@woosh/meep-engine/src/engine/graphics/geometry/buffered/buffer_attribute_deinterleave.js

Pure JavaScript game engine. Fully featured and production ready.

import { BufferAttribute } from "three";


/**
 *
 * @param {THREE.InterleavedBufferAttribute|THREE.BufferAttribute} source_attribute
 * @returns {THREE.BufferAttribute}
 */
export function buffer_attribute_deinterleave(source_attribute) {
    if (source_attribute.isInterleavedBufferAttribute !== true && source_attribute.isBufferAttribute) {
        // already isn't interleaved
        return source_attribute;
    }

    const source_data = source_attribute.data;
    const source_data_array = source_data.array;
    const stride = source_data.stride;

    const item_count = source_attribute.count;
    const itemSize = source_attribute.itemSize;
    const array_size = item_count * itemSize;

    const offset = source_attribute.offset;

    const destination_array = new source_data_array.constructor(array_size);

    const attribute = new BufferAttribute(destination_array, itemSize);

    attribute.normalized = source_attribute.normalized;
    attribute.name = source_attribute.name;

    let i = 0, j = 0;
    // copy data
    for (; i < item_count; i++) {
        for (j = 0; j < itemSize; j++) {
            destination_array[i * itemSize + j] = source_data_array[i * stride + offset + j];
        }
    }

    return attribute;
}