, entity: Entity) -> MassProperties {
core::iter::once(self.local_mass_properties(entity))
.chain(
self.children
.iter_descendants(entity)
.map(|child| self.local_mass_properties(child)),
)
.flatten()
.sum()
}
/// Computes the total mass properties of the descendants of the given entity.
///
/// This ignores the [`NoAutoMass`], [`NoAutoAngularInertia`], and [`NoAutoCenterOfMass`] marker components.
pub fn descendants_mass_properties(&self, entity: Entity) -> MassProperties {
self.children
.iter_descendants(entity)
.filter_map(|child| self.local_mass_properties(child))
.sum()
}
/// Computes the local mass properties of the given entity.
///
/// This only considers the entity's own [`Mass`], [`AngularInertia`], [`CenterOfMass`],
/// and/or [`ColliderMassProperties`] if present, not those of its children.
///
/// If the entity has no mass properties or the entity does not exist, `None` is returned.
pub fn local_mass_properties(&self, entity: Entity) -> Option<MassProperties> {
let (mass, angular_inertia, center_of_mass, collider_mass, collider_transform, is_sensor) =
self.query.get(entity).ok()?;
// Initialize the mass properties with the collider's mass properties or zero.
let mut mass_props = collider_mass
.filter(|_| !is_sensor)
.map_or(MassProperties::ZERO, |m| **m);
// Set the mass if the `Mass` component is present.
if let Some(mass) = mass {
// TODO: This needs to consider `NoAutoMass`.
// Only adjust the angular inertia if it is not exlicitly set with `AngularInertia`.
let update_angular_inertia = angular_inertia.is_none();
mass_props.set_mass(mass.0, update_angular_inertia);
}
// Set the angular inertia if the `AngularInertia` component is present.
if let Some(angular_inertia) = angular_inertia {
#[cfg(feature = "2d")]
{
mass_props.angular_inertia = angular_inertia.0;
}
#[cfg(feature = "3d")]
{
mass_props.principal_angular_inertia = angular_inertia.principal;
mass_props.local_inertial_frame = angular_inertia.local_frame;
}
}
// Set the center of mass if the `CenterOfMass` component is present.
if let Some(center_of_mass) = center_of_mass {
mass_props.center_of_mass = center_of_mass.0;
}
if let Some(collider_transform) = collider_mass.and(collider_transform) {
#[cfg(feature = "2d")]
{
mass_props.transform_by(Isometry2d::new(
collider_transform.translation.f32(),
Rot2::from(collider_transform.rotation),
));
}
#[cfg(feature = "3d")]
{
mass_props.transform_by(Isometry3d::new(
collider_transform.translation.f32(),
collider_transform.rotation.f32(),
));
}
}
Some(mass_props)
}
}