libgdx-math

libGDX Math Utilities

Quick reference for com.badlogic.gdx.math.*. Covers vectors, matrices, quaternion, interpolation, intersection/collision, shapes, and math helpers.

CRITICAL: Vectors Mutate In Place

Almost every Vector2/Vector3 method mutates this and returns this for chaining. This is the #1 source of bugs.

Vector2 a = new Vector2(1, 2);
Vector2 b = new Vector2(3, 4);

a.add(b);            // a is now (4, 6) — b unchanged
a.cpy().add(b);      // returns new (4, 6) — a unchanged
a.sub(b).nor();      // a mutated TWICE — subtracted then normalized

This applies to: set(), add(), sub(), scl(), nor(), lerp(), rotate*(), limit(), clamp(), setLength(), mulAdd(), setZero(), setToRandomDirection().

Vector2

new Vector2()                    // (0, 0)
new Vector2(float x, float y)
new Vector2(Vector2 v)           // copy constructor EXISTS

// Static constants (WARNING: mutable — treat as read-only)
Vector2.X   // (1, 0)
Vector2.Y   // (0, 1)
Vector2.Zero // (0, 0)

Key methods beyond the obvious (set, add, sub, scl, nor, lerp, setZero, cpy — all mutating, return this):

• limit(float) / limit2(float) — cap magnitude (limit2 avoids sqrt)
• clamp(float min, float max) — clamp magnitude
• setLength(float) / setLength2(float) — set magnitude
• mulAdd(Vector2, float) — this += vec * scalar
• mul(Matrix3) — transform by Matrix3 only, NOT Matrix4
• crs(Vector2) — returns float (2D cross product is a scalar)
• len2(), dst2() — squared versions (prefer for comparisons, avoids sqrt)

Angle & Rotation (Vector2 only)

Use Deg suffix methods. Non-suffixed versions are deprecated:

• angleDeg() / angleDeg(Vector2 ref) — degrees 0–360
• angleRad() / angleRad(Vector2 ref) — radians
• rotateDeg(float) / rotateRad(float) — rotate vector
• rotateAroundDeg(Vector2 ref, float deg) — rotate around point
• setAngleDeg(float) / setAngleRad(float) — set direction
• rotate90(int dir) — dir >= 0 = CCW, dir < 0 = CW
• DEPRECATED: angle(), rotate(float), setAngle(float), rotateAround(Vector2, float) — use Deg versions