Changing the centre of rotation of a 3D object

Lloyd

what function can be used in a programming code to move the centre of rotation from centre of sketch to centre of the 3D object. For eg A stick not rotating on its end but its centre

TfGuy44

translate()

https://processing.org/tutorials/transform2d/

TfGuy44

void setup() {
  size(440, 440, P3D);

}

void draw() {
  background(0);
  translate(width/2, height/2, 0);
  lights();
  rotateX(map(mouseY,0,height,-PI,PI));
  rotateY(map(mouseX,0,width,-PI,PI));
  fill(255);
  noStroke();
  box(30);
  stroke(255,0,0);
  line(0,0,0,100,0,0);
  stroke(0,255,0);
  line(0,0,0,0,100,0);
  stroke(0,0,255);
  line(0,0,0,0,0,100);

  translate(100,100,100);
  noFill();
  stroke(0,255,255);
  box(5);
  rotateX(map(millis()%5000,0,5000,0,TWO_PI));
  rotateY(map(millis()%7000,0,7000,0,TWO_PI));
  stroke(255);
  translate(-50,0,0);
  line(0,0,0,100,0,0);
}

jeremydouglass

translate() is the general purpose way to solve these problems -- in addition, for built-in shapes, you can set the mode to centered for that shape type -- rectMode(), ellipseMode() etc.

Chrisir

You can isolate rotations with pushMatrix and popMatrix

Lloyd

translate moves the freedom of rotation to wherever u want on the screen but what if we want to rotate about the centre of the irregular body shape like a rock or something

jeremydouglass

Just draw that irregular object from the center, the same as a regular one. No matter how irregular, it has a center -- width/2, height/2, depth/2.

To center everything / anything with respect to the 3D camera, use the PeasyCam library.