path: root/src/dynamics/solver/velocity_constraint_wide.rs

use super::{AnyVelocityConstraint, DeltaVel};
use crate::dynamics::{IntegrationParameters, RigidBodySet};
use crate::geometry::{ContactManifold, ContactManifoldIndex};
use crate::math::{
    AngVector, AngularInertia, Isometry, Point, SimdFloat, Vector, DIM, MAX_MANIFOLD_POINTS,
    SIMD_WIDTH,
};
use crate::utils::{WAngularInertia, WBasis, WCross, WDot};
use num::Zero;
use simba::simd::{SimdPartialOrd, SimdValue};

#[derive(Copy, Clone, Debug)]
pub(crate) struct WVelocityConstraintElementPart {
    pub gcross1: AngVector<SimdFloat>,
    pub gcross2: AngVector<SimdFloat>,
    pub rhs: SimdFloat,
    pub impulse: SimdFloat,
    pub r: SimdFloat,
}

impl WVelocityConstraintElementPart {
    pub fn zero() -> Self {
        Self {
            gcross1: AngVector::zero(),
            gcross2: AngVector::zero(),
            rhs: SimdFloat::zero(),
            impulse: SimdFloat::zero(),
            r: SimdFloat::zero(),
        }
    }
}

#[derive(Copy, Clone, Debug)]
pub(crate) struct WVelocityConstraintElement {
    pub normal_part: WVelocityConstraintElementPart,
    pub tangent_parts: [WVelocityConstraintElementPart; DIM - 1],
}

impl WVelocityConstraintElement {
    pub fn zero() -> Self {
        Self {
            normal_part: WVelocityConstraintElementPart::zero(),
            tangent_parts: [WVelocityConstraintElementPart::zero(); DIM - 1],
        }
    }
}

#[derive(Copy, Clone, Debug)]
pub(crate) struct WVelocityConstraint {
    pub dir1: Vector<SimdFloat>, // Non-penetration force direction for the first body.
    pub elements: [WVelocityConstraintElement; MAX_MANIFOLD_POINTS],
    pub num_contacts: u8,
    pub im1: SimdFloat,
    pub im2: SimdFloat,
    pub limit: SimdFloat,
    pub mj_lambda1: [usize; SIMD_WIDTH],
    pub mj_lambda2: [usize; SIMD_WIDTH],
    pub manifold_id: [ContactManifoldIndex; SIMD_WIDTH],
    pub manifold_contact_id: usize,
}

impl WVelocityConstraint {
    pub fn generate(
        params: &IntegrationParameters,
        manifold_id: [ContactManifoldIndex; SIMD_WIDTH],
        manifolds: [&ContactManifold; SIMD_WIDTH],
        bodies: &RigidBodySet,
        out_constraints: &mut Vec<AnyVelocityConstraint>,
        push: bool,
    ) {
        let inv_dt = SimdFloat::splat(params.inv_dt());
        let rbs1 = array![|ii| &bodies[manifolds[ii].body_pair.body1]; SIMD_WIDTH];
        let rbs2 = array![|ii| &bodies[manifolds[ii].body_pair.body2]; SIMD_WIDTH];

        let delta1 = Isometry::from(array![|ii| manifolds[ii].delta1; SIMD_WIDTH]);
        let delta2 = Isometry::from(array![|ii| manifolds[ii].delta2; SIMD_WIDTH]);

        let im1 = SimdFloat::from(array![|ii| rbs1[ii].mass_properties.inv_mass; SIMD_WIDTH]);
        let ii1: AngularInertia<SimdFloat> =
            AngularInertia::from(array![|ii| rbs1[ii].world_inv_inertia_sqrt; SIMD_WIDTH]);

        let linvel1 = Vector::from(array![|ii| rbs1[ii].linvel; SIMD_WIDTH]);
        let angvel1 = AngVector::<SimdFloat>::from(array![|ii| rbs1[ii].angvel; SIMD_WIDTH]);

        let pos1 = Isometry::from(array![|ii| rbs1[ii].position; SIMD_WIDTH]);
        let world_com1 = Point::from(array![|ii| rbs1[ii].world_com; SIMD_WIDTH]);

