Rotating/Translation of multiple objects around center

bobhaha

Hey guys,

Am I doing something wrong here? I seem to always get a Y axis offset when rotating a rect around its center.... here is my code.

void setup(){  
 size(1200,800); 
 smooth();
 rectMode(CENTER);
}

void draw(){

  //Draw screen
  background(255);
  line(width/2,0, width/2,height);
  line(0,height/2, width,height/2);

  //First Square
  pushMatrix();
  fill(0);
  translate(width/2, height/2);
  rotate(0.2);
  translate(-300,60);
  rect(0,0, 120,120, 25);
  popMatrix();

  //Second Square
  pushMatrix();
  fill(200);
  translate(width/2,height/2);
  rotate(0.6);
  translate(300,-60);
  rect(0,0, 120,120, 25);
  popMatrix();

}

First square is rotated by 0.2rad and works fine, second square is rotated 0.6rad and it's got a weird Y axis offset. Not sure why this is happening.

Any help is appreciated!

Chrisir

you need to place your rect on the origin

so it's rect (-60,-60,120,120);

otherwise you rotate around the top left corner

bobhaha

You mean like this?

  pushMatrix();
  fill(0);
  translate(width/2, height/2);
  rotate(0.2);
  translate(-300,60);
  rect(-60,-60, 120,120, 25);
  popMatrix();

If so... no good. I set rotation to 0, adjusted the second translation so it will be in the right place.... then if I put in any rotation angle it doesn't rotate in place. Seems to be rotating around the center of screen.

Chrisir

this:

 translate(300,-60);

should be

 translate(300,60);

Chrisir

float a=0.0; 

void setup() {  
  size(1200, 800); 
  smooth();
  rectMode(CENTER);
}

void draw() {

  //Draw screen
  background(255);
  line(width/2, 0, width/2, height);
  line(0, height/2, width, height/2);

  //First Square
  pushMatrix();
  fill(0);
  translate(width/2, height/2);
  translate(-300, 60);
  rotate(a);  
  rect(0, 0, 120, 120, 25);
  popMatrix();

  //Second Square
  pushMatrix();
  fill(200);
  translate(width/2, height/2);
  translate(300, 60);
  rotate(a);  
  rect(0, 0, 120, 120, 25);
  popMatrix();

  a+=.01;
}

bobhaha

Ah dang, I was so close! Thanks so much Chrisir!