How to use JavaScript to create a spinning wheel that stops automatically at the center of a randomly selected slice

Question

How to use JavaScript to create a spinning wheel that stops automatically at the center of a randomly selected slice

Building on the concept of creating a spinning image with CSS and jQuery, I am looking to take it a step further. In my project, a seven-part wheel spins and the correct values are displayed when it stops spinning. However, I have a specific requirement - I want the wheel to always stop at the center of each section. Currently, the wheel stops randomly, sometimes not on any content. To achieve this, I believe some calculations are needed to determine the center point of each section. How can I incorporate this math into the script to ensure the wheel stops at the center every time?

This is what I have managed to create so far...

<html>
<style>
  .roulette_center {
      position: absolute;
      top: 255px;
      left: 258px;
      cursor: pointer;
    
  }
  .roulette_center:hover {
    transform: scale(1.01);
    
  }

  .roulette_wheel{
    touch-action:auto;pointer-events:painted
  }
</style>
<body>
<div style="z-index: 0; position: relative">
  <span  style="position: absolute; top: 0px; left: 360px; font-weight:700;font-size:24px;" id="score">&nbsp;</span>
  <img class="roulette_wheel" src="https://www.dropbox.com/s/6kp3fmtp72aj3vy/wellness-wheel.png?raw=1" />
  <img class="roulette_center" src="https://www.dropbox.com/s/52x8iyb1nvkjm0w/wheelCenter.png?raw=1" onclick="roulette_spin(this)" onfocus="transform()">
  <div style="position: absolute; top: 30px; left: 350px; background-color: red; width: 1px; height: 60px;"></div>

</div>

<script>
  var force = 0;
  var angle = 0;
  var rota = 1;
  var inertia = 0.985;
  var minForce = 15;
  var randForce = 15;
  var rouletteElem = document.getElementsByClassName('roulette_wheel')[0];
  var scoreElem = document.getElementById('score');

  var values = [
    "Spititual", "Emotional", "Intellectual", "Physical", "Social", "Environmental", "Financial"
  ].reverse();

  function roulette_spin(btn) {
    // set initial force randomly
    force = Math.floor(Math.random() * randForce) + minForce;
    requestAnimationFrame(doAnimation);
  }

  function doAnimation() {
    // new angle is previous angle + force modulo 360 (so that it stays between 0 and 360)
    angle = (angle + force) % 360;
    // decay force according to inertia parameter
    force *= inertia;
    rouletteElem.style.transform = 'rotate(' + angle + 'deg)';
    // stop animation if force is too low
    if (force < 0.05) {
      // score roughly estimated
      scoreElem.innerHTML = values[Math.floor(((angle / 360) * values.length) - 0.5)];
      return;
    }
    requestAnimationFrame(doAnimation);
  }
</script>
</body>
</html>

jquery css

Answer 1

Answer №1

Here you will find a unique solution for achieving elastic-like snapping to the center of the stopping slice.

This approach utilizes an attractor concept to adjust the rotation speed based on a target (the center of the closest slice). This methodology involves vanilla JavaScript and does not rely on CSS transitions.

The strength of the force pulling towards the attractor increases as you get closer to it. The force is calculated as the inverse of the distance to the attractor, with safeguards in place to prevent extreme values when the distance is close to zero (or exactly zero).

This solution is appealing because it simulates the necessary behavior through simple artificial physics (representing wheel inertia and a magnetic effect beneath the wheel slices), allowing the physics to naturally settle after an initial random push.

You have the flexibility to experiment with the physical parameters and stopping conditions, but caution is advised as numerical instabilities can arise easily.

UPDATE:

Controls have been added to the code snippet to facilitate experimentation and comprehension of the physical settings (slider boundaries set to "reasonable" limits)
A bug has been fixed where clicking multiple times on the center button spawned multiple animation handlers concurrently (notably when repeatedly clicking without waiting for the wheel to stop)
The entire functionality now resides within a self-called function to prevent polluting the global scope with variables (the HTML attribute onclick="roulette_spin(this)" has been removed, and
```
document.getElementsByClassName('roulette_center')[0].addEventListener('click', roulette_spin);
```
has been added to bind the localized handler (roulette_spin) to the wheel center)

UPDATE 2:

Detection capability for clicked slice has been implemented
If the wheel spins without a specific slice being clicked, it will halt according to the initial velocity and inertia, snapping to the center of a random slice
When a slice is chosen while the wheel is spinning, the speed will be adjusted so that the wheel halts very close to the targeted slice; ensuring that forcing the attractor to the clicked slice results in a stop on that particular slice. For mathematicians out there: the current formula might lack precision, and any enhancements are welcome to calculate an accurate speed correction for stopping. Despite its imperfections, it delivers satisfactory results...
In instances where the wheel is stationary, selecting a slice will animate the wheel towards the chosen slice. This feature is notable for high friction (low inertia) scenarios, where the wheel swiftly adjusts position and decelerates smoothly. It emulates a rotating menu - potentially aligning with the original poster's objectives.

