cesium/Source/ThirdParty/GltfPipeline/updateAccessorComponentTypes.js

CesiumJS is a JavaScript library for creating 3D globes and 2D maps in a web browser without a plugin.

import addBuffer from './addBuffer.js'
import ForEach from './ForEach.js'
import readAccessorPacked from './readAccessorPacked.js'
import ComponentDatatype from '../../Core/ComponentDatatype.js'
import WebGLConstants from '../../Core/WebGLConstants.js'

    /**
     * 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) {
        var componentType;
        ForEach.accessorWithSemantic(gltf, 'JOINTS_0', function(accessorId) {
            var 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) {
            var 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) {
        var typedArray = ComponentDatatype.createTypedArray(updatedComponentType, readAccessorPacked(gltf, accessor));
        var newBuffer = new Uint8Array(typedArray.buffer);
        accessor.bufferView = addBuffer(gltf, newBuffer);
        accessor.componentType = updatedComponentType;
        accessor.byteOffset = 0;
    }

    export default updateAccessorComponentTypes;