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;