How to understand Translate() function?

zheng

I am confused about translate() function.

PImage bird;
float x,y;
float rot;

void setup(){
size(500,500);
bird= loadImage("bird.png");
x= 100;
y=100;
rot =0;
}
void draw(){
  background(255);
  pushMatrix();

  translate(x+bird.width/2,y+bird.height/2);
      rotate(rot);

  translate(-bird.width/2,-bird.height/2);
image(bird,0,0);

popMatrix();
rot = rot+0.1;

}

quark

The translate statement simply moves the origin [0,0] for drawing commands from the top-left corner to a new position.

quark

The code you posted is a little awkward because I assume you wish to display the image centered and rotated about position [x,y]. This is more easily achieved by changing the imageMode to CENTER like this.

PImage bird;
float x, y;
float rot;

void setup() {
  size(500, 500);
  imageMode(CENTER);
  bird= loadImage("bird.png");
  x= 100;
  y=100;
  rot =0;
}
void draw() {
  background(255);
  pushMatrix();

  translate(x, y);
  rotate(rot);
  image(bird, 0, 0);

  popMatrix();
  rot = rot+0.1;
}

zheng

@quark Thanks a lot!