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author | eug-vs <eugene@eug-vs.xyz> | 2024-12-15 13:17:43 +0100 |
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committer | eug-vs <eugene@eug-vs.xyz> | 2024-12-15 13:17:43 +0100 |
commit | 70afc5a7d871919776a64782e8b93404e6b0defd (patch) | |
tree | c3d8a273bddf4cbc3c55d06c751766b93b961a1f /src/constraint/mod.rs | |
parent | 297efa5127e83bea57132c503680dd348a725db5 (diff) | |
download | particle-physics-70afc5a7d871919776a64782e8b93404e6b0defd.tar.gz |
feat!: add raylib rendering
Diffstat (limited to 'src/constraint/mod.rs')
-rw-r--r-- | src/constraint/mod.rs | 139 |
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"), - } - } -} |