SVG animation with SMIL
Synchronized Multimedia Integration Language (SMIL) is an XML-based language for writing interactive multimedia presentations. Authors can use SMIL syntax in other XML-based languages to define the timing and layout of elements for animation.
SMIL allows you to:
- animate the numeric attributes of an element (x, y, etc.)
- animate transform attributes (translation, rotate, etc.)
- animate color attributes
- follow a motion path
The following sections show how to use SMIL in SVG for these four use cases.
Animating attributes of an element
The following example animates the cx attribute of a circle. To do so, we add an <animate> element inside the <circle> element. The important attributes for <animate> are:
attributeName-
The name of the attribute to animate.
from-
The initial value of the attribute.
to-
The final value.
dur-
The duration of the animation (for example, write '5s' for 5 seconds).
If you want to animate more attributes inside the same element, you can add more <animate> elements.
<svg width="300" height="100">
<title>Attribute Animation with SMIL</title>
<rect x="0" y="0" width="300" height="100" stroke="black" stroke-width="1" />
<circle cx="0" cy="50" r="15" fill="blue" stroke="black" stroke-width="1">
<animate
attributeName="cx"
from="0"
to="500"
dur="5s"
repeatCount="indefinite" />
</circle>
</svg>
Animating the transform attributes
The <animateTransform> element let you animate transform attributes. This element is necessary because we are not animating a single attribute like x which is a number. Rotation attributes look like this: rotation(theta, x, y), where theta is the angle in degrees, and x and y are absolute positions. In the example below, we animate the center of the rotation and the angle.
<svg width="300" height="100">
<title>SVG SMIL Animate with transform</title>
<rect x="0" y="0" width="300" height="100" stroke="black" stroke-width="1" />
<rect
x="0"
y="50"
width="15"
height="34"
fill="blue"
stroke="black"
stroke-width="1">
<animateTransform
attributeName="transform"
begin="0s"
dur="20s"
type="rotate"
from="0 60 60"
to="360 100 60"
repeatCount="indefinite" />
</rect>
</svg>
Animation following a path
The <animateMotion> element lets you animate an element position and rotation according to a path. The path is defined the same way as in <path>. You can set the attribute to define whether the object rotates following the tangent of the path.
Example 1: Linear motion
In this example, a blue circle bounces between the left and right edges of a black box, over and over again, indefinitely. The animation here is handled by the <animateMotion> element. In this case, we're establishing a path consisting of a MoveTo command to define the starting point for the animation, then the Horizontal-line command to move the circle 300 pixels to the right, followed by the Z command, which closes the path, establishing a loop back to the beginning. By setting the value of the repeatCount attribute to indefinite, we indicate that the animation should loop forever, as long as the SVG image exists.
<svg xmlns="http://www.w3.org/2000/svg" width="300" height="100">
<title>SVG SMIL Animate with Path</title>
<rect x="0" y="0" width="300" height="100" stroke="black" stroke-width="1" />
<circle cx="0" cy="50" r="15" fill="blue" stroke="black" stroke-width="1">
<animateMotion path="M 0 0 H 300 Z" dur="3s" repeatCount="indefinite" />
</circle>
</svg>
Example 2: Curved motion
Same example as before with a curved path and following the direction of the path.
<svg width="300" height="100">
<title>SVG SMIL Animate with Path</title>
<rect x="0" y="0" width="300" height="100" stroke="black" stroke-width="1" />
<rect
x="0"
y="0"
width="20"
height="20"
fill="blue"
stroke="black"
stroke-width="1">
<animateMotion
path="M 250,80 H 50 Q 30,80 30,50 Q 30,20 50,20 H 250 Q 280,20,280,50 Q 280,80,250,80Z"
dur="3s"
repeatCount="indefinite"
rotate="auto" />
</rect>
</svg>