@three.ez/instanced-mesh/src/utils/SortingUtils.js

Enhanced InstancedMesh with frustum culling, fast raycasting (using BVH), sorting, visibility management and more.

import { radixSort } from 'three/addons/utils/SortUtils.js';
/**
 * Creates a radix sort function specifically for sorting `InstancedMesh2` instances.
 * The sorting is based on the `depth` property of each `InstancedRenderItem`.
 * This function dynamically adjusts for transparent materials by reversing the sort order if necessary.
 * @param target The `InstancedMesh2` 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.depthSort,
        aux: new Array(target._capacity),
        reversed: false
    };
    return function sortFunction(list) {
        options.reversed = !!target.material?.transparent;
        if (target._capacity > options.aux.length) {
            options.aux.length = target._capacity;
        }
        let minZ = Infinity;
        let maxZ = -Infinity;
        for (const { depth } of list) {
            if (depth > maxZ)
                maxZ = depth;
            if (depth < minZ)
                minZ = depth;
        }
        const depthDelta = maxZ - minZ;
        const factor = (2 ** 32 - 1) / depthDelta;
        for (const item of list) {
            item.depthSort = (item.depth - minZ) * factor;
        }
        radixSort(list, options);
    };
}
/** @internal */
export function sortOpaque(a, b) {
    return a.depth - b.depth;
}
/** @internal */
export function sortTransparent(a, b) {
    return b.depth - a.depth;
}
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