Entity 和primitive 对比

Entity 和primitive 对比

1. entity偏向数据,primitive偏向图形.primitive更底层
2. entity用法简单，primitive用法复杂。我们会有这样的疑问：entity已经封装的如此完美，调用如此便捷，为何还要primitive接口呢？区别就是加载效率。primitive更接近webgl底层，没有entity各种各样的附加属性，因此在加载时效率会更高。

Entity

 for (let index = 0; index < 1000; index++) {
        viewer.entities.add({
            position: new Cesium.Cartesian3.fromDegrees(Math.random() * 100, Math.random() * 100, 10000),
            ellipse: {
                semiMinorAxis: 10000.0,
                semiMajorAxis: 10000.0,
                material: Cesium.Color.RED
            }
        });
    }

Primitive

 var instances = [];
    for (let index = 0; index < 1000; index++) {
        var ellipse = new Cesium.EllipseGeometry({
            center: new Cesium.Cartesian3.fromDegrees(Math.random() * 100, Math.random() * 100),
            semiMajorAxis: 10000.0,
            semiMinorAxis: 10000.0,
        });
        var geometry = Cesium.EllipseGeometry.createGeometry(ellipse);
        var ellipseInstance = new Cesium.GeometryInstance({
            geometry: geometry,
            attributes: {
                color: Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.RED)
            }
        });

        instances.push(ellipseInstance);
    }
    viewer.scene.primitives.add(new Cesium.Primitive({
        geometryInstances: instances,
        appearance: new Cesium.PerInstanceColorAppearance(),
        asynchronous: false,
    }));