为什么dds文件环境映射是透明的？

Question

我在three.js示例中使用了dds文件的示例，尽管它没有使其透明化，但似乎正在发生。只是幻觉吗？

我尝试了这个dds文件。 envMap▽ https://threejs.org/examples/textures/compressed/Mountains.dds

地图▽ https://threejs.org/examples/textures/compressed/disturb_dxt1_nomip.dds

var loader = new THREE.DDSLoader（）;

        var map1 = loader.load( 'imgs/disturb_dxt1_nomip.dds' );
        map1.minFilter = map1.magFilter = THREE.LinearFilter;
        map1.anisotropy = 4;

        var cubemap1 = loader.load( 'imgs/Mountains.dds', function ( texture ) {
            texture.magFilter = THREE.LinearFilter;
            texture.minFilter = THREE.LinearFilter;
            texture.mapping = THREE.CubeReflectionMapping;
            sphere.material.needsUpdate = true;
        } );

        var geometry = new THREE.SphereBufferGeometry(5, 32, 32);
        geometry.computeVertexNormals();
        sphere = new THREE.Mesh(
            geometry, 
            new THREE.MeshBasicMaterial({
                envMap: cubemap1
            })
        );

        scene.add(sphere);

我不知道为什么结果会这样显示。有人可以解释吗？ https://imgur.com/a/2EG0aCs