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use nalgebra::{DVector, RowDVector};
use crate::algebra::distance_field::DistanceField;
use crate::algebra::subspace::{Line, Subspace};
use crate::algebra::{Point, Scalar, N};
use crate::particle_system::ParticleSystem;
use super::Constraint;
/// Keep a particle at certain distance within distance field
pub struct DistanceConstraint<D: DistanceField> {
particle_id: usize,
distance_field: D,
distance: Scalar,
}
impl ParticleSystem {
pub fn add_distance_constraint<const DIM: usize>(&mut self, particle_id: usize, subspace: Subspace<DIM>, distance: Scalar) {
let particle = &self.particles[particle_id];
self.constraints.push(Box::new(DistanceConstraint {
particle_id,
distance,
distance_field: subspace,
}));
}
}
impl<D: DistanceField> Constraint for DistanceConstraint<D> {
fn get_particles(&self) -> Vec<usize> {
vec![self.particle_id]
}
fn c(&self, q: &DVector<Scalar>) -> Scalar {
let position = q.fixed_rows::<N>(self.particle_id * N);
self.distance_field.distance(Point::from_coordinates(position.into())) - self.distance
}
fn jacobian(&self, q: &DVector<Scalar>) -> RowDVector<Scalar> {
let point = Point::from_coordinates(q.fixed_rows::<N>(self.particle_id * N).into());
let normal = self.distance_field.project_point(point) - point;
let mut result = RowDVector::zeros(q.len());
for i in 0..N {
result[self.particle_id * N + i] = normal[i];
}
result
}
}
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