2017
07-19

# PVector 向量

PVector v1, v2;

void setup() {
noLoop();
v1 = new PVector(40, 20);
v2 = new PVector(25, 50);
}

void draw() {
ellipse(v1.x, v1.y, 12, 12);
ellipse(v2.x, v2.y, 12, 12);
ellipse(v2.x, v2.y, 24, 24);
}

 A class to describe a two or three dimensional vector, specifically a Euclidean (also known as geometric) vector. A vector is an entity that has both magnitude and direction. The datatype, however, stores the components of the vector (x,y for 2D, and x,y,z for 3D). The magnitude and direction can be accessed via the methods mag() and heading(). 一个用于描述二维或三维向量，特别是欧几里德（也称为几何）向量的类。向量是具有大小和方向的实体。其数据类型存储向量的分量（x，y为2D，x，y，z为3D）。我们可以通过mag（）和heading（）方法访问大小和方向。 In many of the Processing examples, you will see PVector used to describe a position, velocity, or acceleration. For example, if you consider a rectangle moving across the screen, at any given instant it has a position (a vector that points from the origin to its location), a velocity (the rate at which the object’s position changes per time unit, expressed as a vector), and acceleration (the rate at which the object’s velocity changes per time unit, expressed as a vector). Since vectors represent groupings of values, we cannot simply use traditional addition/multiplication/etc. Instead, we’ll need to do some “vector” math, which is made easy by the methods inside the PVector class. 在许多Processing示例中，您可以看到PVector用于描述位置，速度或加速度。例如，如果您考虑在屏幕上移动一个矩形，则在任何给定的时刻，它都有一个位置（一个从原点到其位置的向量），一个速度（每个时间单位的对象位置变化的速率）作为向量）和加速度（物体的速度随时间变化的速率，表示为向量）。由于向量表示值的分组，我们不能简单地使用传统的加法/乘法等。相反，我们需要做一些“向量”数学，而PVector类中的方法使其变得容易。

x The x component of the vector            向量的x分量 The y component of the vector            向量的y分量 The z component of the vector            向量的z分量

set() Set the components of the vector Make a new 2D unit vector with a random direction. Make a new 3D unit vector with a random direction. Make a new 2D unit vector from an angle Get a copy of the vector Calculate the magnitude of the vector Calculate the magnitude of the vector, squared Adds x, y, and z components to a vector, one vector to another, or two independent vectors Subtract x, y, and z components from a vector, one vector from another, or two independent vectors Multiply a vector by a scalar Divide a vector by a scalar Calculate the distance between two points Calculate the dot product of two vectors Calculate and return the cross product Normalize the vector to a length of 1 Limit the magnitude of the vector Set the magnitude of the vector Calculate the angle of rotation for this vector Rotate the vector by an angle (2D only) Linear interpolate the vector to another vector Calculate and return the angle between two vectors Return a representation of the vector as a float array

```PVector()
PVector(x, y, z)
PVector(x, y)
```

x float: the x coordinate.        x坐标 float: the y coordinate.        y坐标 float: the z coordinate.        z坐标 