(For better visibility, view the snippet in full-page mode. Note: the current state does not support multiple clicks on a slice during a spin, leading to a failure. Once a slice is clicked, wait for the wheel to come to a complete stop. Although rectifying this issue was rewarding, I've invested substantial time into this response due to the lockdown restrictions :D)

Answer 2

Here you will find a unique solution for achieving elastic-like snapping to the center of the stopping slice.

This approach utilizes an attractor concept to adjust the rotation speed based on a target (the center of the closest slice). This methodology involves vanilla JavaScript and does not rely on CSS transitions.

The strength of the force pulling towards the attractor increases as you get closer to it. The force is calculated as the inverse of the distance to the attractor, with safeguards in place to prevent extreme values when the distance is close to zero (or exactly zero).

This solution is appealing because it simulates the necessary behavior through simple artificial physics (representing wheel inertia and a magnetic effect beneath the wheel slices), allowing the physics to naturally settle after an initial random push.

You have the flexibility to experiment with the physical parameters and stopping conditions, but caution is advised as numerical instabilities can arise easily.

UPDATE:

Controls have been added to the code snippet to facilitate experimentation and comprehension of the physical settings (slider boundaries set to "reasonable" limits)
A bug has been fixed where clicking multiple times on the center button spawned multiple animation handlers concurrently (notably when repeatedly clicking without waiting for the wheel to stop)
The entire functionality now resides within a self-called function to prevent polluting the global scope with variables (the HTML attribute onclick="roulette_spin(this)" has been removed, and
```
document.getElementsByClassName('roulette_center')[0].addEventListener('click', roulette_spin);
```
has been added to bind the localized handler (roulette_spin) to the wheel center)

UPDATE 2:

Detection capability for clicked slice has been implemented
If the wheel spins without a specific slice being clicked, it will halt according to the initial velocity and inertia, snapping to the center of a random slice
When a slice is chosen while the wheel is spinning, the speed will be adjusted so that the wheel halts very close to the targeted slice; ensuring that forcing the attractor to the clicked slice results in a stop on that particular slice. For mathematicians out there: the current formula might lack precision, and any enhancements are welcome to calculate an accurate speed correction for stopping. Despite its imperfections, it delivers satisfactory results...
In instances where the wheel is stationary, selecting a slice will animate the wheel towards the chosen slice. This feature is notable for high friction (low inertia) scenarios, where the wheel swiftly adjusts position and decelerates smoothly. It emulates a rotating menu - potentially aligning with the original poster's objectives.

(For better visibility, view the snippet in full-page mode. Note: the current state does not support multiple clicks on a slice during a spin, leading to a failure. Once a slice is clicked, wait for the wheel to come to a complete stop. Although rectifying this issue was rewarding, I've invested substantial time into this response due to the lockdown restrictions :D)

Answer 3

Answer №2

After some experimentation, I decided to let CSS handle the rotation transition by setting a randomized angle of rotation based on a floored random value. The result is that the animation stops precisely at the center of the pin. It's now up to you to determine where it landed and assign a score.

var force = 0;
var angle = 0;
var rota = 1;
var inertia = 0.985;
var minForce = 15;
var randForce = 15;
var rouletteElem = document.getElementsByClassName('roulette_wheel')[0];
var scoreElem = document.getElementById('score');

var values = [
  "Spititual", "Emotional", "Intellectual", "Physical", "Social", "Environmental", "Financial"
].reverse();

function roulette_spin(btn) {
  var additionalRotation = Math.floor(Math.random() * values.length) * 360
  angle += additionalRotation;
  rouletteElem.style.transform = 'rotate(' + angle + 'deg)';
}

.roulette_center:hover {
  transform: scale(1.01);
}
.roulette_wheel {
  transition: ease-in-out 3s transform;
}

<div style="z-index: 0; position: relative">
  <span style="position: absolute; top: 0px; left: 360px; font-weight:700;font-size:24px;" id="score">&nbsp;</span>
  <img class="roulette_wheel" src="https://www.dropbox.com/s/6kp3fmtp72aj3vy/wellness-wheel.png?raw=1" />
  <img class="roulette_center" style="position:absolute;left:2px;cursor:pointer;" src="https://www.dropbox.com/s/52x8iyb1nvkjm0w/wheelCenter.png?raw=1" onclick="roulette_spin(this)" onfocus="transform()">
  <div style="position: absolute; top: 30px; left: 350px; background-color: red; width: 1px; height: 60px;"></div>

</div>

Answer 4

After some experimentation, I decided to let CSS handle the rotation transition by setting a randomized angle of rotation based on a floored random value. The result is that the animation stops precisely at the center of the pin. It's now up to you to determine where it landed and assign a score.

var force = 0;
var angle = 0;
var rota = 1;
var inertia = 0.985;
var minForce = 15;
var randForce = 15;
var rouletteElem = document.getElementsByClassName('roulette_wheel')[0];
var scoreElem = document.getElementById('score');

var values = [
  "Spititual", "Emotional", "Intellectual", "Physical", "Social", "Environmental", "Financial"
].reverse();

function roulette_spin(btn) {
  var additionalRotation = Math.floor(Math.random() * values.length) * 360
  angle += additionalRotation;
  rouletteElem.style.transform = 'rotate(' + angle + 'deg)';
}

