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use crate::dynamics::{FixedJoint, IntegrationParameters, RigidBody};
use crate::math::{AngularInertia, Isometry, Point, Real, Rotation};
use crate::utils::WAngularInertia;
#[derive(Debug)]
pub(crate) struct FixedPositionConstraint {
position1: usize,
position2: usize,
local_anchor1: Isometry<Real>,
local_anchor2: Isometry<Real>,
local_com1: Point<Real>,
local_com2: Point<Real>,
im1: Real,
im2: Real,
ii1: AngularInertia<Real>,
ii2: AngularInertia<Real>,
lin_inv_lhs: Real,
ang_inv_lhs: AngularInertia<Real>,
}
impl FixedPositionConstraint {
pub fn from_params(rb1: &RigidBody, rb2: &RigidBody, cparams: &FixedJoint) -> Self {
let ii1 = rb1.effective_world_inv_inertia_sqrt.squared();
let ii2 = rb2.effective_world_inv_inertia_sqrt.squared();
let im1 = rb1.effective_inv_mass;
let im2 = rb2.effective_inv_mass;
let lin_inv_lhs = 1.0 / (im1 + im2);
let ang_inv_lhs = (ii1 + ii2).inverse();
Self {
local_anchor1: cparams.local_anchor1,
local_anchor2: cparams.local_anchor2,
position1: rb1.active_set_offset,
position2: rb2.active_set_offset,
im1,
im2,
ii1,
ii2,
local_com1: rb1.mass_properties.local_com,
local_com2: rb2.mass_properties.local_com,
lin_inv_lhs,
ang_inv_lhs,
}
}
pub fn solve(&self, params: &IntegrationParameters, positions: &mut [Isometry<Real>]) {
let mut position1 = positions[self.position1 as usize];
let mut position2 = positions[self.position2 as usize];
// Angular correction.
let anchor1 = position1 * self.local_anchor1;
let anchor2 = position2 * self.local_anchor2;
let ang_err = anchor2.rotation * anchor1.rotation.inverse();
#[cfg(feature = "dim3")]
let ang_impulse = self
.ang_inv_lhs
.transform_vector(ang_err.scaled_axis() * params.joint_erp);
#[cfg(feature = "dim2")]
let ang_impulse = self
.ang_inv_lhs
.transform_vector(ang_err.angle() * params.joint_erp);
position1.rotation =
Rotation::new(self.ii1.transform_vector(ang_impulse)) * position1.rotation;
position2.rotation =
Rotation::new(self.ii2.transform_vector(-ang_impulse)) * position2.rotation;
// Linear correction.
let anchor1 = position1 * Point::from(self.local_anchor1.translation.vector);
let anchor2 = position2 * Point::from(self.local_anchor2.translation.vector);
let err = anchor2 - anchor1;
let impulse = err * (self.lin_inv_lhs * params.joint_erp);
position1.translation.vector += self.im1 * impulse;
position2.translation.vector -= self.im2 * impulse;
positions[self.position1 as usize] = position1;
positions[self.position2 as usize] = position2;
}
}
#[derive(Debug)]
pub(crate) struct FixedPositionGroundConstraint {
position2: usize,
anchor1: Isometry<Real>,
local_anchor2: Isometry<Real>,
local_com2: Point<Real>,
im2: Real,
ii2: AngularInertia<Real>,
impulse: Real,
}
impl FixedPositionGroundConstraint {
pub fn from_params(
rb1: &RigidBody,
rb2: &RigidBody,
cparams: &FixedJoint,
flipped: bool,
) -> Self {
let anchor1;
let local_anchor2;
if flipped {
anchor1 = rb1.predicted_position * cparams.local_anchor2;
local_anchor2 = cparams.local_anchor1;
} else {
anchor1 = rb1.predicted_position * cparams.local_anchor1;
local_anchor2 = cparams.local_anchor2;
};
Self {
anchor1,
local_anchor2,
position2: rb2.active_set_offset,
im2: rb2.effective_inv_mass,
ii2: rb2.effective_world_inv_inertia_sqrt.squared(),
local_com2: rb2.mass_properties.local_com,
impulse: 0.0,
}
}
pub fn solve(&self, params: &IntegrationParameters, positions: &mut [Isometry<Real>]) {
let mut position2 = positions[self.position2 as usize];
// Angular correction.
let anchor2 = position2 * self.local_anchor2;
let ang_err = anchor2.rotation * self.anchor1.rotation.inverse();
position2.rotation = ang_err.powf(-params.joint_erp) * position2.rotation;
// Linear correction.
let anchor1 = Point::from(self.anchor1.translation.vector);
let anchor2 = position2 * Point::from(self.local_anchor2.translation.vector);
let err = anchor2 - anchor1;
// NOTE: no need to divide by im2 just to multiply right after.
let impulse = err * params.joint_erp;
position2.translation.vector -= impulse;
positions[self.position2 as usize] = position2;
}
}
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