Can MotionPath be made circular, or elliptical?

The topic is in the title. It’d be very useful for such things as making planets travel on an orbit without the fuss of physics. Setting CurveTension to 1 makes an almost-circular path, but it’s not what I’m after.

Any tips before I go code an orbital PathInterpolation?

Hang on, maybe I should just approximate what I’m after with more waypoints. Sorry, guys.

in TestCameraMotionPath i achieved a circular path with 4 waypoints and a tension of about 0.8.

You should check the testcase

Thanks for that! Some easy math and using 20 waypoints per orbit I’m getting near perfect ellipses :smiley:


May I ask you if you could post the code? it could be a useful snippet.


Not sure how snippets work, but here goes:

pre type="java"[java]// This snippet of code takes an x value (X) and an eccentricity value (E), and produces an elliptical path around the origin. It should be straight-forward to adapt to other uses.

float x = (float) X;

// Do calculation from

float y = (float) (X * Math.sqrt(1 - Math.pow(E, 2)));

// Find one of the ellipses foci, to orbit around.

float foci = (float) Math.sqrt(Math.pow((x/2), 2) - Math.pow((y/2), 2));

final float numberOfWaypoints = 20;

MotionPath path = new MotionPath();

for (int i = 0; i < numberOfWaypoints; i++) {

path.addWayPoint(new Vector3f((float) (Math.cos((i * 2 * Math.PI)/numberOfWaypoints) * x) + foci, 0, (float) Math.sin(i * (2 * Math.PI)/numberOfWaypoints) * y));


path.enableDebugShape(assetManager, rootNode);

// Tension might need a little adjusting depending on how many waypoints you want. I think

// 0.5 is acceptable for 20 waypoints.