392 lines
16 KiB
Rust
392 lines
16 KiB
Rust
use crate::dynamics::solver::VelocityGroundConstraint;
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#[cfg(feature = "simd-is-enabled")]
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use crate::dynamics::solver::{WVelocityConstraint, WVelocityGroundConstraint};
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use crate::dynamics::{IntegrationParameters, RigidBodySet};
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use crate::geometry::{ContactManifold, ContactManifoldIndex};
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use crate::math::{Real, Vector, DIM, MAX_MANIFOLD_POINTS};
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use crate::utils::{WAngularInertia, WBasis, WCross, WDot};
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use super::{DeltaVel, VelocityConstraintElement, VelocityConstraintNormalPart};
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//#[repr(align(64))]
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#[derive(Copy, Clone, Debug)]
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pub(crate) enum AnyVelocityConstraint {
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NongroupedGround(VelocityGroundConstraint),
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Nongrouped(VelocityConstraint),
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#[cfg(feature = "simd-is-enabled")]
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GroupedGround(WVelocityGroundConstraint),
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#[cfg(feature = "simd-is-enabled")]
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Grouped(WVelocityConstraint),
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#[allow(dead_code)] // The Empty variant is only used with parallel code.
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Empty,
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}
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impl AnyVelocityConstraint {
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#[cfg(target_arch = "wasm32")]
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pub fn as_nongrouped_mut(&mut self) -> Option<&mut VelocityConstraint> {
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if let AnyVelocityConstraint::Nongrouped(c) = self {
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Some(c)
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} else {
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None
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}
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}
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#[cfg(target_arch = "wasm32")]
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pub fn as_nongrouped_ground_mut(&mut self) -> Option<&mut VelocityGroundConstraint> {
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if let AnyVelocityConstraint::NongroupedGround(c) = self {
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Some(c)
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} else {
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None
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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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match self {
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AnyVelocityConstraint::NongroupedGround(c) => c.warmstart(mj_lambdas),
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AnyVelocityConstraint::Nongrouped(c) => c.warmstart(mj_lambdas),
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#[cfg(feature = "simd-is-enabled")]
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AnyVelocityConstraint::GroupedGround(c) => c.warmstart(mj_lambdas),
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#[cfg(feature = "simd-is-enabled")]
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AnyVelocityConstraint::Grouped(c) => c.warmstart(mj_lambdas),
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AnyVelocityConstraint::Empty => unreachable!(),
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}
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}
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pub fn solve(&mut self, mj_lambdas: &mut [DeltaVel<Real>]) {
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match self {
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AnyVelocityConstraint::NongroupedGround(c) => c.solve(mj_lambdas),
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AnyVelocityConstraint::Nongrouped(c) => c.solve(mj_lambdas),
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#[cfg(feature = "simd-is-enabled")]
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AnyVelocityConstraint::GroupedGround(c) => c.solve(mj_lambdas),
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#[cfg(feature = "simd-is-enabled")]
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AnyVelocityConstraint::Grouped(c) => c.solve(mj_lambdas),
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AnyVelocityConstraint::Empty => unreachable!(),
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}
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}
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pub fn writeback_impulses(&self, manifold_all: &mut [&mut ContactManifold]) {
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match self {
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AnyVelocityConstraint::NongroupedGround(c) => c.writeback_impulses(manifold_all),
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AnyVelocityConstraint::Nongrouped(c) => c.writeback_impulses(manifold_all),
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#[cfg(feature = "simd-is-enabled")]
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AnyVelocityConstraint::GroupedGround(c) => c.writeback_impulses(manifold_all),
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#[cfg(feature = "simd-is-enabled")]
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AnyVelocityConstraint::Grouped(c) => c.writeback_impulses(manifold_all),
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AnyVelocityConstraint::Empty => unreachable!(),
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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 VelocityConstraint {
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pub dir1: Vector<Real>, // Non-penetration force direction for the first body.
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#[cfg(feature = "dim3")]
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pub tangent1: Vector<Real>, // One of the friction force directions.
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#[cfg(feature = "dim3")]
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pub tangent_rot1: na::UnitComplex<Real>, // Orientation of the tangent basis wrt. the reference basis.
