gltf-pipeline/lib/updateAccessorComponentTypes.js

Content pipeline tools for optimizing glTF assets.

'use strict';
const Cesium = require('cesium');
const addBuffer = require('./addBuffer');
const ForEach = require('./ForEach');
const readAccessorPacked = require('./readAccessorPacked');

const ComponentDatatype = Cesium.ComponentDatatype;
const WebGLConstants = Cesium.WebGLConstants;

module.exports = updateAccessorComponentTypes;

/**
 * Update accessors referenced by JOINTS_0 and WEIGHTS_0 attributes to use correct component types.
 *
 * @param {Object} gltf A javascript object containing a glTF asset.
 * @returns {Object} The glTF asset with compressed meshes.
 *
 * @private
 */
function updateAccessorComponentTypes(gltf) {
    let componentType;
    ForEach.accessorWithSemantic(gltf, 'JOINTS_0', function(accessorId) {
        const accessor = gltf.accessors[accessorId];
        componentType = accessor.componentType;
        if (componentType === WebGLConstants.BYTE) {
            convertType(gltf, accessor, ComponentDatatype.UNSIGNED_BYTE);
        } else if (componentType !== WebGLConstants.UNSIGNED_BYTE
                && componentType !== WebGLConstants.UNSIGNED_SHORT) {
            convertType(gltf, accessor, ComponentDatatype.UNSIGNED_SHORT);
        }
    });
    ForEach.accessorWithSemantic(gltf, 'WEIGHTS_0', function(accessorId) {
        const accessor = gltf.accessors[accessorId];
        componentType = accessor.componentType;
        if (componentType === WebGLConstants.BYTE) {
            convertType(gltf, accessor, ComponentDatatype.UNSIGNED_BYTE);
        } else if (componentType === WebGLConstants.SHORT) {
            convertType(gltf, accessor, ComponentDatatype.UNSIGNED_SHORT);
        }
    });

    return gltf;
}

function convertType(gltf, accessor, updatedComponentType) {
    const typedArray = ComponentDatatype.createTypedArray(updatedComponentType, readAccessorPacked(gltf, accessor));
    const newBuffer = new Uint8Array(typedArray.buffer);
    accessor.bufferView = addBuffer(gltf, newBuffer);
    accessor.componentType = updatedComponentType;
    accessor.byteOffset = 0;
}