@woosh/meep-engine/src/engine/graphics/geometry/MikkT/QuickSortEdges.js

Pure JavaScript game engine. Fully featured and production ready.

import { array_swap } from "../../../../core/collection/array/array_swap.js";
import { assert } from "../../../../core/assert.js";

/**
 *
 * @param {number[]} pSortBuffer
 * @param {number} iLeft
 * @param {number} iRight
 * @param {number} channel
 * @param {number} uSeed
 * @returns {void}
 */
export function QuickSortEdges(pSortBuffer, iLeft, iRight, channel, uSeed) {
    let t;
    let iL, iR, n, index, iMid;

    // early out
    const iElems = iRight - iLeft + 1;

    if (iElems < 2) {
        return;
    } else if (iElems === 2) {

        if (pSortBuffer[iLeft * 3 + channel] > pSortBuffer[iRight * 3 + channel]) {

            array_swap(pSortBuffer, iLeft * 3, pSortBuffer, iRight * 3, 3); // swap elements

        }

        return;
    }

    // Random
    t = uSeed & 31;
    t = (uSeed << t) | (uSeed >> (32 - t));
    uSeed = uSeed + t + 3;

    uSeed = uSeed >>> 0; // make unsigned
    // Random end

    iL = iLeft;
    iR = iRight;
    n = (iR - iL) + 1;

    assert.greaterThanOrEqual(n, 0);

    index = (uSeed % n);

    iMid = pSortBuffer[(index + iL) * 3 + channel];

    do {
        while (pSortBuffer[iL * 3 + channel] < iMid)
            ++iL;
        while (pSortBuffer[iR * 3 + channel] > iMid)
            --iR;

        if (iL <= iR) {

            array_swap(pSortBuffer, iL * 3, pSortBuffer, iR * 3, 3); // do swap

            ++iL;
            --iR;
        }
    }
    while (iL <= iR);

    if (iLeft < iR)
        QuickSortEdges(pSortBuffer, iLeft, iR, channel, uSeed);
    if (iL < iRight)
        QuickSortEdges(pSortBuffer, iL, iRight, channel, uSeed);
}