Rotate () like earth around sun

Processing Coding Questions
1

Hello every one…
Is it possible to rotate an object around imself and around a other point on the same time?
Thank’s a lot.

2

The easiest way to do this would probably be to apply two translate and two rotate transformations to your object (or planet, in your case), like this:

translate(centerX, centerY); // move anchor point to the center
rotate(rotation1);           // rotate the planet around the center
translate(distanceToCenter); // move anchor point to planet position
rotate(rotation2);           // rotate planet around itself

You would then increment the rotations every frame.
However this only works if you want the planet to follow a circle. Real planets move on elliptical paths. If you want to have this behavior, you’ll need to use cos and sin.

3

Thank’s it’s working

4

Hello,

My “quick” initial approach to this…

float x, y;
float theta1;
int i;
float a, b;

void setup() 
  {
  size(700, 500);
  a = 200;
  b = 150;
  }

void draw() 
 {
  background(0);
  translate(width/2, height/2);
  i++;
  theta1 = i*TAU/500;  
  x = a*cos(theta1);
  y = b*sin(theta1);
  strokeWeight(10);
  stroke(255, 255, 0);
  point(x, y);
  
  // Additional code; similar to above but new orbits were translated OR added to previous points.
  }

I started with the above code and kept adding additional orbits around the rotating point.

image
image702×527 3.12 KB

:slight_smile:

5

You could maybe use a PVector with the distance as x, y as 0, and then rotate this Vector.

PVector rotation;

void setup() {
  size(400, 400);
  rotation = new PVector(50, 0);
}

void draw() {
  translate(width/2, height/2);

  noStroke();
  fill(255, 220, 0);
  ellipse(0, 0, 20, 20);

  fill(0, 255, 50);
  ellipse(rotation.x, rotation.y, 20, 20);

  rotation.rotate(radians(1));
}
6

Thank a lot it’s work like this