How to use CSS and D3 to implement interactive animation of small fish swimming (with code)

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Effect preview

Source code download

https://github.com/comehope/front- end-daily-challenges

Code Interpretation

Define dom, the sub-elements contained in the container represent the body, eyes, dorsal fin and tail of the fish respectively:

<div>
    <span></span>
    <span></span>
    <span></span>
    <span></span>
</div>

Set page style For full screen and no scroll bars:

body {
    margin: 0;
    width: 100vw;
    height: 100vh;
    background-color: #222;
    overflow: hidden;
}

Define the container size of the fish, --r is a basic size unit, and all subsequent sizes are calculated based on it:

.fish {
    position: absolute;
    --r: 15vw;
    width: calc(var(--r) + var(--r) / 3);
    height: calc(var(--r) * 2);
    left: 50%;
    top: 100px;
}

Draw the body of the fish, and declare the color of the fish to the parent class, because this color will be used below:

.fish {
    color: hsl(0, 50%, 50%);
}

.fish .body {
    position: absolute;
    border: var(--r) solid transparent;
    border-right-color: currentColor;
    border-left-style: none;
}

Draw the eyes of the fish:

.fish .eye {
    position: absolute;
    --r1: calc(var(--r) / 4);
    width: var(--r1);
    height: var(--r1);
    background-color: #111;
    border-radius: 50%;
    top: 35%;
    left: 30%;
}

Draw The dorsal fin of the fish:

.fish .fin {
    position: absolute;
    --r2: calc(var(--r) / 2);
    border-bottom: var(--r2) solid;
    border-left: var(--r2) solid transparent;
    filter: brightness(2.5);
    left: calc(var(--r) - var(--r2));
}

Draw the tail of the fish:

.fish .tail {
    position: absolute;
    --r3: calc(var(--r) / 3);
    border: var(--r3) solid transparent;
    border-right-color: currentColor;
    border-left-style: none;
    right: 0;
    top: calc(var(--r) - var(--r3));
}

Add the animation effect for the fish to swim, not to execute it in a loop, but only once:

.fish {
    right: calc(var(--r) * -1);
    animation: run 3s linear forwards;
}

@keyframes run {
    to {
        right: 100%;
    }
}

Then add the animation effect of the swaying of the fish when swimming:

.fish {
    animation: 
        run 3s linear forwards,
        shake 0.3s linear infinite;
}

@keyframes shake {
    50% {
        transform: rotateY(-30deg);
    }

    100% {
        transform: rotateY(30deg);
    }
}

Next, set some variables to create different-looking fish:

Variables for the size of the fish--size, the larger the value, the larger the size:

.fish {
    --size: 5;
    --r: calc(var(--size) * 1vw);
}

The color variable of the fish--color, indicating the angle of the hue circle:

.fish {
    --color: 0;
    color: hsl(var(--color), 50%, 50%);
}

The fish swims from the right to the left The duration on the side, the shorter the duration, the faster the fish swims:

.fish {
    --duration: 3;
    animation: 
        run calc(var(--duration) * 1s) linear forwards,
        shake 0.3s linear infinite;
}

The height at which the fish appears, the larger the data, the closer it is to the lower part of the page:

.fish {
    --top: 100;
    top: calc(var(--top) * 1px);
}

Next, use d3 to batch process dom elements and css variables .
Introduce the d3 library:

<script></script>

Delete the .fish element in the html and the variable declaration code in the css file. Create a function that generates a fish. The values ​​of css variables are randomly generated. The value range of --size is 5 ~ 8, the value range of --color is -60 ~ 15, - The value range of -duration is 3 ~ 6, the value range of --top is 100 ~ 300:

function buildFish() {
    let fish = d3.select('body')
        .append('p')
        .attr('class', 'fish')
        .style('--size', d3.randomUniform(5, 8)())
        .style('--color', d3.randomUniform(-60, 15)())
        .style('--duration', d3.randomUniform(3, 6)())
        .style('--top', d3.randomUniform(100, 300)());
    
    fish.append('span').attr('class', 'body');
    fish.append('span').attr('class', 'eye');
    fish.append('span').attr('class', 'fin');
    fish.append('span').attr('class', 'tail');
}

binds the mouse click event. When the mouse is pressed A fish is generated when the It goes blank after loading:

function buildFish(e) {
    //略....
    .style('--top', e.clientY);
}

window.addEventListener('click', buildFish);

Done!

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