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use super::AnyPositionConstraint;
use crate::dynamics::{IntegrationParameters, RigidBodySet};
use crate::geometry::ContactManifold;
use crate::math::{
AngularInertia, Isometry, Point, Real, Rotation, SimdReal, Translation, Vector,
MAX_MANIFOLD_POINTS, SIMD_WIDTH,
};
use crate::utils::{WAngularInertia, WCross, WDot};
use num::Zero;
use simba::simd::{SimdBool as _, SimdPartialOrd, SimdValue};
pub(crate) struct WPositionGroundConstraint {
pub rb2: [usize; SIMD_WIDTH],
// NOTE: the points are relative to the center of masses.
pub p1: [Point<SimdReal>; MAX_MANIFOLD_POINTS],
pub local_p2: [Point<SimdReal>; MAX_MANIFOLD_POINTS],
pub dists: [SimdReal; MAX_MANIFOLD_POINTS],
pub n1: Vector<SimdReal>,
pub im2: SimdReal,
pub ii2: AngularInertia<SimdReal>,
pub erp: SimdReal,
pub max_linear_correction: SimdReal,
pub num_contacts: u8,
}
impl WPositionGroundConstraint {
pub fn generate(
params: &IntegrationParameters,
manifolds: [&ContactManifold; SIMD_WIDTH],
bodies: &RigidBodySet,
out_constraints: &mut Vec<AnyPositionConstraint>,
push: bool,
) {
let mut rbs1 =
array![|ii| bodies.get(manifolds[ii].data.body_pair.body1).unwrap(); SIMD_WIDTH];
let mut rbs2 =
array![|ii| bodies.get(manifolds[ii].data.body_pair.body2).unwrap(); SIMD_WIDTH];
let mut flipped = [false; SIMD_WIDTH];
for ii in 0..SIMD_WIDTH {
if !rbs2[ii].is_dynamic() {
flipped[ii] = true;
std::mem::swap(&mut rbs1[ii], &mut rbs2[ii]);
}
}
let im2 = SimdReal::from(array![|ii| rbs2[ii].effective_inv_mass; SIMD_WIDTH]);
let sqrt_ii2: AngularInertia<SimdReal> = AngularInertia::from(
array![|ii| rbs2[ii].effective_world_inv_inertia_sqrt; SIMD_WIDTH],
);
let n1 = Vector::from(
array![|ii| if flipped[ii] { -manifolds[ii].data.normal } else { manifolds[ii].data.normal }; SIMD_WIDTH],
);
let pos2 = Isometry::from(array![|ii| rbs2[ii].position; SIMD_WIDTH]);
let rb2 = array![|ii| rbs2[ii].island_offset; SIMD_WIDTH];
let num_active_contacts = manifolds[0].data.num_active_contacts();
for l in (0..num_active_contacts).step_by(MAX_MANIFOLD_POINTS) {
let manifold_points = array![|ii| &manifolds[ii].data.solver_contacts[l..]; SIMD_WIDTH];
let num_points = manifold_points[0].len().min(MAX_MANIFOLD_POINTS);
let mut constraint = WPositionGroundConstraint {
rb2,
p1: [Point::origin(); MAX_MANIFOLD_POINTS],
local_p2: [Point::origin(); MAX_MANIFOLD_POINTS],
n1,
dists: [SimdReal::zero(); MAX_MANIFOLD_POINTS],
im2,
ii2: sqrt_ii2.squared(),
erp: SimdReal::splat(params.position_erp),
max_linear_correction: SimdReal::splat(params.max_linear_correction),
num_contacts: num_points as u8,
};
for i in 0..num_points {
let point = Point::from(array![|ii| manifold_points[ii][i].point; SIMD_WIDTH]);
let dist = SimdReal::from(array![|ii| manifold_points[ii][i].dist; SIMD_WIDTH]);
constraint.p1[i] = point;
constraint.local_p2[i] = pos2.inverse_transform_point(&point);
constraint.dists[i] = dist;
}
if push {
out_constraints.push(AnyPositionConstraint::GroupedGround(constraint));
} else {
out_constraints[manifolds[0].data.constraint_index + l / MAX_MANIFOLD_POINTS] =
AnyPositionConstraint::GroupedGround(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 = Isometry::from(array![|ii| positions[self.rb2[ii]]; SIMD_WIDTH]);
let allowed_err = SimdReal::splat(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);
// NOTE: this condition does not seem to be useful perfomancewise?
if dist.simd_lt(target_dist).any() {
let err = ((dist - target_dist) * self.erp)
.simd_clamp(-self.max_linear_correction, SimdReal::zero());
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.
pos2.translation = Translation::from(n1 * (-impulse * self.im2)) * pos2.translation;
pos2.rotation = Rotation::new(ii_gcross2 * impulse) * pos2.rotation;
}
}
for ii in 0..SIMD_WIDTH {
positions[self.rb2[ii]] = pos2.extract(ii);
}
}
}
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