263 lines
10 KiB
Rust
263 lines
10 KiB
Rust
use super::{
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AnyVelocityConstraint, DeltaVel, VelocityGroundConstraintElement,
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VelocityGroundConstraintNormalPart,
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};
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use crate::math::{Point, Real, Vector, DIM, MAX_MANIFOLD_POINTS};
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#[cfg(feature = "dim2")]
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use crate::utils::WBasis;
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use crate::utils::{WAngularInertia, WCross, WDot};
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use crate::data::{BundleSet, ComponentSet};
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use crate::dynamics::{IntegrationParameters, RigidBodyIds, RigidBodyMassProps, RigidBodyVelocity};
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use crate::geometry::{ContactManifold, ContactManifoldIndex};
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#[derive(Copy, Clone, Debug)]
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pub(crate) struct VelocityGroundConstraint {
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pub mj_lambda2: usize,
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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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pub im2: Vector<Real>,
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pub limit: Real,
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pub elements: [VelocityGroundConstraintElement<Real>; MAX_MANIFOLD_POINTS],
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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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}
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impl VelocityGroundConstraint {
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pub fn generate<Bodies>(
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params: &IntegrationParameters,
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manifold_id: ContactManifoldIndex,
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manifold: &ContactManifold,
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bodies: &Bodies,
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out_constraints: &mut Vec<AnyVelocityConstraint>,
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push: bool,
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) where
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Bodies: ComponentSet<RigidBodyIds>
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+ ComponentSet<RigidBodyVelocity>
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+ ComponentSet<RigidBodyMassProps>,
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{
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let inv_dt = params.inv_dt();
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let erp_inv_dt = params.erp_inv_dt();
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let mut handle1 = manifold.data.rigid_body1;
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let mut handle2 = manifold.data.rigid_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 handle1, &mut handle2);
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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 (vels1, world_com1) = if let Some(handle1) = handle1 {
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let (vels1, mprops1): (&RigidBodyVelocity, &RigidBodyMassProps) =
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bodies.index_bundle(handle1.0);
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(*vels1, mprops1.world_com)
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} else {
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(RigidBodyVelocity::zero(), Point::origin())
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};
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let (ids2, vels2, mprops2): (&RigidBodyIds, &RigidBodyVelocity, &RigidBodyMassProps) =
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bodies.index_bundle(handle2.unwrap().0);
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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 =
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super::compute_tangent_contact_directions(&force_dir1, &vels1.linvel, &vels2.linvel);
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let mj_lambda2 = ids2.active_set_offset;
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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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#[cfg(feature = "dim3")]
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tangent1: tangents1[0],
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elements: [VelocityGroundConstraintElement::zero(); MAX_MANIFOLD_POINTS],
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im2: mprops2.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: impulse_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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#[cfg(feature = "dim3")]
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{
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constraint.tangent1 = tangents1[0];
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}
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constraint.im2 = mprops2.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 - mprops2.world_com;
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let dp1 = manifold_point.point - world_com1;
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let vel1 = vels1.linvel + vels1.angvel.gcross(dp1);
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let vel2 = vels2.linvel + vels2.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 = mprops2
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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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/ (force_dir1.dot(&mprops2.effective_inv_mass.component_mul(&force_dir1))
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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_wo_bias = (1.0 + is_bouncy * manifold_point.restitution)
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* (vel1 - vel2).dot(&force_dir1);
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rhs_wo_bias +=
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(manifold_point.dist + params.allowed_linear_error).max(0.0) * inv_dt;
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rhs_wo_bias *= is_bouncy + is_resting * params.velocity_solve_fraction;
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let rhs_bias = /* is_resting
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* */ erp_inv_dt
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* (manifold_point.dist + params.allowed_linear_error).min(0.0);
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constraint.elements[k].normal_part = VelocityGroundConstraintNormalPart {
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gcross2,
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rhs: rhs_wo_bias + rhs_bias,
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rhs_wo_bias,
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impulse: 0.0,
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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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constraint.elements[k].tangent_part.impulse = na::zero();
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for j in 0..DIM - 1 {
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let gcross2 = mprops2
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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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/ (tangents1[j]
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.dot(&mprops2.effective_inv_mass.component_mul(&tangents1[j]))
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+ 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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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::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 solve(
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&mut self,
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mj_lambdas: &mut [DeltaVel<Real>],
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solve_normal: bool,
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solve_friction: bool,
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) {
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let mut mj_lambda2 = mj_lambdas[self.mj_lambda2 as usize];
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VelocityGroundConstraintElement::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.im2,
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self.limit,
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&mut mj_lambda2,
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solve_normal,
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solve_friction,
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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.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.elements[k].tangent_part.impulse;
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}
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}
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}
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pub fn remove_bias_from_rhs(&mut self) {
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for elt in &mut self.elements {
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elt.normal_part.rhs = elt.normal_part.rhs_wo_bias;
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}
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}
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}
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