H5+Canvas渐变背景效果

代码片段：

uniforms: {
    uResolution: function uResolution(_ref2) {
      var viewportWidth = _ref2.viewportWidth;
      var viewportHeight = _ref2.viewportHeight;
      return [viewportWidth, viewportHeight];
    },
    uTime: function uTime(_ref3) {
      var tick = _ref3.tick;
      return 0.01 * tick;
    },
    uMouse: function uMouse() {
      return [pointer.position.x, pointer.position.y];
    },
    uMorph: function uMorph() {
      return morphAmount;
    },
    uRandomSeed: DEV ? 138975.579831 : new Date().getTime() % 1000000, //
    uGrid: function uGrid(_ref4) {
      var viewportWidth = _ref4.viewportWidth;
      var viewportHeight = _ref4.viewportHeight;

      var ratio = 0.32;
      return viewportHeight >= viewportWidth ? [1, viewportHeight / viewportWidth * ratio] : [viewportWidth / viewportHeight * ratio, 1];
    }
  },