Make Vector2.angle and Vector2.angleRad consistent

Current situation

• Vector2.angle() returns values between [0, 360]
• Vector2.angle(Vector2) returns values between [-180, 180]
• Vector2.angleRad() returns values between [-Math.PI, Math.PI]
• Vector2.angleRad(Vector2) returns values between [-Math.PI, Math.PI]

There’s two inconsistencies here.

1. Result range: Why only one of these function returns always positive values, while the 3 others don’t?
2. Naming: Why some function are named with the angle unit, and not the others?

Proposition:

1. Add angleDeg() and angleDeg(Vetor2) functions returning both values between [-180, +180]
2. Deprecate angle() and angle(Vector2) functions

This would make usage of angles in radians and degrees more consistent. Conversions would also be easier, since multiplying by MathUtils.degreeToRadians or MathUtils.radiansToDegree would always be enough.

Reproduction steps/code

This:

System.out.println(new Vector.2(0f, -1f).angleDeg()); // -90
System.out.println(new Vector.2(0f, -1f).angleRad()); // -Math.PI / 2

Would be preferable to:

System.out.println(new Vector.2(0f, -1f).angle()); // 270
System.out.println(new Vector.2(0f, -1f).angleRad()); // -Math.PI / 2

Version of LibGDX and/or relevant dependencies

1.9.8

Please select the affected platforms

Platform is irrelevant here. This is math.

[obigu]

In the 2D world and the non engineering specialised world everybody is used to work in the [0º,360º] range and this is how it works across most libGDX classes ranging from Math utils classes, to Camera, etc… The word convention means that is what people usually use, nothing else, you won’t find a statement online, just ask anybody how they usually work in 2D geometry.

I don’t know about 3D engines Unity and Unreal but those 2 links you provide don’t proof all the functions on the engine work on that range (here’s for example a link to a class that works on the [0,360] https://docs.unity3d.com/ScriptReference/Transform-eulerAngles.html). Even if they did though, it doesn’t matter, we can do better/simpler because Vector2 is 2D only.

[jcornaz]

I aggree it is not a “big deal”. I’m only saying it can be better.

However, we probably not have the same definition of “beginner friendly”. I find it very difficult for a beginner to understand why none of angle(), angle(Vector2), angle() and angleRad(Vector2) behave consistently. It would be so much simpler to get started if theses functions would be consistent.

The current behavior is:

• angle() returns between [0, 360] toward +y
• angle(Vector2) returns between [-180, 180] toward -y
• angleRad() returns between [-Math.PI, Math.PI] toward +y
• angleRad(Vector2) returns between [-Math.PI, Math.PI] toward -y

Do you really find that “beginner friendly”?

My conception of “beginner friendly” would be more:

• angle() returns between [-180, 180] toward +y
• angle(Vector2) returns between [-180, 180] toward +y
• angleRad() returns between [-Math.PI, Math.PI] toward +y
• angleRad(Vector2) returns between [-Math.PI, Math.PI] toward +y

user code may rely on it.

That’s why I don’t propose to change it, but to deprecate it and provide an alternative.