Determine how the scale of a transform changes over time by calculating the function of elapsed time [ transform: scale(x, y

Question

Determine how the scale of a transform changes over time by calculating the function of elapsed time [ transform: scale(x, y

I am currently working on a container that can be expanded and collapsed simply by clicking on a chevron icon. The functionality to collapse or expand the container resides within a function called transformAnimation. This function code closely resembles the example provided in the MDN web docs for requestAnimationFrame. To animate the scaling of the container, I have followed the guidelines outlined in an informative article titled Building performant expand & collapse animations on the Chrome Developers website.

However, I’ve encountered a challenge while trying to calculate the value of yScale, which essentially represents the scaleY() function for the collapse/expand animation based on the elapsed time since the start of the animation.

To further clarify, imagine the container is initially in the expanded state with a yScale value of 6. When the user triggers the toggle button, I expect the yScale value to smoothly decrease from 6 (expanded) to 1 (collapsed) over a specific duration that I control. This behavior mirrors the functionality provided by the CSS property transition-duration: 2s, where the animation duration is adjustable.

Despite my efforts, the current code used to compute the yScale value is not functioning as intended.

// JavaScript code snippets here
// ...

// CSS styles go here
// ...

<!DOCTYPE html>
<html>

<head>
  <link rel="stylesheet" href="css.css">
</head>

<body>
  <div class="drag-expandable-container">
    <!-- HTML content structure goes here -->
  </div>
</body>
<script type="text/javascript" src="js.js"></script>

</html>

javascript html css animation math

Answer 1

Answer №1

Sharing this as a solution for improved code presentation.

It appears that the task you are attempting to accomplish can be done using Linear Interpolation (abbreviated as "lerp" in the developer community).

You can refer to the following simple function:

function lerp(v0, v1, t) {
    return v0*(1-t)+v1*t
}

This is a basic linear interpolation function that should work well for your calculations. It requires three parameters:

v0, the initial value, e.g., 0
v1, the final value, e.g., 10
t, a value between 0 and 1 representing the progression percentage from v0 to v1

For instance, when you call lerp(0, 10, 0.5), it will return 5, indicating halfway between 0 and 10.

If you were to call lerp(0, 10, 0.9), it would yield 9.

In addition, with t = 0, the function outputs 0, and with t = 1, it gives 10.

Applying this concept to your scenario, you have two container heights:

y0 = height when minimized (0)
y1 = height when maximized (6)

Along with elapsed time (et) and total time (tt) of 2 seconds for opening and closing the container.

We aim to use lerp to obtain the yScale at a specific time t.

While we already know y0 and y1, et cannot directly serve as the t parameter since et ranges from 0 to 2 while t must range from 0 to 1.

To address this, we need to scale et to fit within 0 and 1.

Here's a complete code snippet demonstrating scaling and utilizing lerp:

// Y scale value when minimized
let y0 = 0;
// Y scale value when maximized
let y1 = 6;
// Time taken to transition from 0 to 6
let totalTime = 2000;

// The lerp function
function lerp(v0, v1, t) {
    return v0*(1-t)+v1*t
}

// Simulating the lerp function over time from 0ms to 2000ms
for(let elapsed_time = 0; elapsed_time <= totalTime; elapsed_time += 100)
{
    // Scaling elapsed time to span from 0 to 1 instead of 0 to 2
    let elapsed_time_scaled = elapsed_time / totalTime;
    // Calculating y scale with lerp at the current time
    let scale_y = lerp(y0, y1, elapsed_time_scaled).toFixed(2);

    // Displaying the results
    console.log(elapsed_time, elapsed_time_scaled, scale_y);
}

The output resembles:

0 0 '0.00'
100 0.05 '0.30'
200 0.1 '0.60'
300 0.15 '0.90'
400 0.2 '1.20'
500 0.25 '1.50'
600 0.3 '1.80'
700 0.35 '2.10'
800 0.4 '2.40'
900 0.45 '2.70'
1000 0.5 '3.00'
1100 0.55 '3.30'
1200 0.6 '3.60'
1300 0.65 '3.90'
1400 0.7 '4.20'
1500 0.75 '4.50'
1600 0.8 '4.80'
1700 0.85 '5.10'
1800 0.9 '5.40'
1900 0.95 '5.70'
2000 1 '6.00'

Looks promising! Do you find this helpful?

Answer 2

Sharing this as a solution for improved code presentation.

It appears that the task you are attempting to accomplish can be done using Linear Interpolation (abbreviated as "lerp" in the developer community).

You can refer to the following simple function:

function lerp(v0, v1, t) {
    return v0*(1-t)+v1*t
}

This is a basic linear interpolation function that should work well for your calculations. It requires three parameters:

v0, the initial value, e.g., 0
v1, the final value, e.g., 10
t, a value between 0 and 1 representing the progression percentage from v0 to v1

For instance, when you call lerp(0, 10, 0.5), it will return 5, indicating halfway between 0 and 10.

If you were to call lerp(0, 10, 0.9), it would yield 9.

In addition, with t = 0, the function outputs 0, and with t = 1, it gives 10.

Applying this concept to your scenario, you have two container heights:

y0 = height when minimized (0)
y1 = height when maximized (6)

Along with elapsed time (et) and total time (tt) of 2 seconds for opening and closing the container.

We aim to use lerp to obtain the yScale at a specific time t.

While we already know y0 and y1, et cannot directly serve as the t parameter since et ranges from 0 to 2 while t must range from 0 to 1.

To address this, we need to scale et to fit within 0 and 1.

Here's a complete code snippet demonstrating scaling and utilizing lerp:

// Y scale value when minimized
let y0 = 0;
// Y scale value when maximized
let y1 = 6;
// Time taken to transition from 0 to 6
let totalTime = 2000;

// The lerp function
function lerp(v0, v1, t) {
    return v0*(1-t)+v1*t
}

// Simulating the lerp function over time from 0ms to 2000ms
for(let elapsed_time = 0; elapsed_time <= totalTime; elapsed_time += 100)
{
    // Scaling elapsed time to span from 0 to 1 instead of 0 to 2
    let elapsed_time_scaled = elapsed_time / totalTime;
    // Calculating y scale with lerp at the current time
    let scale_y = lerp(y0, y1, elapsed_time_scaled).toFixed(2);

    // Displaying the results
    console.log(elapsed_time, elapsed_time_scaled, scale_y);
}

The output resembles:

0 0 '0.00'
100 0.05 '0.30'
200 0.1 '0.60'
300 0.15 '0.90'
400 0.2 '1.20'
500 0.25 '1.50'
600 0.3 '1.80'
700 0.35 '2.10'
800 0.4 '2.40'
900 0.45 '2.70'
1000 0.5 '3.00'
1100 0.55 '3.30'
1200 0.6 '3.60'
1300 0.65 '3.90'
1400 0.7 '4.20'
1500 0.75 '4.50'
1600 0.8 '4.80'
1700 0.85 '5.10'
1800 0.9 '5.40'
1900 0.95 '5.70'
2000 1 '6.00'

Looks promising! Do you find this helpful?

Determine how the scale of a transform changes over time by calculating the function of elapsed time [ transform: scale(x, y

Answer №1

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