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pub im1: Real,
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pub im2: Real,
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pub limit: Real,
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pub mj_lambda1: usize,
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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: [VelocityConstraintElement<Real>; MAX_MANIFOLD_POINTS],
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}
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impl VelocityConstraint {
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#[cfg(feature = "parallel")]
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pub fn num_active_constraints(manifold: &ContactManifold) -> usize {
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let rest = manifold.data.solver_contacts.len() % MAX_MANIFOLD_POINTS != 0;
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manifold.data.solver_contacts.len() / MAX_MANIFOLD_POINTS + rest as usize
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}
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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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assert_eq!(manifold.data.relative_dominance, 0);
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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 rb1 = &bodies[manifold.data.body_pair.body1];
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let rb2 = &bodies[manifold.data.body_pair.body2];
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let mj_lambda1 = rb1.active_set_offset;
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let mj_lambda2 = rb2.active_set_offset;
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let force_dir1 = -manifold.data.normal;
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let warmstart_coeff = manifold.data.warmstart_multiplier * params.warmstart_coeff;
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#[cfg(feature = "dim2")]
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let tangents1 = force_dir1.orthonormal_basis();
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#[cfg(feature = "dim3")]
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let (tangents1, tangent_rot1) =
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super::compute_tangent_contact_directions(&force_dir1, &rb1.linvel, &rb2.linvel);
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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 = VelocityConstraint {
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dir1: force_dir1,
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#[cfg(feature = "dim3")]
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tangent1: tangents1[0],
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#[cfg(feature = "dim3")]
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tangent_rot1,
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elements: [VelocityConstraintElement::zero(); MAX_MANIFOLD_POINTS],
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im1: rb1.effective_inv_mass,
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im2: rb2.effective_inv_mass,
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limit: 0.0,
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mj_lambda1,
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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::Nongrouped(
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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_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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#[cfg(feature = "dim3")]
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{
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constraint.tangent1 = tangents1[0];
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constraint.tangent_rot1 = tangent_rot1;
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}
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constraint.im1 = rb1.effective_inv_mass;
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constraint.im2 = rb2.effective_inv_mass;
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constraint.limit = 0.0;
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constraint.mj_lambda1 = mj_lambda1;
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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 dp1 = manifold_point.point - rb1.world_com;
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let dp2 = manifold_point.point - rb2.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 gcross1 = rb1
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.effective_world_inv_inertia_sqrt
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.transform_vector(dp1.gcross(force_dir1));
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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
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/ (rb1.effective_inv_mass
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+ rb2.effective_inv_mass
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+ gcross1.gdot(gcross1)
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+ 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 *= is_bouncy + is_resting * 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 = VelocityConstraintNormalPart {
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gcross1,
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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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#[cfg(feature = "dim3")]
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let impulse =
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tangent_rot1 * manifold_points[k].data.tangent_impulse * warmstart_coeff;
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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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constraint.elements[k].tangent_part.impulse = impulse;
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for j in 0..DIM - 1 {
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let gcross1 = rb1
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.effective_world_inv_inertia_sqrt
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.transform_vector(dp1.gcross(tangents1[j]));
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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
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/ (rb1.effective_inv_mass
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+ rb2.effective_inv_mass
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+ gcross1.gdot(gcross1)
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+ gcross2.gdot(gcross2));
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let rhs =
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(vel1 - vel2 + manifold_point.tangent_velocity).dot(&tangents1[j]);
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constraint.elements[k].tangent_part.gcross1[j] = gcross1;
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constraint.elements[k].tangent_part.gcross2[j] = gcross2;
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constraint.elements[k].tangent_part.rhs[j] = rhs;
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constraint.elements[k].tangent_part.r[j] = r;
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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::Nongrouped(constraint));
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} else {
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out_constraints[manifold.data.constraint_index + _l] =
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AnyVelocityConstraint::Nongrouped(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_lambda1 = DeltaVel::zero();
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let mut mj_lambda2 = DeltaVel::zero();
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VelocityConstraintElement::warmstart_group(
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&self.elements[..self.num_contacts as usize],
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&self.dir1,
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#[cfg(feature = "dim3")]
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&self.tangent1,
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self.im1,
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self.im2,
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&mut mj_lambda1,
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&mut mj_lambda2,
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);
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mj_lambdas[self.mj_lambda1 as usize] += mj_lambda1;
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mj_lambdas[self.mj_lambda2 as usize] += mj_lambda2;
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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_lambda1 = mj_lambdas[self.mj_lambda1 as usize];
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let mut mj_lambda2 = mj_lambdas[self.mj_lambda2 as usize];
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VelocityConstraintElement::solve_group(
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&mut self.elements[..self.num_contacts as usize],
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&self.dir1,
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#[cfg(feature = "dim3")]
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&self.tangent1,
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self.im1,
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self.im2,
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self.limit,
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&mut mj_lambda1,
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&mut mj_lambda2,
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);
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mj_lambdas[self.mj_lambda1 as usize] = mj_lambda1;
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mj_lambdas[self.mj_lambda2 as usize] = mj_lambda2;
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}
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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.impulse[0];
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}
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#[cfg(feature = "dim3")]
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{
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active_contact.data.tangent_impulse = self
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.tangent_rot1
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.inverse_transform_vector(&self.elements[k].tangent_part.impulse);
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}
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}
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}
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}
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#[inline(always)]
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#[cfg(feature = "dim3")]
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pub(crate) fn compute_tangent_contact_directions<N>(
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force_dir1: &Vector<N>,
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linvel1: &Vector<N>,
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linvel2: &Vector<N>,
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) -> ([Vector<N>; DIM - 1], na::UnitComplex<N>)
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where
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N: na::SimdRealField,
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N::Element: na::RealField,
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Vector<N>: WBasis,
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{
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use na::SimdValue;
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// Compute the tangent direction. Pick the direction of
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// the linear relative velocity, if it is not too small.
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// Otherwise use a fallback direction.
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let relative_linvel = linvel1 - linvel2;
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let mut tangent_relative_linvel =
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relative_linvel - force_dir1 * (force_dir1.dot(&relative_linvel));
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let tangent_linvel_norm = tangent_relative_linvel.normalize_mut();
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let threshold: N::Element = na::convert(1.0e-4);
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let use_fallback = tangent_linvel_norm.simd_lt(N::splat(threshold));
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let tangent_fallback = force_dir1.orthonormal_vector();
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let tangent1 = tangent_fallback.select(use_fallback, tangent_relative_linvel);
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let bitangent1 = force_dir1.cross(&tangent1);
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// Rotation such that: rot * tangent_fallback = tangent1
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// (when projected in the tangent plane.) This is needed to ensure the
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// warmstart impulse has the correct orientation. Indeed, at frame n + 1,
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// we need to reapply the same impulse as we did in frame n. However the
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// basis on which the tangent impulse is expresses may change at each frame
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// (because the the relative linvel may change direction at each frame).
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// So we need this rotation to:
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// - Project the impulse back to the "reference" basis at after friction is resolved.
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// - Project the old impulse on the new basis before the friction is resolved.
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let rot = na::UnitComplex::new_unchecked(na::Complex::new(
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tangent1.dot(&tangent_fallback),
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bitangent1.dot(&tangent_fallback),
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));
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([tangent1, bitangent1], rot)
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}
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