        let im2 = SimdFloat::from(array![|ii| rbs2[ii].mass_properties.inv_mass; SIMD_WIDTH]);
        let ii2: AngularInertia<SimdFloat> =
            AngularInertia::from(array![|ii| rbs2[ii].world_inv_inertia_sqrt; SIMD_WIDTH]);

        let linvel2 = Vector::from(array![|ii| rbs2[ii].linvel; SIMD_WIDTH]);
        let angvel2 = AngVector::<SimdFloat>::from(array![|ii| rbs2[ii].angvel; SIMD_WIDTH]);

        let pos2 = Isometry::from(array![|ii| rbs2[ii].position; SIMD_WIDTH]);
        let world_com2 = Point::from(array![|ii| rbs2[ii].world_com; SIMD_WIDTH]);

        let coll_pos1 = pos1 * delta1;
        let coll_pos2 = pos2 * delta2;

        let force_dir1 = coll_pos1 * -Vector::from(array![|ii| manifolds[ii].local_n1; SIMD_WIDTH]);

        let mj_lambda1 = array![|ii| rbs1[ii].active_set_offset; SIMD_WIDTH];
        let mj_lambda2 = array![|ii| rbs2[ii].active_set_offset; SIMD_WIDTH];

        let friction = SimdFloat::from(array![|ii| manifolds[ii].friction; SIMD_WIDTH]);
        let warmstart_multiplier =
            SimdFloat::from(array![|ii| manifolds[ii].warmstart_multiplier; SIMD_WIDTH]);
        let warmstart_coeff = warmstart_multiplier * SimdFloat::splat(params.warmstart_coeff);

        for l in (0..manifolds[0].num_active_contacts()).step_by(MAX_MANIFOLD_POINTS) {
            let manifold_points = array![|ii| &manifolds[ii].active_contacts()[l..]; SIMD_WIDTH];
            let num_points = manifold_points[0].len().min(MAX_MANIFOLD_POINTS);

            let mut constraint = WVelocityConstraint {
                dir1: force_dir1,
                elements: [WVelocityConstraintElement::zero(); MAX_MANIFOLD_POINTS],
                im1,
                im2,
                limit: friction,
                mj_lambda1,
                mj_lambda2,
                manifold_id,
                manifold_contact_id: l,
                num_contacts: num_points as u8,
            };

            for k in 0..num_points {
                // FIXME: can we avoid the multiplications by coll_pos1/coll_pos2 here?
                // By working as much as possible in local-space.
                let p1 = coll_pos1
                    * Point::from(array![|ii| manifold_points[ii][k].local_p1; SIMD_WIDTH]);
                let p2 = coll_pos2
                    * Point::from(array![|ii| manifold_points[ii][k].local_p2; SIMD_WIDTH]);

                let dist = SimdFloat::from(array![|ii| manifold_points[ii][k].dist; SIMD_WIDTH]);

                let impulse =
                    SimdFloat::from(array![|ii| manifold_points[ii][k].impulse; SIMD_WIDTH]);

                let dp1 = p1 - world_com1;
                let dp2 = p2 - world_com2;

                let vel1 = linvel1 + angvel1.gcross(dp1);
                let vel2 = linvel2 + angvel2.gcross(dp2);

                // Normal part.
                {
                    let gcross1 = ii1.transform_vector(dp1.gcross(force_dir1));
                    let gcross2 = ii2.transform_vector(dp2.gcross(-force_dir1));

                    let r = SimdFloat::splat(1.0)
                        / (im1 + im2 + gcross1.gdot(gcross1) + gcross2.gdot(gcross2));
                    let rhs =
                        (vel1 - vel2).dot(&force_dir1) + dist.simd_max(SimdFloat::zero()) * inv_dt;

                    constraint.elements[k].normal_part = WVelocityConstraintElementPart {
                        gcross1,
                        gcross2,
                        rhs,
                        impulse: impulse * warmstart_coeff,
                        r,
                    };
                }

                // tangent parts.
                let tangents1 =