310 lines
12 KiB
Rust
310 lines
12 KiB
Rust
use super::{AnyVelocityConstraint, DeltaVel};
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use crate::math::{AngVector, 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<f32>,
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pub rhs: f32,
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pub impulse: f32,
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pub r: f32,
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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<f32>, // Non-penetration force direction for the first body.
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pub im2: f32,
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pub limit: f32,
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pub mj_lambda2: usize,
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pub manifold_id: ContactManifoldIndex,
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pub manifold_contact_id: usize,
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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 mut rb1 = &bodies[manifold.body_pair.body1];
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let mut rb2 = &bodies[manifold.body_pair.body2];
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let flipped = !rb2.is_dynamic();
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let force_dir1;
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let coll_pos1;
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let coll_pos2;
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if flipped {
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coll_pos1 = rb2.position * manifold.delta2;
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coll_pos2 = rb1.position * manifold.delta1;
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force_dir1 = coll_pos1 * (-manifold.local_n2);
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std::mem::swap(&mut rb1, &mut rb2);
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} else {
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coll_pos1 = rb1.position * manifold.delta1;
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coll_pos2 = rb2.position * manifold.delta2;
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force_dir1 = coll_pos1 * (-manifold.local_n1);
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}
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let mj_lambda2 = rb2.active_set_offset;
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let warmstart_coeff = manifold.warmstart_multiplier * params.warmstart_coeff;
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for (l, manifold_points) in manifold
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.active_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.mass_properties.inv_mass,
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limit: manifold.friction,
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mj_lambda2,
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manifold_id,
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manifold_contact_id: l * 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.mass_properties.inv_mass;
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constraint.limit = manifold.friction;
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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 = l * 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 (p1, p2) = if flipped {
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// NOTE: we already swapped rb1 and rb2
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// so we multiply by coll_pos1/coll_pos2.
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(
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coll_pos1 * manifold_point.local_p2,
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coll_pos2 * manifold_point.local_p1,
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)
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} else {
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(
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coll_pos1 * manifold_point.local_p1,
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coll_pos2 * manifold_point.local_p2,
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)
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};
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let dp2 = p2 - rb2.world_com;
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let dp1 = p1 - 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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// Normal part.
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{
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let gcross2 = rb2
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.world_inv_inertia_sqrt
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.transform_vector(dp2.gcross(-force_dir1));
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let r = 1.0 / (rb2.mass_properties.inv_mass + gcross2.gdot(gcross2));
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let mut rhs = (vel1 - vel2).dot(&force_dir1);
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if rhs <= -params.restitution_velocity_threshold {
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rhs += manifold.restitution * rhs
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}
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rhs += manifold_point.dist.max(0.0) * inv_dt;
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let impulse = manifold_points[k].impulse * warmstart_coeff;
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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,
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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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.world_inv_inertia_sqrt
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.transform_vector(dp2.gcross(-tangents1[j]));
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let r = 1.0 / (rb2.mass_properties.inv_mass + gcross2.gdot(gcross2));
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let rhs = -vel2.dot(&tangents1[j]) + vel1.dot(&tangents1[j]);
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#[cfg(feature = "dim2")]
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let impulse = manifold_points[k].tangent_impulse * warmstart_coeff;
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#[cfg(feature = "dim3")]
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let impulse = manifold_points[k].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.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<f32>]) {
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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<f32>]) {
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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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let k_base = self.manifold_contact_id;
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for k in 0..self.num_contacts as usize {
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let active_contacts = manifold.active_contacts_mut();
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active_contacts[k_base + k].impulse = self.elements[k].normal_part.impulse;
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#[cfg(feature = "dim2")]
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{
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active_contacts[k_base + k].tangent_impulse =
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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_contacts[k_base + k].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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