# Test if two spatials are in right angle

Hello

I have two Spatials (viewerSource, geom) and I want to figure out whether the geom is relative to the viewerSource’s translation and rotation ± a specific angle.

It’s hard to describe without knowing the right words, here’s an image:

I want to test if the target (orange) is between the green lines.

I tried to write some code. My current solution is not right, but I have no idea how to solve that. Can somebody please tell me, how to do that right?

My current code is:

``````final Vector3f viewLocation = tmp.vect1.set(viewerSource.getLocalTranslation());
final Vector3f targetLocation = tmp.vect2.set(geom.getLocalTranslation());

final Vector3f viewDirection = tmp.vect4.set(Vector3f.UNIT_Z);
viewerSource.getLocalRotation().multLocal(viewDirection).normalizeLocal();

final float distanceBetween = tmp.vect5.set(viewLocation).distance(targetLocation);
final Vector3f testLocation = tmp.vect6.set(viewDirection).multLocal(distanceBetween).addLocal(viewLocation);

System.out.println(targetLocation.distance(testLocation));
``````

You can use Vector3f.angleBetween

``````viewDirection;
targetDirection=new Vector3f(targetLocation).substractLocal(viewLocation).normalizeLocal()
angle=viewDirection.angleBetween(targetDirection)
``````
1 Like

lol, I played with dot() and such stuff, but it is soooo easy. xD
Thank you very much.

Angle between is essentially using dot() and then passing it through a (relatively expensive) trig call.

For reference, and presuming this might be for a steering behavior, the typical approach would be to dot with the left vector.

``````Vector3f leftDir = driver.getWorldRotation().mult(Vector3f.UNIT_X);
Vector3f relativeOffset = target.getWorldTranslation().substract(driver.getWorldTranslation());
Vector3f relativeDir = relativeOffset.normalize();
float steer = leftDir.dot(relativeDir);
``````

Where steer will be between -1 and 1 for steering right or left suitable for plugging directly into a steering behavior.

Caveats:
angleBetween() should give you -180 to 180 which is probably desirably for your narrow use-case.
the ‘steer’ approach gives -1 to 1 but that means -90 to 90… things behind you would still need to be detected… but usually for steering you also do an unnormalized dot with the forward vector.

``````float forward = forwardDir.dot(relativeOffset);
``````

…which lets the steering behavior decide if it has arrived yet or if the target is behind them, whether they should turn or back up, etc…

7 Likes

Thank you very much for explaining.

1 Like