【Processing入门】第四章:响应互动

(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);