# Vector3

geometrycentral::Vector3 is the basic 3D vector type in geometry central. There are many like it, but this one is ours.

#include "geometrycentral/vector3.h"

### Construction

Vector3 is a POD type, so you should use brace-initialization sytax:

#include "geometrycentral/vector3.h
using namespace geometrycentral;

Vector3 myVec{3.8, 2.9, 1.1}; //create
myVec = Vector3{1.1, 2.2, 3.3}; // reassign


Factory methods can construct a few common values:

static Vector3 Vector3::zero()

Returns the zero vector

static Vector3 Vector3::constant(double c)

Returns a vector with all components set to $c$

static Vector3 Vector3::infinity()

Returns the infinite vector $(\infty, \infty, \infty)$.

static Vector3 Vector3::undefined()

Returns the undefined vector (NaN, NaN, NaN).

### Access

The three elements of the vector can be accessed as vec.x and vec.y and vec.z.

Alternately, the elements can be indexed as vec[0] and vec[1] and vec[2].

### Conversion

Vector3::operator<<()

Vector3 can be serialized.

Vector3 v{1.2, 3.4, 5.6};
std::cout << v << std::endl;
// prints something like: <1.2, 3.4, 5.6>


### Arithmetic

Vector3 supports the element-wise addition, subtraction, and scalar multiplication you would probably expect.

### Member operations

These methods do not change the underlying Vector3, but return a new Vector3.

Vector3 vec{1., 2., 3.};
vec.normalize();        // does nothing
vec = vec.normalize();  // much better


Vector3 Vector3::normalize()

Returns a unit-norm vector pointing in the same direction. If the input is the zero vector, the result will contain NaNs.

Vector3 Vector3::rotateAround(Vector3 axis, double theta)

Rotate the vector by angle $\theta$ around axis in the right-handed direction. axis need not be a unit vector.

Vector3 Vector3::removeComponent(Vector3 unitDir)

Removes any component of this vector in the direction unitDir, making the result orthogonal to unitDir. As the name suggests, unitDir must be a unit vector.

double Vector3::norm()

Returns the magnitude of the vector.

Also available as norm(v).

double Vector3::norm2()

Returns the squared magnitude of the vector.

Also available as norm2(v).

### Function operations

These operations do not change the vector on which they are called.

double norm(Vector3 v)

Returns the magnitude of the vector.

Also available as v.norm().

double norm2(Vector3 v)

Returns the squared magnitude of the vector.

Also available as v.norm2().

Vector3 unit(Vector3 v)

Returns normalized copy of the vector.

double dot(Vector3 u, Vector3 v)

Returns the dot product between two vectors.

double sum(Vector3 u)

Returns the sum of the coordinates of a vector

Vector3 cross(Vector3 u, Vector3 v)

Returns the cross product between two vectors.

double angle(Vector3 u, Vector3 v)

Returns the angle between two not-necessarily-unit vectors. Output in the range $[0, \pi]$.

double angleInPlane(Vector3 u, Vector3 v, Vector3 normal)

Returns the signed angle between two not-necessarily-unit vectors, measured in the plane defined by normal (which need not be a unit vector). Output is in the range $[-\pi, \pi]$, as in atan2.

Vector3 clamp(Vector3 val, Vector3 low, Vector3 high)

Returns returns a a vector where each component has been clamped to be between the corresponding compnents of low and high.

Vector3 componentwiseMin(Vector3 u, Vector3 v)

Returns a new vector, each component of which is the minimum of that component in u and v.

Vector3 componentwiseMax(Vector3 u, Vector3 v)

Returns a new vector, each component of which is the maximum of that component in u and v.

### Properties

bool isfinite(Vector3 u)

Returns true if all of the components of the vector are finite.

Note: this function is intentionally not camel-cased out of solidarity with std::isfinite().

Also available as u.isFinite().

bool isDefined(Vector3 u)

Returns true if all of the components of the vector are not NaN.

Also available as u.isDefined().