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use super::AnyPositionConstraint;
use crate::dynamics::{IntegrationParameters, RigidBodySet};
use crate::geometry::ContactManifold;
use crate::math::{
AngularInertia, Isometry, Point, Real, Rotation, Translation, Vector, MAX_MANIFOLD_POINTS,
};
use crate::utils::{WAngularInertia, WCross, WDot};
pub(crate) struct PositionGroundConstraint {
pub rb2: usize,
// NOTE: the points are relative to the center of masses.
pub p1: [Point<Real>; MAX_MANIFOLD_POINTS],
pub local_p2: [Point<Real>; MAX_MANIFOLD_POINTS],
pub dists: [Real; MAX_MANIFOLD_POINTS],
pub n1: Vector<Real>,
pub num_contacts: u8,
pub im2: Real,
pub ii2: AngularInertia<Real>,
pub erp: Real,
pub max_linear_correction: Real,
}
impl PositionGroundConstraint {
pub fn generate(
params: &IntegrationParameters,
manifold: &ContactManifold,
bodies: &RigidBodySet,
out_constraints: &mut Vec<AnyPositionConstraint>,
push: bool,
) {
let mut rb1 = &bodies[manifold.data.body_pair.body1];
let mut rb2 = &bodies[manifold.data.body_pair.body2];
let flip = manifold.data.relative_dominance < 0;
let n1 = if flip {
std::mem::swap(&mut rb1, &mut rb2);
-manifold.data.normal
} else {
manifold.data.normal
};
for (l, manifold_contacts) in manifold
.data
.solver_contacts
.chunks(MAX_MANIFOLD_POINTS)
.enumerate()
{
let mut p1 = [Point::origin(); MAX_MANIFOLD_POINTS];
let mut local_p2 = [Point::origin(); MAX_MANIFOLD_POINTS];
let mut dists = [0.0; MAX_MANIFOLD_POINTS];
for k in 0..manifold_contacts.len() {
p1[k] = manifold_contacts[k].point;
local_p2[k] = rb2
.position
.inverse_transform_point(&manifold_contacts[k].point);
dists[k] = manifold_contacts[k].dist;
}
let constraint = PositionGroundConstraint {
rb2: rb2.active_set_offset,
p1,
local_p2,
n1,
dists,
im2: rb2.effective_inv_mass,
ii2: rb2.effective_world_inv_inertia_sqrt.squared(),
num_contacts: manifold_contacts.len() as u8,
erp: params.erp,
max_linear_correction: params.max_linear_correction,
};
if push {
out_constraints.push(AnyPositionConstraint::NonGroupedGround(constraint));
} else {
out_constraints[manifold.data.constraint_index + l] =
AnyPositionConstraint::NonGroupedGround(constraint);
}
}
}
pub fn solve(&self, params: &IntegrationParameters, positions: &mut [Isometry<Real>]) {
// FIXME: can we avoid most of the multiplications by pos1/pos2?
// Compute jacobians.
let mut pos2 = positions[self.rb2];
let allowed_err = params.allowed_linear_error;
for k in 0..self.num_contacts as usize {
let target_dist = -self.dists[k] - allowed_err;
let n1 = self.n1;
let p1 = self.p1[k];
let p2 = pos2 * self.local_p2[k];
let dpos = p2 - p1;
let dist = dpos.dot(&n1);
if dist < target_dist {
let err = ((dist - target_dist) * self.erp).max(-self.max_linear_correction);
let dp2 = p2.coords - pos2.translation.vector;
let gcross2 = -dp2.gcross(n1);
let ii_gcross2 = self.ii2.transform_vector(gcross2);
// Compute impulse.
let inv_r = self.im2 + gcross2.gdot(ii_gcross2);
let impulse = err / inv_r;
// Apply impulse.
let tra2 = Translation::from(n1 * (-impulse * self.im2));
let rot2 = Rotation::new(ii_gcross2 * impulse);
pos2 = Isometry::from_parts(tra2 * pos2.translation, rot2 * pos2.rotation);
}
}
positions[self.rb2] = pos2;
}
}
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