sdk4.0/src/Obj/Materail/PolylineFlowMaterialProperty.js

/*
 * @Description: 流动线
 */
function PolylineFlow() {
  class PolylineFlowMaterialProperty {
    constructor(options) {
      this._definitionChanged = new Cesium.Event();
      this._color = undefined;
      this._speed = undefined;
      this._rotate = undefined;
      this.color = new Cesium.Color.fromCssColorString(options.color || "rgba(255,255,255,1)");
      this.speed = options.speed != undefined ? options.speed : 1.0;//速度
      this.lineBackAlpha = options.lineBackAlpha || 0.05;
      this.rotate = options.rotate;
    }

    get isConstant() {
      return false;
    }

    get definitionChanged() {
      return this._definitionChanged;
    }

    getType(time) {
      return Cesium.Material.PolylineFlowMaterialType;
    }

    getValue(time, result) {
      if (!Cesium.defined(result)) {
        result = {};
      }

      result.color = Cesium.Property.getValueOrDefault(
        this._color,
        time,
        Cesium.Color.RED,
        result.color
      );
      result.speed = Cesium.Property.getValueOrDefault(
        this._speed,
        time,
        10,
        result.speed
      );
      result.rotate = Cesium.Property.getValueOrDefault(
        this._rotate,
        time,
        true,
        result.rotate
      );
      result.lineBackAlpha = this.lineBackAlpha;
      result.frameTime = Cesium.getTimestamp();
      // result.frameNumber = Cesium.getTimestamp();
      return result;
    }

    equals(other) {
      return (
        this === other ||
        (other instanceof PolylineFlowMaterialProperty &&
          Cesium.Property.equals(this._color, other._color) &&
          Cesium.Property.equals(this._speed, other.speed) &&
          Cesium.Property.equals(this.lineBackAlpha, other.lineBackAlpha))
      );
    }
  }

  Object.defineProperties(PolylineFlowMaterialProperty.prototype, {
    color: Cesium.createPropertyDescriptor("color"),
    speed: Cesium.createPropertyDescriptor("speed"),
    rotate: Cesium.createPropertyDescriptor("rotate"),
    transparency: Cesium.createPropertyDescriptor("lineBackAlpha"),
  });

  Cesium.PolylineFlowMaterialProperty = PolylineFlowMaterialProperty;
  Cesium.Material.PolylineFlowMaterialProperty = "PolylineFlowMaterialProperty";
  Cesium.Material.PolylineFlowMaterialType = "PolylineFlowMaterialType";
  Cesium.Material.PolylineFlowMaterialSource = `
      uniform vec4 color;
      uniform float speed;
      uniform float lineBackAlpha;

      czm_material czm_getMaterial(czm_materialInput materialInput)
        {
            //生成默认的基础材质
            czm_material material = czm_getDefaultMaterial(materialInput);
            //获取st（uv）
            vec2 st = materialInput.st;
            //获取当前帧数，10秒内变化0-1
            // float time = fract(czm_frameNumber * speed / 60.0);
            // float time = fract(abs(speed) * czm_frameNumber * 0.01);
            float time = fract(frameTime / 1000.0  / abs(speed));
            //长度1/10
            // time = time * (1.0 + 0.1);
            float staticAlpha = rotate?smoothstep(0.0,1.0, 1.0-st.s) * step(-1.0,-(1.0-st.s)):smoothstep(0.0,1.0, st.s) * step(-1.0,-st.s);

            //平滑过渡函数
            float alpha1 = smoothstep(time-0.1,time,1.0-st.s) * step(-time,- (1.0-st.s));
            float alpha2 = smoothstep(time-0.1,time,st.s) * step(-time,- st.s);
            float alpha =(speed== 0.0)? staticAlpha:(speed < 0.0)?alpha2:alpha1;
            //光带轨迹（不会完全透明）
            alpha += lineBackAlpha;
            material.alpha = alpha;
            material.diffuse = color.rgb;
            return material;
        }
       `;

  Cesium.Material._materialCache.addMaterial(
    Cesium.Material.PolylineFlowMaterialType,
    {
      fabric: {
        type: Cesium.Material.PolylineFlowMaterialType,
        uniforms: {
          color: new Cesium.Color(1.0, 1.0, 1.0, 1.0),
          speed: 0.1,
          rotate: true,
          frameTime: Cesium.getTimestamp(),
          lineBackAlpha: 0.05,
        },
        source: Cesium.Material.PolylineFlowMaterialSource,
      },
      translucent: function (material) {
        return true;
      },
    }
  );
}

export { PolylineFlow }