How do I repeatedly interpolate linearly between two values within a requestAnimationFrame loop

To repeatedly interpolate linearly between two values within a requestAnimationFrame loop, you can calculate the intermediate values at each frame using the elapsed time and the duration of the animation. Here's a step-by-step guide on how to achieve this:

1. Define the Animation Parameters: Start by defining the animation parameters, such as the start value, end value, and duration of the interpolation.

2. Calculate the Step: In the requestAnimationFrame loop, calculate the current elapsed time since the animation started.

3. Calculate the Interpolated Value: Use the elapsed time and the duration to calculate the interpolation factor. Then, use the interpolation factor to compute the intermediate value between the start and end values.

4. Update the Animation State: Update your application state or UI with the interpolated value.

5. End the Animation: End the animation when the elapsed time reaches the duration, and update your application state with the final value.

Here's an example implementation using JavaScript:

javascriptCopy code
const startValue = 0;
const endValue = 100;
const duration = 1000; // Animation duration in milliseconds

let startTime = null;

function interpolateValue(timestamp) {
  if (!startTime) startTime = timestamp;
  const elapsedTime = timestamp - startTime;

  if (elapsedTime >= duration) {
    // Animation finished
    const finalValue = endValue;
    console.log('Animation finished. Final value:', finalValue);
    // Update your application state or UI with the finalValue here
  } else {
    // Calculate the interpolation factor (a value between 0 and 1)
    const interpolationFactor = elapsedTime / duration;

    // Calculate the interpolated value between startValue and endValue
    const interpolatedValue = startValue + interpolationFactor * (endValue - startValue);
    console.log('Interpolated value:', interpolatedValue);

    // Update your application state or UI with the interpolatedValue here

    // Continue the animation
    requestAnimationFrame(interpolateValue);
  }
}

// Start the animation by calling requestAnimationFrame
requestAnimationFrame(interpolateValue);

In this example, the interpolateValue function is called recursively inside the requestAnimationFrame loop. The interpolateValue function calculates the elapsed time, checks if the animation has finished, calculates the interpolation factor, and computes the intermediate value to update the application state or UI.

The animation will smoothly transition between startValue and endValue over the specified duration (1 second in this example). You can adjust the startValue, endValue, and duration to suit your specific use case.

By using this approach, you can create smooth animations that repeatedly interpolate linearly between two values within the requestAnimationFrame loop.