pocket-physics/cjs/solve-distance-constraint.js

Verlet physics extracted from pocket-ces demos

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.solveDistanceConstraint = void 0;
const v2_1 = require("./v2");
// negative or zero mass implies a fixed or "pinned" point
function solveDistanceConstraint(p1, p1mass, p2, p2mass, goal, 
// number between 0 and 1
stiffness = 1, 
// If false, correct the previous position in addition to the current position
// when solving the constraint. While unnatural looking, this will prevent
// "energy" (velocity) from being spontaneously created in the constraint
// system.
impartEnergy = true) {
    const mass1 = p1mass > 0 ? p1mass : 1;
    const mass2 = p2mass > 0 ? p2mass : 1;
    const imass1 = 1 / (mass1 || 1);
    const imass2 = 1 / (mass2 || 1);
    const imass = imass1 + imass2;
    // Current relative vector
    const delta = (0, v2_1.sub)((0, v2_1.v2)(), p2.cpos, p1.cpos);
    const deltaMag = (0, v2_1.magnitude)(delta);
    // nothing to do.
    if (deltaMag === 0)
        return;
    // Difference between current distance and goal distance
    const diff = (deltaMag - goal) / deltaMag;
    // TODO: is this even correct? Should mass come into effect here?
    // approximate mass
    (0, v2_1.scale)(delta, delta, diff / imass);
    // TODO: not sure if this is the right place to apply stiffness.
    const p1correction = (0, v2_1.scale)((0, v2_1.v2)(), delta, imass1 * stiffness);
    const p2correction = (0, v2_1.scale)((0, v2_1.v2)(), delta, imass2 * stiffness);
    // Add correction to p1, but only if not "pinned".
    // If it's pinned and p2 is not, apply it to p2.
    if (p1mass > 0) {
        (0, v2_1.add)(p1.cpos, p1.cpos, p1correction);
        if (!impartEnergy)
            (0, v2_1.add)(p1.ppos, p1.ppos, p1correction);
    }
    else if (p2mass > 0) {
        (0, v2_1.sub)(p2.cpos, p2.cpos, p1correction);
        if (!impartEnergy)
            (0, v2_1.sub)(p2.ppos, p2.ppos, p1correction);
    }
    // Add correction to p2, but only if not "pinned".
    // If it's pinned and p1 is not, apply it to p1.
    if (p2mass > 0) {
        (0, v2_1.sub)(p2.cpos, p2.cpos, p2correction);
        if (!impartEnergy)
            (0, v2_1.sub)(p2.ppos, p2.ppos, p2correction);
    }
    else if (p1mass > 0) {
        (0, v2_1.add)(p1.cpos, p1.cpos, p2correction);
        if (!impartEnergy)
            (0, v2_1.add)(p1.ppos, p1.ppos, p2correction);
    }
}
exports.solveDistanceConstraint = solveDistanceConstraint;