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authoreug-vs <eugene@eug-vs.xyz>2024-12-15 13:17:43 +0100
committereug-vs <eugene@eug-vs.xyz>2024-12-15 13:17:43 +0100
commit70afc5a7d871919776a64782e8b93404e6b0defd (patch)
treec3d8a273bddf4cbc3c55d06c751766b93b961a1f /src/constraint/mod.rs
parent297efa5127e83bea57132c503680dd348a725db5 (diff)
downloadparticle-physics-70afc5a7d871919776a64782e8b93404e6b0defd.tar.gz
feat!: add raylib rendering
Diffstat (limited to 'src/constraint/mod.rs')
-rw-r--r--src/constraint/mod.rs139
1 files changed, 0 insertions, 139 deletions
diff --git a/src/constraint/mod.rs b/src/constraint/mod.rs
deleted file mode 100644
index 6028b42..0000000
--- a/src/constraint/mod.rs
+++ /dev/null
@@ -1,139 +0,0 @@
-use nalgebra::{DMatrix, DVector, RowDVector};
-
-use crate::particle_system::{ParticleSystem, Scalar, Vector, N};
-pub mod anchor;
-pub mod slider;
-pub mod beam;
-
-const SPRING_CONSTANT: Scalar = 0.75;
-const DAMPING_CONSTANT: Scalar = 0.45;
-
-/// SIZE is always 3xN, but this operation can't be done at compile time yet:
-/// "generic parameters may not be used in const operations"
-pub trait Constraint {
- fn get_particles(&self) -> Vec<usize>;
-
- fn c(&self, q: &DVector<Scalar>) -> Scalar;
-
- fn jacobian_prev(&self) -> RowDVector<Scalar>;
- fn set_jacobian(&mut self, jacobian: RowDVector<Scalar>);
-
- fn partial_derivative(&self, q: &DVector<Scalar>) -> RowDVector<Scalar> {
- let dq = 0.001;
- let c_original = self.c(&q);
- let mut result = RowDVector::zeros(q.len());
- // The only non-zero components of derivative vector are
- // the particles that this constraint affects
- for particle_id in self.get_particles() {
- for i in 0..N {
- let index = particle_id * N + i;
- let mut q_partial = q.clone();
- q_partial[index] += dq;
-
- let c = self.c(&q_partial);
-
- result[index] = (c - c_original) / dq
- }
- }
-
- result
- }
-
- fn compute(
- &mut self,
- q: &DVector<Scalar>,
- q_prev: &DVector<Scalar>,
- dt: Scalar,
- ) -> (Scalar, Scalar, RowDVector<Scalar>, RowDVector<Scalar>) {
- let c = self.c(q);
- let c_prev = self.c(q_prev);
-
- let c_dot = (c - c_prev) / dt;
-
- let jacobian = self.partial_derivative(&q);
-
- let jacobian_dot = (jacobian.clone() - self.jacobian_prev()) / dt;
- self.set_jacobian(jacobian.clone());
-
- (c, c_dot, jacobian, jacobian_dot)
- }
-}
-
-impl ParticleSystem {
- pub fn enforce_constraints(&mut self, dt: Scalar) {
- if self.constraints.len() == 0 {
- return
- }
-
- let size = self.particles.len() * N;
- let mut q = DVector::zeros(size);
- let mut q_prev = DVector::zeros(size);
-
- for (p, particle) in self.particles.iter().enumerate() {
- for i in 0..N {
- q[p * N + i] = particle.position[i];
- q_prev[p * N + i] = particle.position[i] - particle.velocity[i] * dt;
- }
- }
-
- let q_dot = (q.clone() - q_prev.clone()) / dt;
-
- let mut c = DVector::zeros(self.constraints.len());
- let mut c_dot = DVector::zeros(self.constraints.len());
- let mut jacobian = DMatrix::<Scalar>::zeros(self.constraints.len(), size);
- let mut jacobian_dot = DMatrix::<Scalar>::zeros(self.constraints.len(), size);
-
- for (constraint_id, constraint) in self.constraints.iter_mut().enumerate() {
- let (value, derivative, j, jdot) = constraint.compute(&q, &q_prev, dt);
- jacobian.set_row(constraint_id, &j);
- jacobian_dot.set_row(constraint_id, &jdot);
- c[constraint_id] = value;
- c_dot[constraint_id] = derivative;
- }
-
- // println!("C {}\nC' {}", c, c_dot);
- // println!("J = {}", jacobian.clone());
- // println!("J' = {}", jacobian_dot.clone());
-
- let mut w = DMatrix::zeros(size, size);
- for (i, particle) in self.particles.iter().enumerate() {
- for j in 0..N {
- *w.index_mut((i * N + j, i * N + j)) = 1.0 / particle.mass;
- }
- }
-
- let mut forces = DVector::zeros(size);
- for (p, particle) in self.particles.iter().enumerate() {
- for i in 0..N {
- forces[p * N + i] = particle.force[i];
- }
- }
-
- let lhs = jacobian.clone() * w.clone() * jacobian.transpose();
- // println!("LHS {}", lhs);
-
- let rhs = -(jacobian_dot * q_dot
- + jacobian.clone() * w * forces
- + SPRING_CONSTANT * c
- + DAMPING_CONSTANT * c_dot);
-
- // println!("RHS {}", rhs);
-
- match lhs.lu().solve(&rhs) {
- Some(lambda) => {
- // println!("Lambda = {}", lambda);
- let constraint_force = jacobian.transpose() * lambda;
-
- for i in 0..self.particles.len() {
- let mut force = Vector::zeros();
- for j in 0..N {
- force[j] = constraint_force[i * N + j];
- }
-
- self.particles[i].apply_force(force);
- }
- }
- None => println!("Lambda not found"),
- }
- }
-}