CSS 动画 - 请告诉我为什么案例 #1 有效，但案例 #2 无效

Question

动画 正在应用的动画是一个 CSS“模糊”，它应该在向下滚动时模糊元素，然后在向上滚动时将其重新聚焦。

示例 #1 - 有效！ HTML 和 CSS 是相同的。 jQuery 稍有不同，因为它针对的是父元素而不是子元素。 （适用于 FF 和 Chrome）

示例 2 - 不起作用！ HTML 和 CSS 是相同的。 jQuery 稍有不同，因为它针对的是子元素而不是父元素。 （适用于 FF 但不适用于 Chrome）

发生了什么？ 在第一种情况下，jQuery 使用 BLUR 动画定位父级，并且正如预期的那样，在滚动时模糊和取消模糊。

怎么了？ 在第二个示例中，除了不是针对父级之外，所有内容都相同，我想仅模糊字母“S”并单独保留“T”。

如您所见，在第一种情况下工作的相同模糊样式类也适用于第二种情况。但是 - 当样式应用于第二种情况时，它们实际上并没有影响元素。没有模糊，没有边界（我添加用于测试）。

有人知道为什么这个动画会在父元素上起作用，影响子元素，但在针对特定子元素时不起作用？

谢谢！

示例 1（有效）

jQuery(document).ready(function($) {

	// Smooth OUT
	$('#smooth-logo').waypoint(function(direction) {
		
		if (direction === 'down') {

			$('#smooth-logo').addClass('swirl-in-fwd');
			$('#smooth-logo').removeClass('swirl-in-bkw');

		} else if (direction === 'up') {  

			$('#smooth-logo').addClass('swirl-in-bkw');
			$('#smooth-logo').removeClass('swirl-in-fwd');
		}
	}, 
		
	{ offset: '0%' });
	
});

.header {
  min-height: 2000px;
  position: relative;
}

#smooth-logo {
  position: fixed;
}

/* SCROLLING ANIMATIONS */
.swirl-in-fwd {
  animation: text-blur-out 1.2s cubic-bezier(0.550, 0.085, 0.680, 0.530) both;
  border: 1px solid red;
}
.swirl-in-bkw {
  animation: text-blur-in 1.2s cubic-bezier(0.550, 0.085, 0.680, 0.530) both;
  border: 1px solid blue;
}


/* SCROLLING ANIMATIONS */

@keyframes text-blur-out {
  0% {
    -webkit-filter: blur(0.01);
            filter: blur(0.01);
  }
  100% {
    -webkit-filter: blur(12px) opacity(0%);
            filter: blur(12px) opacity(0%);
  }
}
@keyframes text-blur-in {
  0% {
    -webkit-filter: blur(12px) opacity(0%);
            filter: blur(12px) opacity(0%);
  }
  100% {

    -webkit-filter: blur(0.01);
            filter: blur(0.01);
  }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/waypoints/4.0.1/jquery.waypoints.min.js"></script>
<script src="../custom.js"></script>
<link href="smooth.css" rel="stylesheet" type="text/css">

<header class="header">
<div id="smooth-logo">
	<svg data-name="big-s" xmlns="http://www.w3.org/2000/svg" width="10in" height="2in" viewBox="0 0 2036.7197 612">
		<title>Stable Smooth Logo</title>

		<!-- BIG S -->
		<path id="bigS" class="" d="M362.2168,367.2317c23.8106,16.6907,51.0516,32.82,83.83,32.82,32.1888,0,56.8072-10.392,56.8072-33.4934,0-22.7209-10.6044-34.0863-70.4407-43.93-59.8364-10.6044-89.757-33.7058-89.757-78.3966,0-46.9588,39.96-79.6635,99.4161-79.6635,36.6579,0,63.8458,7.9425,97.4489,28.7153l-18.0235,37.88c-33.9085-17.7179-47.9607-24.0272-78.4851-24.0272-30.6717,0-49.227,14.75-49.227,35.9591,0,19.3162,10.6044,28.7841,67.4117,38.6325,65.1385,10.98,93.5422,35.2179,93.5422,81.8012,0,49.6124-39.7691,83.9606-109.8293,83.9606-38.3944,0-79.8883-17.5373-102.94-38.04Z"/>

