【Processing入门】第四章:响应互动

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(1) mouseX，mouseY控制图形的移动

void setup(){  background(200);  size(300,300);  smooth();}void draw(){  fill(255,255,0);  rect(mouseX,mouseY,50,50);}

还可以控制图形的大小形状

void setup(){  size(300,300);  smooth();}void draw(){  background(200);  stroke(0);  float d=dist(mouseX,mouseY,150,150);  strokeWeight(d/15);  fill(255);  ellipse(150,150,d*2,d);  strokeWeight(d/20);  fill(255,200,0);  ellipse(150,150,d,d);  fill(0);  noStroke();  ellipse(150,150,d/3,d/3);}

(2)pmouseX,pmouseY也是一对系统变量，是指相对当前鼠标坐标点的上一个坐标位置

void setup(){  size(300,300);  strokeWeight(5);  smooth();  stroke(255,0,80,100);  background(0);}void draw(){  float k=dist(mouseX,mouseY,pmouseX,pmouseY);  strokeWeight(k);   if(mousePressed) {   line(mouseX,mouseY,pmouseX,pmouseY); }

(3)mousePressed

void setup(){  size(300,300);  strokeWeight(5);  smooth();  stroke(255,0,80,100);  background(0);}void draw(){}void mousePressed(){  stroke(0);  fill(255,255,0);  ellipse(mouseX,mouseY,25,25);}

等价于

<p>void setup(){  size(300,300);  strokeWeight(5);  smooth();  stroke(255,0,80,100);  background(0);}</p><p>void draw(){  if(mousePressed)  {  stroke(0);  fill(255,255,0);  ellipse(mouseX,mouseY,25,25);  }}</p>

(4)mouseMoved,mouseDragged

void setup(){  size(300,300);  background(255);  stroke(0,50);  smooth();}void draw(){}void mouseMoved(){  rectMode(CENTER);  fill(255,255,0,50);  rect(mouseX,mouseY,50,50);}void mouseDragged(){  fill(255,100,0,50);  ellipse(mouseX,mouseY,50,50);}

void setup(){  size(300,300);  smooth();  background(204);  rectMode(CENTER);}void draw(){  if(mousePressed)  {    if(mouseButton == LEFT)     {       fill(255);     }     else if(mouseButton == CENTER)     {       fill(0);     }     else     {       fill(100);     }     rect(mouseX,mouseY,50,50);  }}

(5)键盘响应

按击键响应，可以使用void keyPressed(),也可以使用if(keyPressed)。用系统变量指定特定按键，当key为CODED时表示功能键，使用keyCode指定具体的功能键。

void setup(){  size(300,300);  smooth();  strokeWeight(10);  strokeCap(SQUARE);}void draw(){  background(200);  if(keyPressed)  {    if(key == 'a')    {      fill(255,0,0);      rect(100,100,100,100);    }        if(key==CODED && keyCode == UP)    {      fill(255,255,0);      rect(100,100,100,100);    }          }}

(6)随机random

random(),用于产生特定范围的随机数，比如random(1,4)

(7)限制constrain()

constrain(value,min,max)，value指要限定的变量值

如

constrain(mouseX,100,400);

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