pocket-physics/esm/rewind-to-collision-point.js

Verlet physics extracted from pocket-ces demos

import { sub, v2, scale, normalize, add } from "./v2";
import { segmentIntersection } from "./segment-intersection";
const tunnelPoint = v2();
const offset = v2();
const v = v2();
const direction = v2();
const radiusSegment = v2();
const cposIncludingRadius = v2();
export function rewindToCollisionPoint(point3, radius3, point1, point2) {
    // detect if a collision has occurred but would have been missed due to
    // point3 moving beyond the edge in one time step.
    // TODO: this should accept some sort of manifold or collision contact object,
    // not randum args (radius, etc). Without a manifold it's imposible to know 
    // if the point "tunneled" due to a collision or the result of _resolving_
    // a collision!
    // Compute where the cpos would be if the segment actually included the
    // radius.
    // Without this, we would rewind to the point3 center, and the direction
    // of two points colliding with each other exactly is undefined.
    sub(v, point3.cpos, point3.ppos);
    normalize(direction, v);
    scale(radiusSegment, direction, radius3);
    add(cposIncludingRadius, radiusSegment, point3.cpos);
    const hasTunneled = segmentIntersection(cposIncludingRadius, point3.ppos, point1, point2, tunnelPoint);
    if (!hasTunneled)
        return false;
    // Translate point3 to tunnelPoint, including the radius of the point.
    sub(offset, cposIncludingRadius, tunnelPoint);
    sub(point3.cpos, point3.cpos, offset);
    sub(point3.ppos, point3.ppos, offset);
    return true;
}
function debuggerIfNaN(point) {
    if (isNaN(point.x) || isNaN(point.y)) {
        debugger;
    }
}