How to create animations on a canvas using requestAnimationFrame()?
Jun 22, 2025 am 12:52 AM
The key to using requestAnimationFrame() to implement smooth animation on HTML Canvas is to understand its operating mechanism and cooperate with the Canvas drawing process. 1. requestAnimationFrame() is an API designed for animation by the browser. It can be synchronized with the screen refresh rate to avoid lag or tear, and is more efficient than setTimeout or setInterval; 2. The animation infrastructure includes preparing canvas elements, obtaining context, and defining the main loop function animate(), where the canvas is cleared and the next frame is requested for continuous redrawing; 3. To achieve dynamic effects, state variables, such as the coordinates of the ball, are updated in each frame, thereby forming continuous animation; 4. To improve expression, it can be achieved by adding time control to ensure speed consistency, using double buffering technology to optimize rendering, and using easing functions to enhance the naturalness of motion. After mastering these core points, you can create a variety of animation effects through creative and detailed adjustments.
Want to use requestAnimationFrame() to make smooth animations on HTML Canvas? This is actually not difficult. The key is to understand its operating mechanism and cooperate with Canvas' drawing process.
Basic principle: Why choose requestAnimationFrame()
requestAnimationFrame() is an API designed specifically for animation by the browser. It calls the specified function before the next repaint, which ensures that the animation is synchronized with the screen refresh rate (usually 60Hz, which is 60 frames per second), thereby avoiding lag or tearing.
It is more efficient than setTimeout or setInterval because the browser can automatically optimize multiple animations, reduce resource usage, and even pause execution when the page is invisible.
Building infrastructure: Canvas and main loop
First prepare your HTML page and insert a <canvas></canvas> element:
<canvas id="myCanvas" width="800" height="600"></canvas>
Then get the context in JS and start the animation loop:
const canvas = document.getElementById('myCanvas');
const ctx = canvas.getContext('2d');
function animate() {
// Clear canvas ctx.clearRect(0, 0, canvas.width, canvas.height);
// Draw content drawSomething();
// Request the next frame requestAnimationFrame(animate);
}
animate(); // Start the first frameThe key point is to clear the canvas before each drawing, otherwise the content of the previous frame will remain. This structure is the basis of all your animation logic.
Implement dynamic effects: add state changes
To make the picture move, certain variables need to be constantly changed. For example, drawing a moving ball:
let x = 0;
function drawSomething() {
ctx.beginPath();
ctx.arc(x, 100, 10, 0, Math.PI * 2);
ctx.fillStyle = 'red';
ctx.fill();
ctx.closePath();
x = 2;
if (x > canvas.width) {
x = 0;
}
} In this example, x represents the horizontal coordinate of the ball. Update this value every frame, and then re-draw it, you can see the ball move from left to right.
If you want the animation speed to be unaffected by the frame rate, it is recommended to add time control, such as recording the start time and calculating the elapsed time difference to determine the position.
Improve expressiveness: add details to make it more natural
- Double buffering technology is not necessary, but you can consider rendering complex graphics off-screen and drawing them on the main canvas one after another.
- If you have multiple animation objects, you can save their state with an array, and update and draw them uniformly in each frame.
- Remember not to forget to stop looping at the end of the animation, although most of the time you loop infinitely.
- Using the easing function can make the movement more natural, such as slowing in and out.
For example, add a relief effect to the above ball:
let x = 0;
let velocity = 0;
function drawSomething() {
velocity = (targetX - x) * 0.1; // Simple elastic formula x = velocity;
ctx.beginPath();
ctx.arc(x, 100, 10, 0, Math.PI * 2);
ctx.fillStyle = 'red';
ctx.fill();
ctx.closePath();
}Basically that's it. As long as you master the basic structure and changes, all you have to do is to adjust the creativity and details.
The above is the detailed content of How to create animations on a canvas using requestAnimationFrame()?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Using ARIA attributes with HTML5 semantic elements for accessibility
Jul 07, 2025 am 02:54 AM
The reason why ARIA and HTML5 semantic tags are needed is that although HTML5 semantic elements have accessibility meanings, ARIA can supplement semantics and enhance auxiliary technology recognition capabilities. For example, when legacy browsers lack support, components without native tags (such as modal boxes), and state updates need to be dynamically updated, ARIA provides finer granular control. HTML5 elements such as nav, main, aside correspond to ARIArole by default, and do not need to be added manually unless the default behavior needs to be overridden. The situations where ARIA should be added include: 1. Supplement the missing status information, such as using aria-expanded to represent the button expansion/collapse status; 2. Add semantic roles to non-semantic tags, such as using div role to implement tabs and match them
Integrating CSS and JavaScript effectively with HTML5 structure.
