gltf-pipeline/lib/readAccessorPacked.js

Content pipeline tools for optimizing glTF assets.

'use strict';
const Cesium = require('cesium');
const getAccessorByteStride = require('./getAccessorByteStride');
const getComponentReader = require('./getComponentReader');
const numberOfComponentsForType = require('./numberOfComponentsForType');

const arrayFill = Cesium.arrayFill;
const ComponentDatatype = Cesium.ComponentDatatype;
const defined = Cesium.defined;

module.exports = readAccessorPacked;

/**
 * Returns the accessor data in a contiguous array.
 *
 * @param {Object} gltf A javascript object containing a glTF asset.
 * @param {Object} accessor The accessor.
 * @returns {Array} The accessor values in a contiguous array.
 *
 * @private
 */
function readAccessorPacked(gltf, accessor) {
    const byteStride = getAccessorByteStride(gltf, accessor);
    const componentTypeByteLength = ComponentDatatype.getSizeInBytes(accessor.componentType);
    const numberOfComponents = numberOfComponentsForType(accessor.type);
    const count = accessor.count;
    const values = new Array(numberOfComponents * count);

    if (!defined(accessor.bufferView)) {
        arrayFill(values, 0);
        return values;
    }

    const bufferView = gltf.bufferViews[accessor.bufferView];
    const source = gltf.buffers[bufferView.buffer].extras._pipeline.source;
    let byteOffset = accessor.byteOffset + bufferView.byteOffset + source.byteOffset;

    const dataView = new DataView(source.buffer);
    const components = new Array(numberOfComponents);
    const componentReader = getComponentReader(accessor.componentType);

    for (let i = 0; i < count; ++i) {
        componentReader(dataView, byteOffset, numberOfComponents, componentTypeByteLength, components);
        for (let j = 0; j < numberOfComponents; ++j) {
            values[i * numberOfComponents + j] = components[j];
        }
        byteOffset += byteStride;
    }
    return values;
}