296 lines
12 KiB
Rust
296 lines
12 KiB
Rust
use super::{AnyVelocityConstraint, DeltaVel};
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use crate::math::{AngVector, Real, Vector, DIM, MAX_MANIFOLD_POINTS};
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use crate::utils::{WAngularInertia, WBasis, WCross, WDot};
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use crate::dynamics::{IntegrationParameters, RigidBodySet};
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use crate::geometry::{ContactManifold, ContactManifoldIndex};
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use simba::simd::SimdPartialOrd;
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#[derive(Copy, Clone, Debug)]
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pub(crate) struct VelocityGroundConstraintElementPart {
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pub gcross2: AngVector<Real>,
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pub rhs: Real,
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pub impulse: Real,
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pub r: Real,
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}
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#[cfg(not(target_arch = "wasm32"))]
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impl VelocityGroundConstraintElementPart {
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fn zero() -> Self {
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Self {
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gcross2: na::zero(),
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rhs: 0.0,
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impulse: 0.0,
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r: 0.0,
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}
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}
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}
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#[derive(Copy, Clone, Debug)]
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pub(crate) struct VelocityGroundConstraintElement {
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pub normal_part: VelocityGroundConstraintElementPart,
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pub tangent_part: [VelocityGroundConstraintElementPart; DIM - 1],
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}
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#[cfg(not(target_arch = "wasm32"))]
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impl VelocityGroundConstraintElement {
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pub fn zero() -> Self {
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Self {
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normal_part: VelocityGroundConstraintElementPart::zero(),
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tangent_part: [VelocityGroundConstraintElementPart::zero(); DIM - 1],
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}
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}
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}
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#[derive(Copy, Clone, Debug)]
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pub(crate) struct VelocityGroundConstraint {
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pub dir1: Vector<Real>, // Non-penetration force direction for the first body.
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pub im2: Real,
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pub limit: Real,
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pub mj_lambda2: usize,
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pub manifold_id: ContactManifoldIndex,
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pub manifold_contact_id: [u8; MAX_MANIFOLD_POINTS],
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pub num_contacts: u8,
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pub elements: [VelocityGroundConstraintElement; MAX_MANIFOLD_POINTS],
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}
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impl VelocityGroundConstraint {
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pub fn generate(
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params: &IntegrationParameters,
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manifold_id: ContactManifoldIndex,
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manifold: &ContactManifold,
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bodies: &RigidBodySet,
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out_constraints: &mut Vec<AnyVelocityConstraint>,
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push: bool,
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) {
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let inv_dt = params.inv_dt();
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let velocity_based_erp_inv_dt = params.velocity_based_erp_inv_dt();
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let mut rb1 = &bodies[manifold.data.body_pair.body1];
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let mut rb2 = &bodies[manifold.data.body_pair.body2];
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let flipped = manifold.data.relative_dominance < 0;
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let (force_dir1, flipped_multiplier) = if flipped {
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std::mem::swap(&mut rb1, &mut rb2);
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(manifold.data.normal, -1.0)
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} else {
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(-manifold.data.normal, 1.0)
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};
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let mj_lambda2 = rb2.active_set_offset;
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let warmstart_coeff = manifold.data.warmstart_multiplier * params.warmstart_coeff;
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for (_l, manifold_points) in manifold
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.data
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.solver_contacts
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.chunks(MAX_MANIFOLD_POINTS)
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.enumerate()
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{
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#[cfg(not(target_arch = "wasm32"))]
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let mut constraint = VelocityGroundConstraint {
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dir1: force_dir1,
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elements: [VelocityGroundConstraintElement::zero(); MAX_MANIFOLD_POINTS],
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im2: rb2.effective_inv_mass,
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limit: 0.0,
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mj_lambda2,
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manifold_id,
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manifold_contact_id: [0; MAX_MANIFOLD_POINTS],
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num_contacts: manifold_points.len() as u8,
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};
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// TODO: this is a WIP optimization for WASM platforms.
