Is there a 1 dimensional CreateCatmullRomSpline type function?

TheSkrapper · January 31, 2021, 10:38pm

Hello,

This is a general question is about optimizing my current code logic if possible.

I’ve been using CreateCatmullRomSpline to shape some of my data. The pertinent data originates in a one dimensional array which is all I am really interested in (call it y). I want to insert one data value between each existing value to double my data set but using the average of the neighbors doesn’t produce the desired smooth result.

I currently convert this data into a points array of Vector3(index, y, 0) and feed this points array into CreateCatmullRomSpline only to turn around and just pull all the Y values back out again. This produces the desired smoothing result.

Is there a more optimal way to achieve the same result using just the original one dimensional array? My math isn’t the strongest so I think I may just be missing some basic math function that does the same.

Thanks for any feedback.

TheSkrapper

Evgeni_Popov · February 1, 2021, 10:44am

I think the easiest way is to copy the source code from this function into your project and adapt it to compute only the y values:

github.com

BabylonJS/Babylon.js/blob/master/src/Maths/math.path.ts#L885-L915


public static CreateCatmullRomSpline(points: DeepImmutable<Vector3[]>, nbPoints: number, closed?: boolean): Curve3 {
    var catmullRom = new Array<Vector3>();
    var step = 1.0 / nbPoints;
    var amount = 0.0;
    if (closed) {
        var pointsCount = points.length;
        for (var i = 0; i < pointsCount; i++) {
            amount = 0;
            for (var c = 0; c < nbPoints; c++) {
                catmullRom.push(Vector3.CatmullRom(points[i % pointsCount], points[(i + 1) % pointsCount], points[(i + 2) % pointsCount], points[(i + 3) % pointsCount], amount));
                amount += step;
            }
        }
        catmullRom.push(catmullRom[0]);
    } else {
        var totalPoints = new Array<Vector3>();
        totalPoints.push(points[0].clone());
        Array.prototype.push.apply(totalPoints, points);
        totalPoints.push(points[points.length - 1].clone());
        for (var i = 0; i < totalPoints.length - 3; i++) {

This file has been truncated. show original

github.com

BabylonJS/Babylon.js/blob/master/src/Maths/math.vector.ts#L1666-L1683


public static CatmullRom(value1: DeepImmutable<Vector3>, value2: DeepImmutable<Vector3>, value3: DeepImmutable<Vector3>, value4: DeepImmutable<Vector3>, amount: number): Vector3 {
    var squared = amount * amount;
    var cubed = amount * squared;

    var x = 0.5 * ((((2.0 * value2._x) + ((-value1._x + value3._x) * amount)) +
        (((((2.0 * value1._x) - (5.0 * value2._x)) + (4.0 * value3._x)) - value4._x) * squared)) +
        ((((-value1._x + (3.0 * value2._x)) - (3.0 * value3._x)) + value4._x) * cubed));

    var y = 0.5 * ((((2.0 * value2._y) + ((-value1._y + value3._y) * amount)) +
        (((((2.0 * value1._y) - (5.0 * value2._y)) + (4.0 * value3._y)) - value4._y) * squared)) +
        ((((-value1._y + (3.0 * value2._y)) - (3.0 * value3._y)) + value4._y) * cubed));

    var z = 0.5 * ((((2.0 * value2._z) + ((-value1._z + value3._z) * amount)) +
        (((((2.0 * value1._z) - (5.0 * value2._z)) + (4.0 * value3._z)) - value4._z) * squared)) +
        ((((-value1._z + (3.0 * value2._z)) - (3.0 * value3._z)) + value4._z) * cubed));

    return new Vector3(x, y, z);
}

It seems the computation of x/y/z are independent, so you can remove the ones for x/z.

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Is there a 1 dimensional CreateCatmullRomSpline type function?

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