@three.ez/batched-mesh-extensions/src/utils/SortingUtils.js

Utility extension methods for BatchedMesh

import { radixSort } from 'three/addons/utils/SortUtils.js';
/**
 * Creates a radix sort function specifically for sorting `BatchedMesh` instances.
 * The sorting is based on the `depth` property of each `MultiDrawRenderItem`.
 * This function dynamically adjusts for transparent materials by reversing the sort order if necessary.
 * @param target The `BatchedMesh` instance that contains the instances to be sorted.
 * @returns A radix sort function.
 * @reference https://github.com/mrdoob/three.js/blob/master/examples/webgl_mesh_batch.html#L291
 */
export function createRadixSort(target) {
    const options = {
        get: (el) => el.zSort,
        aux: new Array(target.maxInstanceCount),
        reversed: null
    };
    return function sortFunction(list) {
        options.reversed = target.material.transparent;
        if (target.maxInstanceCount > options.aux.length) {
            options.aux.length = target.maxInstanceCount;
        }
        let minZ = Infinity;
        let maxZ = -Infinity;
        for (const { z } of list) {
            if (z > maxZ)
                maxZ = z;
            if (z < minZ)
                minZ = z;
        }
        const depthDelta = maxZ - minZ;
        const factor = (2 ** 32 - 1) / depthDelta;
        for (const item of list) {
            item.zSort = (item.z - minZ) * factor;
        }
        radixSort(list, options);
    };
}
/** @internal */
export function sortOpaque(a, b) {
    return a.z - b.z;
}
/** @internal */
export function sortTransparent(a, b) {
    return b.z - a.z;
}
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