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// For some reasons, the compiler does not inline the `Vec::push` method
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// in this method. This generates two memset and one memcpy which are both very
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// expansive.
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// This would likely be solved by some kind of "placement-push" (like emplace in C++).
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// In the mean time, a workaround is to "push" using `.resize_with` and `::uninit()` to
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// avoid spurious copying.
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// Is this optimization beneficial when targeting non-WASM platforms?
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//
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// NOTE: joints have the same problem, but it is not easy to refactor the code that way
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// for the moment.
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#[cfg(target_arch = "wasm32")]
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let constraint = if push {
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let new_len = out_constraints.len() + 1;
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unsafe {
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out_constraints.resize_with(new_len, || {
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AnyVelocityConstraint::NongroupedGround(
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std::mem::MaybeUninit::uninit().assume_init(),
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)
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});
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}
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out_constraints
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.last_mut()
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.unwrap()
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.as_nongrouped_ground_mut()
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.unwrap()
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} else {
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unreachable!(); // We don't have parallelization on WASM yet, so this is unreachable.
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};
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#[cfg(target_arch = "wasm32")]
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{
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constraint.dir1 = force_dir1;
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constraint.im2 = rb2.effective_inv_mass;
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constraint.limit = 0.0;
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constraint.mj_lambda2 = mj_lambda2;
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constraint.manifold_id = manifold_id;
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constraint.manifold_contact_id = [0; MAX_MANIFOLD_POINTS];
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constraint.num_contacts = manifold_points.len() as u8;
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}
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for k in 0..manifold_points.len() {
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let manifold_point = &manifold_points[k];
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let dp2 = manifold_point.point - rb2.world_com;
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let dp1 = manifold_point.point - rb1.world_com;
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let vel1 = rb1.linvel + rb1.angvel.gcross(dp1);
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let vel2 = rb2.linvel + rb2.angvel.gcross(dp2);
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constraint.limit = manifold_point.friction;
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constraint.manifold_contact_id[k] = manifold_point.contact_id;
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// Normal part.
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{
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let gcross2 = rb2
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.effective_world_inv_inertia_sqrt
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.transform_vector(dp2.gcross(-force_dir1));
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let r = 1.0 / (rb2.effective_inv_mass + gcross2.gdot(gcross2));
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let is_bouncy = manifold_point.is_bouncy() as u32 as Real;
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let is_resting = 1.0 - is_bouncy;
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let mut rhs = (1.0 + is_bouncy * manifold_point.restitution)
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* (vel1 - vel2).dot(&force_dir1);
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rhs += manifold_point.dist.max(0.0) * inv_dt;
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rhs *= params.velocity_solve_fraction;
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rhs += is_resting * velocity_based_erp_inv_dt * manifold_point.dist.min(0.0);
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constraint.elements[k].normal_part = VelocityGroundConstraintElementPart {
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gcross2,
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rhs,
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impulse: manifold_point.data.impulse * warmstart_coeff,
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r,
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};
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}
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// Tangent parts.
