Hello

I have a method which moves a sphere on a spline of type Curve3.

So I have a snippet of code, which work well in JS in the playground I’ve implemented before moving to TS, and is taken from the “follow path” tutorial.

Since I’ve transformed it to TS it gives me “undefined” errors of many kinds.

The location of the error is at the line: `this._sphere.position = this.pathPoints[i];`

What is wrong with this code?

```
private async _prepareTrailEffect(spline: Curve3, splineMesh: Mesh, startPosition: Vector3) {
this._sphere.setParent(splineMesh);
this._sphere.position = startPosition;
var pathPoints = spline.getPoints();
Logger.Warn("path point count" + pathPoints.length);
var numberOfPoints = pathPoints.length;
var path3d = new Path3D(pathPoints);
var normals = path3d.getNormals();
var theta = Math.acos(Vector3.Dot(Axis.Z, normals[0]));
var i = 0;
this.scene.registerAfterRender(function () {
this._sphere.position = this.pathPoints[i];
theta = Math.acos(Vector3.Dot(normals[i], normals[i + 1]));
var direction = Vector3.Cross(normals[i], normals[i + 1]).y;
var direction = direction / Math.abs(direction);
this._sphere.rotate(Axis.Y, direction * theta, Space.WORLD);
i = (i + 1) % (numberOfPoints - 1);
});
}
```

So I tried to use For Loop

```
for (var i = 0; i < numberOfPoints; i++) {
this.scene.registerAfterRender(function () {
this._sphere.position = this.pathPoints[i];
theta = Math.acos(Vector3.Dot(normals[i], normals[i + 1]));
var direction = Vector3.Cross(normals[i], normals[i + 1]).y;
var direction = direction / Math.abs(direction);
this._sphere.rotate(Axis.Y, direction * theta, Space.WORLD);
});
}
```

The goal is to wait until the end of frame and then increase the index by 1.

What would be the preferred way to do so in TS?

Thanks