Animate a point along a route
You can utilize the Turf library to create seamless animations of a point moving along the length of a line.
NPM module setup
npm install --save @maptiler/sdk @turf/turf
import { Map, MapStyle, config } from '@maptiler/sdk';
import '@maptiler/sdk/dist/maptiler-sdk.css';
import * as turf from '@turf/turf';
config.apiKey = 'YOUR_MAPTILER_API_KEY_HERE';
const map = new Map({
container: 'map',
style: MapStyle.STREETS,
center: [-96, 37.8],
zoom: 3
});
// San Francisco
const origin = [-122.414, 37.776];
// Washington DC
const destination = [-77.032, 38.913];
// A simple line from origin to destination.
const route = {
'type': 'FeatureCollection',
'features': [
{
'type': 'Feature',
'geometry': {
'type': 'LineString',
'coordinates': [origin, destination]
}
}
]
};
// A single point that animates along the route.
// Coordinates are initially set to origin.
const point = {
'type': 'FeatureCollection',
'features': [
{
'type': 'Feature',
'properties': {},
'geometry': {
'type': 'Point',
'coordinates': origin
}
}
]
};
// Calculate the distance in kilometers between route start/end point.
const lineDistance = turf.length(route.features[0], 'kilometers');
const arc = [];
// Number of steps to use in the arc and animation, more steps means
// a smoother arc and animation, but too many steps will result in a
// low frame rate
const steps = 500;
// Draw an arc between the `origin` & `destination` of the two points
for (let i = 0; i < lineDistance; i += lineDistance / steps) {
const segment = turf.along(route.features[0], i, 'kilometers');
arc.push(segment.geometry.coordinates);
}
// Update the route with calculated arc coordinates
route.features[0].geometry.coordinates = arc;
// Used to increment the value of the point measurement against the route.
let counter = 0;
map.on('load', function () {
// Add a source and layer displaying a point which will be animated in a circle.
map.addSource('route', {
'type': 'geojson',
'data': route
});
map.addSource('point', {
'type': 'geojson',
'data': point
});
map.addLayer({
'id': 'route',
'source': 'route',
'type': 'line',
'paint': {
'line-width': 2,
'line-color': '#007cbf'
}
});
map.addLayer({
'id': 'point',
'source': 'point',
'type': 'symbol',
'layout': {
'icon-image': 'airport',
'icon-rotate': ['get', 'bearing'],
'icon-rotation-alignment': 'map',
'icon-overlap': 'always',
'icon-ignore-placement': true
}
});
function animate() {
// Update point geometry to a new position based on counter denoting
// the index to access the arc.
point.features[0].geometry.coordinates =
route.features[0].geometry.coordinates[counter];
// Calculate the bearing to ensure the icon is rotated to match the route arc
// The bearing is calculate between the current point and the next point, except
// at the end of the arc use the previous point and the current point
point.features[0].properties.bearing = turf.bearing(
turf.point(
route.features[0].geometry.coordinates[
counter >= steps ? counter - 1 : counter
]
),
turf.point(
route.features[0].geometry.coordinates[
counter >= steps ? counter : counter + 1
]
)
);
// Update the source with this new data.
map.getSource('point').setData(point);
// Request the next frame of animation so long the end has not been reached.
if (counter < steps) {
requestAnimationFrame(animate);
}
counter = counter + 1;
}
document
.getElementById('replay')
.addEventListener('click', function () {
// Set the coordinates of the original point back to origin
point.features[0].geometry.coordinates = origin;
// Update the source layer
map.getSource('point').setData(point);
// Reset the counter
counter = 0;
// Restart the animation.
animate(counter);
});
// Start the animation.
animate(counter);
});
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="robots" content="noindex">
<title>Animate a point along a route | NPM example</title>
<link rel="stylesheet" href="./style.css">
</head>
<body>
<div id="map"></div>
<div class="overlay">
<button id="replay">Replay</button>
</div>
<script type="module" src="./main.js"></script>
</body>
</html>
body {margin: 0; padding: 0;}
#map {position: absolute; top: 0; bottom: 0; width: 100%;}
.overlay {
position: absolute;
top: 10px;
left: 10px;
}
.overlay button {
font: 600 12px/20px 'Helvetica Neue', Arial, Helvetica, sans-serif;
background-color: #3386c0;
color: #fff;
display: inline-block;
margin: 0;
padding: 10px 20px;
border: none;
cursor: pointer;
border-radius: 3px;
}
.overlay button:hover {
background-color: #4ea0da;
}