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{
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let tangents1 = force_dir1.orthonormal_basis();
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for j in 0..DIM - 1 {
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let gcross2 = rb2
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.effective_world_inv_inertia_sqrt
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.transform_vector(dp2.gcross(-tangents1[j]));
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let r = 1.0 / (rb2.effective_inv_mass + gcross2.gdot(gcross2));
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let rhs = (vel1 - vel2
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+ flipped_multiplier * manifold_point.tangent_velocity)
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.dot(&tangents1[j]);
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#[cfg(feature = "dim2")]
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let impulse = manifold_points[k].data.tangent_impulse * warmstart_coeff;
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#[cfg(feature = "dim3")]
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let impulse = manifold_points[k].data.tangent_impulse[j] * warmstart_coeff;
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constraint.elements[k].tangent_part[j] =
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VelocityGroundConstraintElementPart {
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gcross2,
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rhs,
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impulse,
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r,
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};
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}
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}
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}
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#[cfg(not(target_arch = "wasm32"))]
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if push {
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out_constraints.push(AnyVelocityConstraint::NongroupedGround(constraint));
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} else {
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out_constraints[manifold.data.constraint_index + _l] =
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AnyVelocityConstraint::NongroupedGround(constraint);
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}
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}
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}
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pub fn warmstart(&self, mj_lambdas: &mut [DeltaVel<Real>]) {
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let mut mj_lambda2 = DeltaVel::zero();
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let tangents1 = self.dir1.orthonormal_basis();
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for i in 0..self.num_contacts as usize {
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let elt = &self.elements[i].normal_part;
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mj_lambda2.linear += self.dir1 * (-self.im2 * elt.impulse);
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mj_lambda2.angular += elt.gcross2 * elt.impulse;
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for j in 0..DIM - 1 {
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let elt = &self.elements[i].tangent_part[j];
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mj_lambda2.linear += tangents1[j] * (-self.im2 * elt.impulse);
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mj_lambda2.angular += elt.gcross2 * elt.impulse;
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}
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}
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mj_lambdas[self.mj_lambda2 as usize].linear += mj_lambda2.linear;
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mj_lambdas[self.mj_lambda2 as usize].angular += mj_lambda2.angular;
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}
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pub fn solve(&mut self, mj_lambdas: &mut [DeltaVel<Real>]) {
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let mut mj_lambda2 = mj_lambdas[self.mj_lambda2 as usize];
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// Solve friction.
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let tangents1 = self.dir1.orthonormal_basis();
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for i in 0..self.num_contacts as usize {
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for j in 0..DIM - 1 {
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let normal_elt = &self.elements[i].normal_part;
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let elt = &mut self.elements[i].tangent_part[j];
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let dimpulse = -tangents1[j].dot(&mj_lambda2.linear)
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+ elt.gcross2.gdot(mj_lambda2.angular)
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+ elt.rhs;
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let limit = self.limit * normal_elt.impulse;
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let new_impulse = (elt.impulse - elt.r * dimpulse).simd_clamp(-limit, limit);
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let dlambda = new_impulse - elt.impulse;
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elt.impulse = new_impulse;
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mj_lambda2.linear += tangents1[j] * (-self.im2 * dlambda);
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mj_lambda2.angular += elt.gcross2 * dlambda;
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}
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}
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// Solve penetration.
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for i in 0..self.num_contacts as usize {
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let elt = &mut self.elements[i].normal_part;
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let dimpulse =
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-self.dir1.dot(&mj_lambda2.linear) + elt.gcross2.gdot(mj_lambda2.angular) + elt.rhs;
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let new_impulse = (elt.impulse - elt.r * dimpulse).max(0.0);
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let dlambda = new_impulse - elt.impulse;
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elt.impulse = new_impulse;
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mj_lambda2.linear += self.dir1 * (-self.im2 * dlambda);
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mj_lambda2.angular += elt.gcross2 * dlambda;
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}
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mj_lambdas[self.mj_lambda2 as usize] = mj_lambda2;
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}
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// FIXME: duplicated code. This is exactly the same as in the non-ground velocity constraint.
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pub fn writeback_impulses(&self, manifolds_all: &mut [&mut ContactManifold]) {
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let manifold = &mut manifolds_all[self.manifold_id];
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for k in 0..self.num_contacts as usize {
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let contact_id = self.manifold_contact_id[k];
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let active_contact = &mut manifold.points[contact_id as usize];
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active_contact.data.impulse = self.elements[k].normal_part.impulse;
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#[cfg(feature = "dim2")]
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{
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active_contact.data.tangent_impulse = self.elements[k].tangent_part[0].impulse;
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}
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#[cfg(feature = "dim3")]
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{
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active_contact.data.tangent_impulse = [
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self.elements[k].tangent_part[0].impulse,
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self.elements[k].tangent_part[1].impulse,
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];
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}
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}
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}
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}
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