		<!-- BIG T -->
		<polygon id="bigS1" class="" points="682.881 444.996 682.881 215.385 581.132 215.385 602.355 171.38 842.615 171.38 821.253 215.385 731.83 215.385 731.83 444.996 682.881 444.996"/>

	</svg>
</div>
</header>

示例 2（即使样式已应用于元素也不起作用）

jQuery(document).ready(function($) {

	// Smooth OUT
	$('#smooth-logo').waypoint(function(direction) {
		
		if (direction === 'down') {

			$('#bigS').addClass('swirl-in-fwd');
			$('#bigS').removeClass('swirl-in-bkw');

		} else if (direction === 'up') {  

			$('#bigS').addClass('swirl-in-bkw');
			$('#bigS').removeClass('swirl-in-fwd');
		}
	}, 
		
	{ offset: '0%' });
	
});

.header {
  min-height: 2000px;
  position: relative;
}

#smooth-logo {
  position: fixed;
}

/* SCROLLING ANIMATIONS */
.swirl-in-fwd {
  animation: text-blur-out 1.2s cubic-bezier(0.550, 0.085, 0.680, 0.530) both;
  border: 1px solid red;
}
.swirl-in-bkw {
  animation: text-blur-in 1.2s cubic-bezier(0.550, 0.085, 0.680, 0.530) both;
  border: 1px solid blue;
}


/* SCROLLING ANIMATIONS */

@keyframes text-blur-out {
  0% {
    -webkit-filter: blur(0.01);
            filter: blur(0.01);
  }
  100% {
    -webkit-filter: blur(12px) opacity(0%);
            filter: blur(12px) opacity(0%);
  }
}
@keyframes text-blur-in {
  0% {
    -webkit-filter: blur(12px) opacity(0%);
            filter: blur(12px) opacity(0%);
  }
  100% {

    -webkit-filter: blur(0.01);
            filter: blur(0.01);
  }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/waypoints/4.0.1/jquery.waypoints.min.js"></script>
<script src="../custom.js"></script>
<link href="smooth.css" rel="stylesheet" type="text/css">

<header class="header">
<div id="smooth-logo">
	<svg data-name="big-s" xmlns="http://www.w3.org/2000/svg" width="10in" height="2in" viewBox="0 0 2036.7197 612">
		<title>Stable Smooth Logo</title>

		<!-- BIG S -->
		<path id="bigS" class="" d="M362.2168,367.2317c23.8106,16.6907,51.0516,32.82,83.83,32.82,32.1888,0,56.8072-10.392,56.8072-33.4934,0-22.7209-10.6044-34.0863-70.4407-43.93-59.8364-10.6044-89.757-33.7058-89.757-78.3966,0-46.9588,39.96-79.6635,99.4161-79.6635,36.6579,0,63.8458,7.9425,97.4489,28.7153l-18.0235,37.88c-33.9085-17.7179-47.9607-24.0272-78.4851-24.0272-30.6717,0-49.227,14.75-49.227,35.9591,0,19.3162,10.6044,28.7841,67.4117,38.6325,65.1385,10.98,93.5422,35.2179,93.5422,81.8012,0,49.6124-39.7691,83.9606-109.8293,83.9606-38.3944,0-79.8883-17.5373-102.94-38.04Z"/>

		<!-- BIG T -->
		<polygon id="bigS1" class="" points="682.881 444.996 682.881 215.385 581.132 215.385 602.355 171.38 842.615 171.38 821.253 215.385 731.83 215.385 731.83 444.996 682.881 444.996"/>

	</svg>
</div>
</header>

Answer 1

不同之处在于，在第一个示例中，您将 CSS 过滤器功能应用于 HTML 元素。在第二个中，您将 CSS 过滤器功能应用于 SVG 子元素。并非所有浏览器都支持在 SVG 元素上使用过滤器功能。

解决方法是改用 SVG 滤镜和动画。

请注意，SVG 动画在 IE/Edge 中不起作用。因此，您可能需要为此使用 polyfill。见https://leunen.me/fakesmile/

jQuery(document).ready(function($) {

	// Smooth OUT
	$('#smooth-logo').waypoint(function(direction) {
		
		if (direction === 'down') {

			$('#bigS').addClass('swirl-in-fwd');
			$('#bigS').removeClass('swirl-in-bkw');
			$('#animOut').get(0).beginElement(); // restart the animation

