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    <head>
        <title>three.js webgl - animation - groups</title>
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        <div id="info">
            <a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> webgl - animation - groups
        </div>
        <script type="importmap">
            {
                "imports": {
                    "three": "./three-js-master/build/three.module.js",
                    "three/addons/": "./three-js-master/examples/jsm/"
                }
            }
        </script>
        <script type="module">
            import * as THREE from 'three';
            import Stats from 'three/addons/libs/stats.module.js';
            let stats, clock;
            let scene, camera, renderer, mixer;
            init();
            function init() {
                scene = new THREE.Scene();
                //
                camera = new THREE.PerspectiveCamera( 40, window.innerWidth / window.innerHeight, 1, 1000 );
                camera.position.set( 50, 50, 100 );
                camera.lookAt( scene.position );
                // all objects of this animation group share a common animation state
                const animationGroup = new THREE.AnimationObjectGroup();
                //
                const geometry = new THREE.BoxGeometry( 5, 5, 5 );
                const material = new THREE.MeshBasicMaterial( { transparent: true } );
                //
                for ( let i = 0; i < 5; i ++ ) {
                    for ( let j = 0; j < 5; j ++ ) {
                        const mesh = new THREE.Mesh( geometry, material );
                        mesh.position.x = 32 - ( 16 * i );
                        mesh.position.y = 0;
                        mesh.position.z = 32 - ( 16 * j );
                        scene.add( mesh );
                        animationGroup.add( mesh );
                    }
                }
                // create some keyframe tracks
                const xAxis = new THREE.Vector3( 1, 0, 0 );
                const qInitial = new THREE.Quaternion().setFromAxisAngle( xAxis, 0 );
                const qFinal = new THREE.Quaternion().setFromAxisAngle( xAxis, Math.PI );
                const quaternionKF = new THREE.QuaternionKeyframeTrack( '.quaternion', [ 0, 1, 2 ], [ qInitial.x, qInitial.y, qInitial.z, qInitial.w, qFinal.x, qFinal.y, qFinal.z, qFinal.w, qInitial.x, qInitial.y, qInitial.z, qInitial.w ] );
                const colorKF = new THREE.ColorKeyframeTrack( '.material.color', [ 0, 1, 2 ], [ 1, 0, 0, 0, 1, 0, 0, 0, 1 ], THREE.InterpolateDiscrete );
                const opacityKF = new THREE.NumberKeyframeTrack( '.material.opacity', [ 0, 1, 2 ], [ 1, 0, 1 ] );
                // create clip
                const clip = new THREE.AnimationClip( 'default', 3, [ quaternionKF, colorKF, opacityKF ] );
                // apply the animation group to the mixer as the root object
                mixer = new THREE.AnimationMixer( animationGroup );
                const clipAction = mixer.clipAction( clip );
                clipAction.play();
                //
                renderer = new THREE.WebGLRenderer( { antialias: true } );
                renderer.setPixelRatio( window.devicePixelRatio );
                renderer.setSize( window.innerWidth, window.innerHeight );
                renderer.setAnimationLoop( animate );
                document.body.appendChild( renderer.domElement );
                //
                stats = new Stats();
                document.body.appendChild( stats.dom );
                //
                clock = new THREE.Clock();
                //
                window.addEventListener( 'resize', onWindowResize );
            }
            function onWindowResize() {
                camera.aspect = window.innerWidth / window.innerHeight;
                camera.updateProjectionMatrix();
                renderer.setSize( window.innerWidth, window.innerHeight );
            }
            function animate() {
                const delta = clock.getDelta();
                if ( mixer ) {
                    mixer.update( delta );
                }
                renderer.render( scene, camera );
                stats.update();
            }
        </script>
    </body>
</html>