Optimizing Lottie Animations with CSS: Overcoming Preloading Challenges

When enhancing user experience with engaging animations, preload strategies become crucial—especially for complex animations like Lottie files involving multiple image frames. In my recent project, I aimed to replicate a 3D rotation effect on energy cans using CSS instead of Lottie, hoping to improve loading performance. However, I encountered difficulties ensuring that all image frames are preloaded properly.

Background on the Project:
I am reconstructing a web design practice site originally built in Webflow, now rebuilt using HTML, CSS, and JavaScript to gain more control over interactions. One feature I implemented is a hover-triggered 3D rotation of energy cans, previously achieved with a Lottie animation. The challenge was that on the initial hover, all frames of the animation would load instantaneously, causing unwanted blinking and layout shifts. Efforts to preload the frames via JavaScript—such as playing the animation once beforehand—did not yield the desired results.

The Problem:
The core issue lies in ensuring all image frames for the animation are preloaded before user interaction. Without this, the first hover triggers loading delays that disrupt the smoothness of the animation, leading to a poorer user experience.

Proposed Solution:
While replacing a Lottie with CSS is a feasible approach, preloading image sequences remains a challenge. To address this, consider the following strategies:

1. Preload Images with JavaScript:
   Use JavaScript to load all image frames during page load. For example, create an array of Image objects with the src set to each frame, and wait for all to load before enabling hover interactions.

2. CSS Sprite Sheets:
   Instead of individual images, combine all frames into a single sprite sheet and animate the background position. This reduces HTTP requests and can improve preload efficiency.

3. Optimize Asset Delivery:
   Compress images, serve them via a CDN, and utilize browser caching headers to minimize load times.

4. Implement Lazy Loading with Caching:
   Use the loading="lazy" attribute where applicable, and ensure the images are loaded into cache early in the page lifecycle.

Further Resources:
For a detailed breakdown of preloading techniques and creating seamless CSS-based animations, refer to online tutorials on sprite animations, JavaScript preloading, and best practices for optimizing animations.

Project Link:
You can view the current implementation and experiment with the project here: [https://mitchangus.design/LiftOff