		} else if (direction === 'up') {  

			$('#bigS').addClass('swirl-in-bkw');
			$('#bigS').removeClass('swirl-in-fwd');
			$('#animIn').get(0).beginElement(); // restart the animation
		}
	}, 
		
	{ offset: '0%' });
	
});

.header {
  min-height: 2000px;
  position: relative;
}

#smooth-logo {
  position: fixed;
}

/* SCROLLING ANIMATIONS */
.swirl-in-fwd {
  filter: url(#filt-blur-out);
}
.swirl-in-bkw {
  filter: url(#filt-blur-in);
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/waypoints/4.0.1/jquery.waypoints.min.js"></script>
<script src="../custom.js"></script>
<link href="smooth.css" rel="stylesheet" type="text/css">

<header class="header">
<div id="smooth-logo">
	<svg data-name="big-s" xmlns="http://www.w3.org/2000/svg" width="10in" height="2in" viewBox="0 0 2036.7197 612">
		<title>Stable Smooth Logo</title>
    <defs>
      <filter id="filt-blur-out" x="-50%" y="-50%" width="200%" height="200%">
        <feGaussianBlur in="SourceGraphic" stdDeviation="0" result="blurpart">
          <animate id="animOut"
                   attributeName="stdDeviation" from="0" to="50" dur="1.2s" fill="freeze" begin="indefinite"
                   calcMode="spline" keyTimes="0; 1" keySplines="0.550 0.085 0.680 0.530"/>
        </feGaussianBlur>
        <feFlood flood-color="white" flood-opacity="1" result="alphapart">
          <animate attributeName="flood-opacity" from="1" to="0" dur="1.2s" fill="freeze" begin="animOut.begin"
                   calcMode="spline" keyTimes="0; 1" keySplines="0.550 0.085 0.680 0.530"/>
        </feFlood>
        <feComposite in="blurpart" in2="alphapart" operator="in"/>
      </filter>
      
      <filter id="filt-blur-in" x="-50%" y="-50%" width="200%" height="200%">
        <feGaussianBlur in="SourceGraphic" stdDeviation="50" result="blurpart">
          <animate id="animIn"
                   attributeName="stdDeviation" from="50" to="0" dur="1.2s" fill="freeze" begin="indefinite"
                   calcMode="spline" keyTimes="0; 1" keySplines="0.550 0.085 0.680 0.530"/>
        </feGaussianBlur>
        <feFlood flood-color="white" flood-opacity="0" result="alphapart">
          <animate attributeName="flood-opacity" from="0" to="1" dur="1.2s" fill="freeze" begin="animIn.begin"
                   calcMode="spline" keyTimes="0; 1" keySplines="0.550 0.085 0.680 0.530"/>
        </feFlood>
        <feComposite in="blurpart" in2="alphapart" operator="in"/>
      </filter>
    </defs>

		<!-- BIG S -->
		<path id="bigS" class="" d="M362.2168,367.2317c23.8106,16.6907,51.0516,32.82,83.83,32.82,32.1888,0,56.8072-10.392,56.8072-33.4934,0-22.7209-10.6044-34.0863-70.4407-43.93-59.8364-10.6044-89.757-33.7058-89.757-78.3966,0-46.9588,39.96-79.6635,99.4161-79.6635,36.6579,0,63.8458,7.9425,97.4489,28.7153l-18.0235,37.88c-33.9085-17.7179-47.9607-24.0272-78.4851-24.0272-30.6717,0-49.227,14.75-49.227,35.9591,0,19.3162,10.6044,28.7841,67.4117,38.6325,65.1385,10.98,93.5422,35.2179,93.5422,81.8012,0,49.6124-39.7691,83.9606-109.8293,83.9606-38.3944,0-79.8883-17.5373-102.94-38.04Z"/>

		<!-- BIG T -->
		<polygon id="bigS1" class="" points="682.881 444.996 682.881 215.385 581.132 215.385 602.355 171.38 842.615 171.38 821.253 215.385 731.83 215.385 731.83 444.996 682.881 444.996"/>

	</svg>
</div>
</header>