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   源码介绍

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cesium实现光圈渲染, Cesium.Viewer

  Cesium.defineProperties(EllipsoidFadeMaterialProperty.prototype, {
        isConstant: {
            get: function () {
                return false
            }
        },
        definitionChanged: {
            get: function () {
                return this._definitionChanged
            }
        },
        color: Cesium.createPropertyDescriptor('color')
    });
    EllipsoidFadeMaterialProperty.prototype.getType = function (time) {
        return 'EllipsoidFade';
    }
    EllipsoidFadeMaterialProperty.prototype.getValue = function (time, result) {
        if (!Cesium.defined(result)) {
            result = {};
        }
        result.color = Cesium.Property.getValueOrClonedDefault(this._color, time, Cesium.Color.WHITE, result.color);
        result.time = ((new Date().getTime() - this._time) % this.duration) / this.duration;
        return result;
    }
    EllipsoidFadeMaterialProperty.prototype.equals = function (other) {
        return this === other ||
            (other instanceof EllipsoidFadeMaterialProperty && Property.equals(this._color, other._color))
    }
    Cesium.EllipsoidFadeMaterialProperty = EllipsoidFadeMaterialProperty;

    Cesium.Material.EllipsoidFadeType = "EllipsoidFade";
    // 自定义着色器
    Cesium.Material.EllipsoidFadeSource =
        "czm_material czm_getMaterial(czm_materialInput materialInput)\n"
        "{\n"
        "  czm_material material = czm_getDefaultMaterial(materialInput);\n"
        "  material.diffuse = 1.5 * color.rgb;\n"
        "  vec2 st = materialInput.st;\n"
        "  float dis = distance(st, vec2(0.5, 0.5));\n"
        "  float per = fract(time);\n"
        "  if(dis > per * 0.5) {\n"
        "    material.alpha = 0.0;\n"
        "    discard;\n"
        "  }else{\n"
        "    material.alpha = color.a * dis / per / 1.0;\n"
        "  }\n"
        "  return material;\n"
        "}";
    Cesium.Material._materialCache.addMaterial(Cesium.Material.EllipsoidFadeType, {
        fabric: {
            type: Cesium.Material.EllipsoidFadeType,
            uniforms: {
                color: new Cesium.Color(1.0, 0.0, 0.0, 1),
                time: 0
            },
            source: Cesium.Material.EllipsoidFadeSource

        },
        translucent: function (material) {
            return true;
        }

    })

  viewer.entities.add({
        name: 'EllipsoidFade',
        position: Cesium.Cartesian3.fromDegrees(x, y, 0),
        ellipse: {
            height: 0,
            semiMinorAxis: new Cesium.CallbackProperty(changeR1, false),
            semiMajorAxis: new Cesium.CallbackProperty(changeR1, false),
            material: new Cesium.EllipsoidFadeMaterialProperty(color, 2000)
        }
    });

var minR = 1000;
var maxR = 9000;
var r1 = 1000;
function changeR1() { //这是callback，参数不能内传
    r1 ;
    if (r1 >= maxR) {
        r1 = minR;
    }

    return r1;
}

function EllipsoidFadeMaterialProperty(color, duration) {
    this._definitionChanged = new Cesium.Event();
    this._color = undefined;
    this._colorSubscription = undefined;
    this.color = color;
    this.duration = duration;
    this._time = (new Date()).getTime();
}