mirror of
https://github.com/photonstorm/phaser
synced 2024-11-24 05:33:35 +00:00
36 lines
1,007 B
JavaScript
36 lines
1,007 B
JavaScript
/**
|
|
* Convert a distance along this curve into a `time` value which will be between 0 and 1.
|
|
*
|
|
* For example if this curve has a length of 100 pixels then `findT(50)` would return `0.5`.
|
|
*
|
|
* @param {integer} distance - The distance into the curve in pixels. Should be a positive integer.
|
|
* @return {number} The time (`t`) value, a float between 0 and 1.
|
|
*/
|
|
var FindT = function (curve, distance)
|
|
{
|
|
if (distance <= 0)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
// Find the _points which bracket the distance value
|
|
var ti = Math.floor(distance / curve.length * curve._accuracy);
|
|
|
|
while (ti > 0 && curve._points[ti] > distance)
|
|
{
|
|
ti--;
|
|
}
|
|
|
|
while (ti < curve._accuracy && curve._points[ti] < distance)
|
|
{
|
|
ti++;
|
|
}
|
|
|
|
// Linear interpolation to get a more accurate fix
|
|
var dt = curve._points[ti] - curve._points[ti - 1];
|
|
var d = distance - curve._points[ti - 1];
|
|
|
|
return ((ti - 1) / curve._accuracy) + d / (dt * curve._accuracy);
|
|
};
|
|
|
|
module.exports = FindT;
|