Jul 12, 2025 am 03:01 AM
HTML5, CSS and JavaScript should be efficiently combined with semantic tags, reasonable loading order and decoupling design. 1. Use HTML5 semantic tags, such as improving structural clarity and maintainability, which is conducive to SEO and barrier-free access; 2. CSS should be placed in, use external files and split by module to avoid inline styles and delayed loading problems; 3. JavaScript is recommended to be introduced in front, and use defer or async to load asynchronously to avoid blocking rendering; 4. Reduce strong dependence between the three, drive behavior through data-* attributes and class name control status, and improve collaboration efficiency through unified naming specifications. These methods can effectively optimize page performance and collaborate with teams.
HTML5 video not playing in Chrome
Jul 10, 2025 am 11:20 AM
Common reasons why HTML5 videos don't play in Chrome include format compatibility, autoplay policy, path or MIME type errors, and browser extension interference. 1. Videos should be given priority to using MP4 (H.264) format, or provide multiple tags to adapt to different browsers; 2. Automatic playback requires adding muted attributes or triggering .play() with JavaScript after user interaction; 3. Check whether the file path is correct and ensure that the server is configured with the correct MIME type. Local testing is recommended to use a development server; 4. Ad blocking plug-in or privacy mode may prevent loading, so you can try to disable the plug-in, replace the traceless window or update the browser version to solve the problem.
Embedding video content using the HTML5 `` tag.
Jul 07, 2025 am 02:47 AM
Embed web videos using HTML5 tags, supports multi-format compatibility, custom controls and responsive design. 1. Basic usage: add tags and set src and controls attributes to realize playback functions; 2. Support multi-formats: introduce different formats such as MP4, WebM, Ogg, etc. through tags to improve browser compatibility; 3. Custom appearance and behavior: hide default controls and implement style adjustment and interactive logic through CSS and JavaScript; 4. Pay attention to details: Set muted and autoplay to achieve automatic playback, use preload to control loading strategies, combine width and max-width to achieve responsive layout, and use add subtitles to enhance accessibility.
Using HTML5 Semantic Elements for Page Structure
Jul 07, 2025 am 02:53 AM
Using HTML5 semantic tags can improve web structure clarity, accessibility and SEO effects. 1. Semantic tags such as,,,, and make it easier for the machine to understand the page content; 2. Each tag has a clear purpose: used in the top area, wrap navigation links, include core content, display independent articles, group relevant content, place sidebars, and display bottom information; 3. Avoid abuse when using it, ensure that only one per page, avoid excessive nesting, reasonable use and in blocks. Mastering these key points can make the web page structure more standardized and practical.
Explaining the HTML5 `` vs `` elements.
Jul 12, 2025 am 03:09 AM
It is a block-level element, suitable for layout; it is an inline element, suitable for wrapping text content. 1. Exclusively occupy a line, width, height and margins can be set, which are often used in structural layout; 2. No line breaks, the size is determined by the content, and is suitable for local text styles or dynamic operations; 3. When choosing, it should be judged based on whether the content needs independent space; 4. It cannot be nested and is not suitable for layout; 5. Priority is given to the use of semantic labels to improve structural clarity and accessibility.
Accessing User Location with HTML5 Geolocation API
Jul 07, 2025 am 02:49 AM
To obtain user location information, you must first obtain authorization. When using HTML5's GeolocationAPI, the first step is to request user permission. If the user refuses or fails to respond, an error should be handled and a prompt should be given; after successful authorization, the Position object includes coords (latitude, longitude, etc.) and timestamp; you can use watchPosition to monitor location changes, but you need to pay attention to performance issues and clear the listener in time. 1. Authorization requires the user to explicitly allow it to trigger the getCurrentPosition method request; 2. Process error.code when rejected or errored and prompt the user; 3. After success, position.coords provides location data; 4.watc
Saving the content of an HTML5 canvas as an image.
Jul 08, 2025 am 02:13 AM
Yes, you can save its contents as an image using the HTML5Canvas built-in toDataURL() method. First, call canvas.toDataURL ('image/png') to convert the canvas content to a base64 string in PNG format; if JPEG or WebP format is required, the corresponding type and quality parameters such as canvas.toDataURL ('image/jpeg', 0.8) can be passed in. Then you can achieve download by creating a dynamic link and triggering a click event: 1. Create an element a; 2. Set the download attribute and href as image data; 3. Call the click() method. Note that this operation should be triggered by user interaction.
