Question

I am just staring with processing.js and I have been having trouble because every time I rotate an image it also changes its location on the screen. So what processing seems to do is, rotate my image around the point I told it to place it, instead of rotating it first around its own axis and then placing it where I told it to (which I figured cannot be done in that way/order).

This is the code

PShape s;
float angle = 0.1; //rads
s = loadShape("sensor.svg");
s.rotate(angle);
//I change this angle manually or with my clickMouse function which isnt shown.

void setup(){
    size(400,350);
frameRate(30); //30 frames per seconds
}

void draw(){ //shape( shape, x, y, width, height);
    smooth();
    fill(153);
    ellipse(200, 350/2, 100, 100);
    shape(s, 200, 350/2, 20, 20);
    ellipse(200, 350/2, 2, 2);
}

What I am basically trying to do is make this “sensor” image rotate in the correct orientation around the circle (ellipse) that I drew. Thats the idea. Its doing neither. Maybe having a click function that rotates the SVG image around the circle. But instead it rotates around the coordinates of the shape(image, x_coord, y_coord, width, height) function. If anyone has any suggestions, I would be so happy! Hope my question makes sense, if it doesnt I would be more than happy to clarify any part of it.

Thanks! 🙂

Answer 1

It’s much easier not to rotate your shape, but to rotate the coordinate system.

void draw() {
  translate(s.width/2,s.height/2);
  rotate(PI/4);
  shape(s);
  resetMatrix();
  // keep on drawing here
}

This first moves the coordinate system so that (0,0) is on top of the center of your shape, then rotates the entire coordinate system by 45 degrees, then draws your shape. Then you reset the coordinate system and keep drawing as usual.