.roulette_center:hover {
  transform: scale(1.01);
}
.roulette_wheel {
  transition: ease-in-out 3s transform;
}

<div style="z-index: 0; position: relative">
  <span style="position: absolute; top: 0px; left: 360px; font-weight:700;font-size:24px;" id="score">&nbsp;</span>
  <img class="roulette_wheel" src="https://www.dropbox.com/s/6kp3fmtp72aj3vy/wellness-wheel.png?raw=1" />
  <img class="roulette_center" style="position:absolute;left:2px;cursor:pointer;" src="https://www.dropbox.com/s/52x8iyb1nvkjm0w/wheelCenter.png?raw=1" onclick="roulette_spin(this)" onfocus="transform()">
  <div style="position: absolute; top: 30px; left: 350px; background-color: red; width: 1px; height: 60px;"></div>

</div>

Answer 5

Answer №3

To ensure your angle adjustments remain within your current function while utilizing your scoring system effectively, you can determine the closest 1/7th position relative to your current angle at any given moment. This allows you to gauge how near or far you are from a 1/7th segment at any point in time. Assuming your graphic is configured to commence at the top 1/7th and in the middle of the initial section at the top, you can utilize the angle_difference method to manipulate your angle variable accordingly. For instance, you could gradually approach the nearest 1/7th segment when force < 1.0 by dividing the angle_difference into incremental steps instead of immediately adjusting your new angle with (angle + force) % 360.

Here's an illustrative code snippet:

if (force < 1.0) {
    closest_seventh = Math.round(7*(angle/360))*(1/7);
    closest_seventh_angle = 360 * closest_seventh;
    angle_difference = abs(angle - closest_seventh);
    angle_step = angle_difference / 10; // arbitrarily chosen number of steps
    if (angle - closest_seventh < 0) {
        angle = angle - angle_step;
    } else {
        angle = angle + angle_step;
    }
    force = force - (0.5 / 10);
    if (force < 0.05) {
      // approximate score calculation
      scoreElem.innerHTML = values[Math.floor(((angle / 360) * values.length) - 0.5)];
      return;
    }
    requestAnimationFrame(doAnimation);

You can customize the arbitrary values as needed to achieve the desired animation effect, but this concept encompasses:

Awaits until force diminishes to a level before scoring
Determines the closest 1/7th segment once force drops below 1.0
Evaluates the distance to that segment
Calculates the degree increment required for the image to rotate towards the target
Adjusts both force and angle based on the specified number of steps (determined by you), leading to rotation until force reaches below 0.5 and a score is attained.

Some minor tweaks may be necessary when altering the force value for cases where Force > 1.0, but this approach offers a fresh perspective on reaching the central area of your wheel segments.

UPDATE

I overlooked one line of code involving multiplying the closest 1/7th value by 360 to identify the target angle for positioning within the pie piece's center, which has now been incorporated into the code.

Answer 6

To ensure your angle adjustments remain within your current function while utilizing your scoring system effectively, you can determine the closest 1/7th position relative to your current angle at any given moment. This allows you to gauge how near or far you are from a 1/7th segment at any point in time. Assuming your graphic is configured to commence at the top 1/7th and in the middle of the initial section at the top, you can utilize the angle_difference method to manipulate your angle variable accordingly. For instance, you could gradually approach the nearest 1/7th segment when force < 1.0 by dividing the angle_difference into incremental steps instead of immediately adjusting your new angle with (angle + force) % 360.

Here's an illustrative code snippet:

if (force < 1.0) {
    closest_seventh = Math.round(7*(angle/360))*(1/7);
    closest_seventh_angle = 360 * closest_seventh;
    angle_difference = abs(angle - closest_seventh);
    angle_step = angle_difference / 10; // arbitrarily chosen number of steps
    if (angle - closest_seventh < 0) {
        angle = angle - angle_step;
    } else {
        angle = angle + angle_step;
    }
    force = force - (0.5 / 10);
    if (force < 0.05) {
      // approximate score calculation
      scoreElem.innerHTML = values[Math.floor(((angle / 360) * values.length) - 0.5)];
      return;
    }
    requestAnimationFrame(doAnimation);

You can customize the arbitrary values as needed to achieve the desired animation effect, but this concept encompasses:

Awaits until force diminishes to a level before scoring
Determines the closest 1/7th segment once force drops below 1.0
Evaluates the distance to that segment
Calculates the degree increment required for the image to rotate towards the target
Adjusts both force and angle based on the specified number of steps (determined by you), leading to rotation until force reaches below 0.5 and a score is attained.

Some minor tweaks may be necessary when altering the force value for cases where Force > 1.0, but this approach offers a fresh perspective on reaching the central area of your wheel segments.

UPDATE

I overlooked one line of code involving multiplying the closest 1/7th value by 360 to identify the target angle for positioning within the pie piece's center, which has now been incorporated into the code.

How to use JavaScript to create a spinning wheel that stops automatically at the center of a randomly selected slice

Answer №1

Answer №2

Answer №3

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